Name: qualitative analysis for ion identification
Uploaded: 2023-04-30T06:45:24.000Z
Duration: 9 min 9 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.6.2

determining-the-solubility-rules-of-ionic-compounds

Determining the Solubility Rules of Ionic Compounds

1. General Methods
<ol>
	<li>Preparing for Qualitative Analysis
	<ol>
		<li>Reactions are generally done in small test tubes with volume of 5 mL or less.</li>
		<li>Solutions need to be fully soluble and should be relatively dilute, typically ~0.1 M.</li>
		<li>Reagents should be slowly added drop-wise and observed carefully.</li>
		<li>Several common &#34;test solutions&#34; are required to establish solubility rules or identify an unknown ion. These contain ions known to react specifically with certain chemical species (cations or anions).
		<ol>
			<li>Common solutions include CaNO3, BaCl2, (NH4)2MoO4, HCl, AgNO3, and NaOH, and other solutions as needed.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Mixing
	<ol>
		<li>Mix solutions by tapping or swirling the test tube in a vertical direction. Use a cork or stopper to prevent splashing the solution.</li>
		<li>Remove the cork or stopper, then gently heat the solutions with a water bath or cool flame to induce a reaction. Point the test tube away from any individuals in the lab.</li>
	</ol>
	</li>
	<li>Observation and Recovery
	<ol>
		<li>Separate the supernatant (non-reacting solution) and precipitate using centrifugation. If more precipitate forms when additional test ion is added, the reaction is incomplete. Continue adding test ion until no more precipitate forms.</li>
		<li>Wash the precipitate using centrifugation and pouring or decanting off the supernatant. Add more water and repeat the process for a total of three washings.</li>
		<li>Wash large quantities of precipitate by vacuum filtration and recover the dried precipitate from the filter paper.</li>
		<li>Note the formation of a precipitate as well as the properties of the precipitate such as color, thickness (gelatinous, cloudy, fine), and crystal formation.</li>
	</ol>
	</li>
	<li>Safety and Waste
	<ol>
		<li>Always wear safety eyewear while performing qualitative analysis experiments. Gloves may also be necessary based on the reagents used and products formed.</li>
		<li>Proper waste disposal methods must be followed closely. Harmful products can be formed when multiple reactants are combined in one container.</li>
	</ol>
	</li>
</ol>
2. Anion Analysis
<ol>
	<li>Identifying phosphate, carbonate, chloride, and sulfide ions; PO43-, CO32-, Cl-, S2-
	<ol>
		<li>Phosphate
		<ol>
			<li>Add a solution containing phosphate, PO43-, to another solution containing calcium ions, Ca2+. The formation of a white precipitate indicates the formation of calcium phosphate, Ca3(PO4)2.</li>
			<li>Since many cations form insoluble products with calcium, a more specific reaction is possible. Add H+ (acid) to Ca3(PO4)2 to dissolve the solid and form HPO42-. Then combine the HPO42- with ammonium molybdate, (NH4)2MoO4. A positive test yields the yellow precipitate ammonium phosphomolybdate, NH4)3PO4(MoO3)12(s). The net ionic reactions are as follows: 
			3 Ca2+(aq) + 2 PO43-(aq) &#8594; Ca3PO4(s) 
			Ca3PO4(s) + 2 H+(aq) &#8594; 3 Ca2+ + 2 HPO42-(aq) 
			HPO42-(aq) + 12 (NH4)2MoO4(aq) + 23 H+(aq) &#8594; (NH4)3PO4 (MoO3)12(s) + 21 NH4+(aq) + 12 H2O(l)&#160;</li>
		</ol>
		</li>
		<li>Carbonate
		<ol>
			<li>Carbonate salts are generally insoluble except in the presence of Group 1 and ammonium cations. Add a few drops of calcium chloride, CaCl2, to the carbonate-containing solution. In solutions with high carbonate concentrations, a white precipitate forms and indicates the possible formation of calcium phosphate, CaCO3. The reaction has many interferences, including other anions like phosphate. 
			Ca2+(aq) + CO32-(aq) &#8594; CaCO3(s)&#160;</li>
			<li>Add H+ (acid) to a solution containing carbonate, CO32-. The formation of bubbles indicates presence of CO2, signifying CO32- as a reactant. Carbonate ion behaves as a base in the presence of strong acid to form carbon dioxide gas and water. 
			CO32-(aq) + H+(aq) &#8594; CO2(g) + H2O(l)</li>
		</ol>
		</li>
		<li>Chloride
		<ol>
			<li>Add silver nitrate to a chloride-containing solution. The formation of a white precipitate indicates the formation of AgCl(s): 
			Ag+(aq) + Cl-(aq) &#8594; AgCl(s)</li>
		</ol>
		</li>
		<li>Sulfide
		<ol>
			<li>Add a copper chloride solution to a solution containing sulfide. The formation of a black precipitate indicates the formation of copper sulfide, CuS. In general, solutions containing sulfide ions, S2-, react with metal ions to yield an insoluble metal sulfide. 
			S2- + Cu2+ &#8594; CuS(s).&#160; 
			The value of the solubility product, Ksp = 6.3 x 10-36, indicates the high degree of insolubility of the product.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>
3. Cation Analysis
<ol>
	<li>All alkali metals (group 1) and some alkaline earth metals (group 2) are soluble except under specific conditions.</li>
	<li>Nearly all Group 3&#8211;13 metals are considered insoluble in the presence of sulfide, carbonate, phosphate, and hydroxide. The color and type of precipitate will vary.
	<ol>
		<li>Place a chromium solution in a hydroxide solution. A green precipitate will be observed. The general reaction of a +2 metal with a hydroxide is shown below: 
		M2+ + OH- &#8594; M(OH)2(s)</li>
		<li>It is not possible to differentiate most metal ions based on solubility alone with some notable exceptions:
		<ol>
			<li>The addition of silver, Ag+, mercury, Hg22+, or lead, Pb2+ to chloride, bromide, or iodide results in precipitate formation.</li>
			<li>The addition of strontium, Sr2+, barium, Ba2+, mercury, Hg22+, or lead, Pb2+ results in a precipitate in the presence of sulfate.</li>
			<li>Ba2+ forms a yellow solid in the presence of CrO42-, BaCrO4(s). This is pigment used in oil-based paint commonly known as &#34;barium yellow&#34;.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Limited insolubility of metal ions allows for other qualitative tests to positively identify each metal. While some form precipitates, others undergo unique color changes in the presence of chelating ions or molecules. Cation identifications include nickel, iron, aluminum, and zinc; Ni2+, Fe3+, Al3+, Zn2+.
	<ol>
		<li>Add nickel (II) in the presence of dimethylglyoxime (H2dmg) to form the rose-red precipitate Ni(H2dmg): 
		Ni2+(aq) + 2 H2dmg(aq) &#8594; Ni(Hdmg)2(s) + 2 H+(aq)&#160;</li>
		<li>Add Iron (III) to thiocyanate ion, SCN- to form the blood-red [FeNCS]2+] complex: 
		Fe3+(aq) + SCN-(aq) &#8594; [FeNCS]2+(aq)</li>
		<li>Aluminum ion
		<ol>
			<li>Combine aluminum (III) with pyrocatechol violet in a pH 6 ammonium acetate buffer solution to form a blue solution.</li>
			<li>Aluminum (III) is also precipitated in the presence of weak base to form the gelatinous-white Al(OH)3(s) compound. Addition of more base causes the compound to form the clear and colorless [Al(OH)4]-(aq) soluble complex.</li>
		</ol>
		</li>
		<li>Zinc ion
		<ol>
			<li>Add zinc (II) to a small amount of base to form a white precipitate. Then add more base to re-dissolve the precipitate and form the soluble [Zn(OH)4]2- complex.</li>
			<li>Add zinc (II) to potassium hexacyanoferrate, K4[Fe(CN)6] to form the light green precipitate K2Zn3[Fe(CN)6]2(s): 
			3 Zn2+(aq) + 2 K4[Fe(CN)6](aq) &#8594; K2Zn3[Fe(CN)6]2(s) + 6 K+(aq)&#160;</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>

The reactions shown here can be used to identify the presence of a class of cations or anions or be used very specifically for a certain ion. Because two reagents are used in the analyses, either reagent can be typically detected using the other. For example, instead of analyzing for the presence of chloride using silver ion, silver ion can be identified using chloride. A combination of common rules of precipitation followed by specific colorimetric or precipitation tests can be used to p...

determining the solubility rules of ionic compounds

Source: Laboratory of Dr. Neal Abrams &#8212; SUNY College of Environmental Science and Forestry
An ionic compound&#39;s solubility can be determined via qualitative analysis. Qualitative analysis is a branch of analytical chemistry that uses chemical properties and reactions to identify the cation or anion present in a chemical compound. While the chemical reactions rely on known solubility rules, those same rules can be determined by identifying the products that form. Qualitative analysis is not typically done in modern industrial chemistry labs, but it can be used easily in the field without the need of sophisticated instrumentation. Qualitative analysis also focuses on understanding ionic and net ionic reactions as well as organizing data into a flow chart to explain observations and make definitive conclusions.
Many cations have similar chemical properties, as do the anion counterparts. Correct identification requires careful separation and analysis to systematically identify the ions present in a solution. It is important to understand acid/base properties, ionic equilibria, redox reactions, and pH properties to identify ions successfully.
While there is a qualitative test for virtually every elemental and polyatomic ion, the identification process typically begins with knowing a &#34;class&#34; of ions being analyzed; cations or anions, elemental or polyatomic, groups or periods, transition or main group. In this experiment, both types of ions, cations and anions, are identified. The cations include polyatomic ions as well.

Source: Laboratory of Dr. Neal Abrams &#8212; SUNY College of Environmental Science and Forestry
An ionic compound&#39;s solubility can be determined via ...

Trends in the solubility properties of ionic compounds can be used for the qualitative analysis of ionic solutions. When a compound is added to a mixture of ionic solutions, many products can form, each with different solubility properties. If only one product is insoluble, then it alone will leave the solution. By performing sequential reactions, ions in a solution can be systematically identified and isolated.While a variety of analytical instruments exist for elemental analysis, the techniques are often time-consuming or require transporting samples between laboratories. Qualitative analytical techniques such as examining solubility properties are fast, accessible pre-screening methods for analysis.This video will introduce the solubility properties of ionic compounds, demonstrate procedures for selectively precipitating ionic compounds, and introduce a few applications of qualitative analysis using solubility trends in industrial settings.Ionic compounds are composed of a cation and an anion. When a reaction occurs between two different ionic compounds, the cation of one compound is electrostatically attracted to the anion of another, forming a new compound. The ions that do not participate in the reaction are called spectator ions, and are omitted from the net ionic reaction. When an ionic compound dissolves, they reversibly interact with solvent molecules, and the ions dissociate. If the interaction between an ion and the new counter-ion is stronger than between the ion and the solvent molecules, it will be more favorable for the product to be in the solid phase. The formation of solid product from solution is known as precipitation, and the solid is called the precipitate.Ions can be selectively isolated from solution by inducing reactions with insoluble precipitates. To design these reactions, cations and anions are assigned to broad categories based on solubility trends. Cations are grouped by identifying the anion common to their insoluble reaction products, and anions are likewise grouped by common cations. Solutions of these common ions are used to test for these groups.When separation is desired for ions belonging to the same group, specialized reagents or concentrated solutions can be used to induce selective reactions once the ions in that group have been isolated. These specialized reagents can also be used to confirm the identity of an isolated ion. Now that you understand the principles behind the qualitative analysis of ions, let's go through a technique for analyzing a solution for phosphate, followed by a procedure for separating a mixture of metal cations.To analyze a solution for phosphate, first prepare dilute test solutions of aqueous calcium, ammonium orthomolybdate, and concentrated nitric acid. Then, place 5 mL of the unknown solution in a test tube.Add the calcium solution dropwise to the unknown solution. The formation of a white precipitate could indicate the presence of calcium phosphate, or calcium carbonate. To verify the presence of phosphate, slowly add nitric acid to the test tube. Dissolution of the precipitate indicates that hydrogen phosphate has formed. The lack of gas bubbles indicates that no carbonate is present, as carbonate would have reacted with the acid to form carbon dioxide and water.Finally, slowly add the ammonium orthomolybdate to the test tube. Ammonium phosphomolybdate forms as a yellow precipitate, confirming the presence of phosphate in the solution.First, prepare dilute test solutions as listed in the text protocol. Obtain four test tubes and caps suitable for use in a centrifuge. Place a mixture of aqueous zinc, nickel, silver, and iron nitrates in one test tube. To begin separation, first slowly add dilute hydrochloric acid to the mixture, swirling gently. The white precipitate that forms is silver chloride. Continue adding chloride solution until no more precipitate forms.Separate the liquid, or supernatant, and the solid silver chloride by centrifugation. Decant the supernatant into the second test tube. Wash the silver chloride three times with water and decant each wash into the second test tube. Next, add the sodium hydroxide solution dropwise to the second test tube. Three precipitates will form: white zinc hydroxide, yellow iron hydroxide, and green nickel hydroxide. Continue adding sodium hydroxide until the solid white zinc compound dissolves, forming the soluble zincate ion. Separate the zinc solution and the solid nickel and iron compounds by centrifugation, and then decant the solution into the third test tube. Wash the solids with water three times and decant each into the zinc solution.Slowly add hydrochloric acid to the zinc solution in the third test tube until zinc hydroxide precipitates and then dissolves.Then, add potassium hexacyanoferrate dropwise to the zinc solution to form potassium zinc hexacyanoferrate as a white precipitate. Now, to the test tube containing solid nickel hydroxide and iron hydroxide, slowly add ammonia to form the soluble blue nickel hexammine ion. Separate the nickel solution from the solid iron hydroxide by centrifugation and decant the nickel solution into the fourth test tube. Wash the iron hydroxide three times with water and decant the washes into the nickel solution. Then, slowly add dimethylglyoxime to the nickel solution to form nickel dimethylglyoxime as a red precipitate. To the solid iron hydroxide, carefully add concentrated hydrochloric acid to form a solution of ferric chloride. To confirm the presence of iron, add thiocyanate to form the deep red thiocyanatoiron cation.The simplicity and speed of performing qualitative analysis of ions in solution makes this technique widely used in environmental chemistry and industry.When water contains a high concentration of metal cations such as calcium or magnesium, it is called hard water. These metal cations can react with anions in the water such as carbonate to form chalky deposits that clog pipes or hot water heaters. Water hardness can be assessed by adding a carbonate solution to a water sample. White precipitate indicates high levels of calcium.Phosphate is an important nutrient for many forms of life and is therefore used in both industrial and garden fertilizers, but an excess of phosphate can be detrimental, particularly in freshwater environments. Wastewater in residential and commercial areas can be tested for phosphates by adding nitric acid and ammonium orthomolybdate. Yellow precipitate indicates high levels of phosphates.You've just watched JoVE's introduction to solubility rules for ions. You should now be familiar with the principles of ionic reactions, a few procedures for qualitative analysis of solutions, and some applications of qualitative analysis using solubility.Thanks for watching!

Education

JoVE Science Education

General Chemistry

qualitative analysis for ion identification

Qualitative analysis can be used to identify the ions in an ionic compound and to infer solubility from the products that form. It is a branch of analytical chemistry that uses chemical properties and reactions to determine whether a cation or an anion is present. The same known solubility rules that guide these tests can also be learned by observing the reaction products.

This approach is not usually used in modern industrial chemistry labs, but it is practical in the field because it does not require sophisticated instruments. It also helps students practice ionic reactions and net ionic reactions. Results are organized in a flow chart so observations can be compared and used to reach clear conclusions.

Many cations have similar chemical properties, and many anions do as well. For that reason, the ions must be separated and analyzed carefully. Successful identification also depends on understanding acid-base behavior, ionic equilibria, redox reactions, and pH properties.

Qualitative tests exist for almost every elemental ion and polyatomic ion. The process usually starts by deciding which class of ions is being analyzed, such as cations or anions, elemental or polyatomic ions, and groups or periods. In this experiment, both cations and anions are identified, and the cations include polyatomic ions as well.

Qualitative Analysis for Ion Identification

qualitative-analysis-for-ion-identification

common lab glassware and uses

Choosing the Right Lab Glass Material

Lab glass materials affect durability, heating, and clarity in chemistry work. Glass is common in the laboratory because it is relatively low cost, extremely durable, and precise for many tasks. Some labware is now replaced by plastic or even everyday kitchen materials, but glass remains the standard material for laboratory work. Good lab technique also depends on best practices for using glassware. Not all glass used in labs is the same. Standard consumer-grade glass is called soda-lime...

solutions and concentrations

Preparing and Measuring Solution Concentration

Preparing and measuring solution concentration are key parts of chemistry. A solution is a homogeneous mixture. It contains solutes, which are present in small amounts, and a solvent, which is present in a large amount. This topic focuses on solid-liquid solutions. In these mixtures, one or more solid solutes dissolve in a liquid solvent. Solutions are used often in chemistry because they help store and handle small amounts of material, support chemical reactions, and make materials with...

determining the density of a solid and liquid

determining-the-density-of-a-solid-and-liquid

Measuring Density with Lab Glassware

Density is the mass of a substance divided by its volume. It is often written in units such as g/mL or kg/m3. Because density does not change with the amount of material present, it is an intensive property. To find density, both mass and volume must be measured. A balance is used to measure mass for both solids and liquids. The method for volume depends on the type of sample. Liquids take the shape of their container, so their volume can be measured with glassware such as a graduated...

determining the mass percent composition in an aqueous solution

determining-the-mass-percent-composition-in-an-aqueous-solution

Analyzing Solute Content in Water Solutions

Analyzing solute content in water solutions is an important analytical and forensic technique. In an aqueous solution, water is the solvent. The solvent is the main component. The dissolved minor component is the solute. The solute is dissolved in the solvent to make a solution. Water is the most common solvent in everyday life. It is also the main solvent in nearly all biological systems. In chemistry labs, the solvent may be another liquid, such as acetone, ether, or an alcohol. The solute...

determining the empirical formula

Empirical Formula by Gravimetric Analysis

Gravimetric analysis can be used to determine the empirical formula of a compound. The empirical formula gives the smallest whole-number ratio of elements in a molecular compound. In this experiment, that ratio is found for copper chloride hydrate, Cu x Cl y · nH2O. The method relies on the law of conservation of mass. Because mass is conserved, a reaction can be tracked by measuring changes in mass. This makes gravimetric analysis a simple and accurate way to help determine chemical formulas...

Qualitative analysis can be used to identify the ions in an ionic compound and to infer solubility from the products that form. It is a branch of analytical chemistry that uses chemical properties and reactions to determine whether a cation or an anion is present. The same known solubility rules that guide these tests can also be learned by observing the reaction products. This approach is not usually used in modern industrial chemistry labs, but it is practical in the field because it does...

using a ph meter

Measuring Acidic and Basic pH

Measuring acidic and basic pH helps describe how a solution behaves. Acids donate protons, or H+ ions, and bases donate hydroxide ions, or OH- ions. When acids and bases are mixed, they can neutralize each other. A neutral substance is neither acidic nor basic. pH is a practical way to compare proton concentration in solutions. The amount of H+ in most solutions is very small, so pH makes the value easier to use. pH was first defined from the reciprocal of proton concentration and was later...

introduction to titration

Acid-Base Titration of Vinegar

Acid-base titration is a common way to measure the concentration of an unknown solution. It is also called volumetric analysis because careful volume measurement is a key part of the method. In this technique, a standard solution is used to react with an analyte whose concentration is not known. Titrations can be grouped by the type of reaction they use. The most common examples are acid-base titrations and redox titrations. During a typical titration, the titrant is placed in a burette and...

ideal gas law

Gas Laws Behind Pressure, Volume, and Heat

Gas laws explain how pressure, volume, temperature, and the amount of gas are related. For most common gases near normal conditions, these relationships are a useful model. They also help connect what happens on the microscopic level with what we can measure in a lab, such as pressure and volume. The history of the ideal gas law began in the 17th century with a key pattern in air. Robert Boyle confirmed that pressure and volume are inversely proportional. This relationship is called Boyle’s...

spectrophotometric determination of an equilibrium constant

spectrophotometric-determination-of-an-equilibrium-constant

Measuring K with Beer’s Law and Color

The equilibrium constant, K, can be measured by tracking color in a chemical equilibrium. For a system with one colored species, spectrophotometry is used to relate absorbance to concentration. The colored component can then be measured directly, while the colorless components are found from the balanced chemical equation. This lab uses the Fe(SCN)2+ system to build a Beer’s law curve from experimental data. That curve is then applied to find the concentration of the colored ion in the...

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Chemical Equilibrium Shifts in a Color Test

Chemical equilibrium shifts are shown with a color test using iron(III) ions and thiocyanate ions. In this reversible reaction, Fe3+ and SCN- combine to form FeSCN2+. The changing color of the solution helps show which side of the equilibrium is favored. The experiment follows Le Châtelier's principle. This principle says that when temperature, pressure, or concentration changes disturb a system at equilibrium, the system responds by counteracting that change. Here, the focus is on...

freezing-point depression to determine an unknown compound

freezing-point-depression-to-determine-an-unknown-compound

Using Freezing Point to Identify an Unknown

Freezing-point depression can help identify an unknown compound. When a solid compound dissolves in a solvent, the freezing point of the solution becomes lower than the freezing point of the pure solvent. This change is linked to the molecular weight of the solute. In this experiment, the unknown compound is dissolved in cyclohexane. The freezing point of the cyclohexane solution is measured, and the freezing point of pure cyclohexane is measured as well. The difference between the two...

determining rate laws and the order of reaction

determining-rate-laws-and-the-order-of-reaction

Measuring Reaction Speed and Rate Law

Chemical reaction speed depends on the rate law and the reaction order. These ideas help describe how reactants change into products over time. The rate of a reaction can be affected by temperature, concentration, and the physical properties of the reactants. The rate law shows the role of each reactant in a reaction. It is written as a rate equation, where A and B are concentrations of different molecular species, m and n are reaction orders, and k is the rate constant. The reaction rate also...

using differential scanning calorimetry to measure changes in enthalpy

using-differential-scanning-calorimetry-to-measure-changes-in-enthalpy

Differential Scanning Calorimetry and Heat Flow

Differential scanning calorimetry, or DSC, is a thermodynamic analysis method that tracks heat flow as temperature changes. It compares a sample material sealed in a pan with an empty reference pan. Both pans are exposed to the same temperature conditions. The instrument records the energy difference needed to keep the two pans at the same temperature. This difference comes from the different heat capacities of the sample and the reference pan. As the temperature changes, the energy absorbed...

coordination chemistry complexes

Ligands and Color in Metal Complexes

Transition metals form coordination complexes with ligands in many everyday materials. These metals appear in vitamin supplements, electroplating baths, pigments in paints, and minerals. In many cases, they are found as cations because they readily oxidize, or lose electrons. Ligands are electron donors that surround the metal center. Their bond to the metal is called a coordinate-covalent bond. This bond is not purely ionic or covalent. It is dynamic, so ligands can exchange and re-coordinate...

general chemistry

This collection helps provide a solid foundation in general chemistry by showcasing basic lab techniques, demonstrating commonly used equipment, and exploring the theory behind fundamental methodology in Chemistry. 

Use qualitative analysis to identify cations and anions, organize ion tests in a flow chart, and connect observations to solubility rules.

Qualitative Analysis for Ion Identification | JoVE K12

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Physical Geology

Minerals

criteria-mineral-crystalline-solid-occurs-nature-inorganic-defined

Criteria of a mineral (crystalline solid, occurs in nature, inorganic, defined chemical composition)

Virginia  Standards of Learning

HIgh School

CH.5

CH.5.a

Arizona Science Standards

High School

Physical Science

HS+C.P1

HS+C.P1U1.5

Alabama Course of Study Science

Matter and Its Interactions

9-12.C.1.5.a

9-12.C.1.5.c

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Structure and Properties of Matter

HS-PS1-10.

HS. Chemical Reactions

HS-PS1-2.

HS-PS1-7.

Earth and Space Sciences

Earth’s Systems

HS-ESS2-2.

Neal Abrams

SUNY College of Environmental Science and Forestry

Overview

Principles of Qualitative Analysis of Ionic Solutions

Phosphate Analysis

Metal Cation Separation

Applications

Summary

Scientific Laws and Theories

Scientific Laws

In science, a law is defined as a concise, verbal or mathematical, statement that summarizes a vast number of experimental observations. ...

The Scientific Method

Chemistry is an empirical science. Scientists often pose questions to understand the chemistry in everyday life and seek answers to these questions. To ...

Classifying Matter by State

Chemistry is the study of matter and the changes it undergoes. Matter is anything that has mass and occupies space. Matter is all around us; the air, ...

Classifying Matter by Composition

Matter: Pure Substances and Mixtures
According to its composition, the matter can be classified into two broad categories &mdash; pure substances and ...

The Atomic Theory of Matter

The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter ...

Subatomic Particles

Dalton was only partially correct about the particles that make up matter. All matter is composed of atoms, and atoms are composed of three smaller ...

Elements: Chemical Symbols and Isotopes

A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is ...

Use models to explain how the scientific understanding of atomic structure has evolved.

PS.Chm.1.1

Radioactivity and Nuclear Equations

Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for ...

Types of Radioactivity

The most common types of radioactivity are &#945; decay, &#946; decay, &#947; decay, neutron emission, and electron capture.
Alpha (&#945;) decay is the ...

Nuclear Stability

Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10&#8722;15 meters, a nucleus is ...

Nuclear Binding Energy

The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect ...

Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. ...

Nuclear Fission

Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger ...

Nuclear Power

Controlled nuclear fission reactions are used to generate electricity. Any nuclear reactor that produces power via the fission of uranium or plutonium by ...

Nuclear Fusion

The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process ...

Nuclear Transmutation

Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with ...

Use models to compare nuclear reactions including alpha decay, beta decay and gamma decay; nuclear fusion and nuclear fission.

PS.Chm.1.2

Atomic Orbitals

An atomic orbital represents the three-dimensional regions in an atom where an electron has the highest probability to reside. The radial distribution ...

The Pauli Exclusion Principle

The arrangement of electrons in the orbitals of an atom is called its electron configuration. We describe an electron configuration with a symbol that ...

The Energies of Atomic Orbitals

In an atom, the negatively charged electrons are attracted to the positively charged nucleus. In a multielectron atom, electron-electron repulsions are ...

The Aufbau Principle and Hund's Rule

To determine the electron configuration for any particular atom, we can build the structures in the order of atomic numbers. Beginning with hydrogen, and ...

electron-configuration-of-multielectron-atoms

Electron Configuration of Multielectron Atoms

The alkali metal sodium (atomic number 11) has one more electron than the neon atom. This electron must go into the lowest-energy subshell available, the ...

Use models to explain how electrons are distributed in atoms.

PS.Chm.1.3

Periodic Classification of the Elements

The periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their ...

The Periodic Table

As early chemists discovered more elements, they realized that various elements could be grouped by their similar chemical behaviors. One such grouping ...

Atomic Mass

Atoms &mdash; and the protons, neutrons, and electrons that compose them &mdash; are extremely small. For example, a carbon atom weighs less than 2 ...

Molar Mass

The identity of a substance is defined not only by the types of atoms or ions it contains but by the quantity of each type of atom or ion. For example, ...

Use the Periodic Table as a model to predict the relative properties of elements based on the pattern of valence electrons in the outermost energy levels of atoms.

PS.Chm.2.1

atomic-radii-and-effective-nuclear-charge

Atomic Radii and Effective Nuclear Charge

The elements in groups of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number ...

Ionic Radii

Ionic radius is the measure used to describe the size of an ion. A cation always has fewer electrons and the same number of protons as the parent atom; it ...

Ionization Energy

The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy ...

Electron Affinity

The electron affinity (EA) is the energy change for adding an electron to a gaseous atom to form an anion (negative ion).



This process can be either ...

Construct an explanation to infer the atomic size, reactivity, electronegativity, and ionization energy of an element based on its position in the Periodic Table.

PS.Chm.2.2

Types of Chemical Bonds

Chemical bonding theories were pioneered by American chemist Gilbert&#xA0;N. Lewis. He developed a model called the Lewis model to explain the type and ...

Lewis Symbols and the Octet Rule

Chemical bonds are complex interactions between two or more atoms or ions, which reduce the potential energy of the molecule. Gilbert N. Lewis developed a ...

Ionic Bonding and Electron Transfer

Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence ...

The Born-Haber Cycle

Lattice Energy&#xA0;

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a ...

trends-in-lattice-energy-ion-size-and-charge

Trends in Lattice Energy: Ion Size and Charge

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a compound is a measure ...

Covalent Bonding and Lewis Structures

Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual ...

Electronegativity

Whether a bond is nonpolar or polar covalent is determined by a property of the bonding atoms called electronegativity.&#xA0;

Electronegativity values of ...

bond-polarity-dipole-moment-and-percent-ionic-character

Bond Polarity, Dipole Moment, and Percent Ionic Character

Bond Polarity

The absolute value of the difference in electronegativity (&Delta;EN) of two bonded atoms provides a rough measure of the polarity to be ...

lewis-structures-of-molecular-compounds-and-polyatomic-ions

Lewis Structures of Molecular Compounds and Polyatomic Ions

To draw Lewis structures for complicated molecules and molecular ions, it is helpful to follow a step-by-step procedure as outlined:


	Determine the ...

Analyze and interpret data to explain the mechanisms and properties of the two main types of intramolecular (ionic and covalent) bonds.

PS.Chm.3.1

Analyze the structure of atoms and isotopes.

Qualitative Analysis for Ion Identification

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