Name: atomic identity, mass, and isotopes
Uploaded: 2023-06-23T15:38:43.000Z
Duration: 1 min 12 s
Channel: JoVE

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Matter and Its Interactions

HS-PS1-2

Atomic Number and Mass Number

Le numéro atomique, noté Z, est le nombre total de protons dans le noyau d’un atome.
Sur le tableau périodique, chaque carré représente un élément ayant un numéro atomique unique. Ces éléments sont classés par ordre croissant de numéro atomique.
Un atome avec un proton est de l’hydrogène, un atome avec deux protons est de l’hélium, et ainsi de suite.
Le nombre de masse d’un atome est la somme des protons et des neutrons dans le noyau atomique, représentés par la lettre A.
Ainsi, un atome d’hydrogène avec un proton et aucun neutron a un nombre de masse de un, tandis qu’un atome d’hélium avec deux protons et deux neutrons a un nombre de masse de quatre.
Les éléments peuvent avoir plusieurs isotopes avec le même nombre de protons mais un nombre différent de neutrons.
Par exemple, les atomes de carbone existent sous forme de carbone 12 avec six protons et six neutrons, de carbone 13 avec six protons et sept neutrons, ou de carbone 14 avec six protons et huit neutrons.

numéro atomique et numéro de masse

Le nombre de protons dans le noyau d'un atome est son numéro atomique (Z). C'est la caractéristique définissante d'un élément. Sa valeur détermine l'identité de l'atome. Par exemple, n'importe quel atome qui contient six protons est l'élément carbone et a le numéro atomique 6, peu importe le nombre de neutrons ou d'électrons qu'il peut avoir. Un atome neutre doit contenir le même nombre de charges positives et négatives, donc le nombre de protons est égal au nombre d'électrons. Cela signifie que le numéro atomique indique également le nombre d'électrons dans un atome. 

 Numéro de masse 

 Le nombre total de protons et de neutrons dans un atome s'appelle son numéro de masse (A). Le nombre de neutrons est la différence entre le numéro de masse et le numéro atomique: (A - Z). Dans leur forme la plus courante, de nombreux éléments contiennent le même nombre de neutrons que de protons. Par exemple, la forme la plus courante du carbone a six neutrons et six protons. 

 Isotopes 

 Au début des années 1900, le chimiste anglais Frederick Soddy a réalisé qu'un élément pouvait avoir des types d'atomes avec des masses différentes qui étaient chimiquement indistinguables. Ces différents types sont appelés isotopes - des atomes du même élément qui diffèrent par leur masse. Les isotopes diffèrent en masse car ils ont des nombres de neutrons différents mais sont chimiquement identiques car ils ont le même nombre de protons. Soddy a reçu le prix Nobel de chimie en 1921 pour cette découverte. 

 Ce texte est adapté de
 <a href="https://openstax.org/books/chemistry-2e/pages/2-3-atomic-structure-and-symbolism?query=atomic%20number&target=%7B%22type%22%3A%22search%22%2C%22index%22%3A0%7D#fs-idp27048016">Openstax, Chemistry 2e, Section 2.3: Atomic Structure and Symbolism</a>,
 <a href="https://openstax.org/books/chemistry-2e/pages/2-2-evolution-of-atomic-theory?query=isotopes&target=%7B%22type%22%3A%22search%22%2C%22index%22%3A0%7D#fs-idp40043728">Section:2.2: Evolution of Atomic theory and </a>
 <a href="https://openstax.org/books/anatomy-and-physiology-2e/pages/2-1-elements-and-atoms-the-building-blocks-of-matter">Anatomy and Physiology 2e, Section 2.1: Elements and Atoms: the building blocks of matter</a>
 <a href="https://openstax.org/books/chemistry-2e/pages/2-2-evolution-of-atomic-theory?query=isotopes&target=%7B%22type%22%3A%22search%22%2C%22index%22%3A0%7D#fs-idp40043728">.</a>

Numéro atomique et numéro de masse

Le nombre de protons dans le noyau d’un atome est son numéro atomique (Z). C’est la caractéristique déterminante d’un élément. Sa valeur détermine l’identité de ...

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Anatomy and Physiology

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Unit 1

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Fundamentals of Chemistry

Les fondamentaux de la chimie

KEY TERMS AND CONCEPTS

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atomic identity, mass, and isotopes

Atomic identity depends on the number of protons in the nucleus, and mass depends on protons and neutrons together. The number of protons is the atomic number, or Z. It defines the element. For example, any atom with six protons is carbon, no matter how many neutrons or electrons it has.

In a neutral atom, the number of protons equals the number of electrons. Because of that, the atomic number also tells you the number of electrons in the atom. The total number of protons and neutrons is called the mass number, or A. The number of neutrons can be found by subtracting the atomic number from the mass number, or A minus Z.

Many elements have a common form with the same number of neutrons as protons. Carbon is one example. Its most common form has six protons and six neutrons. Some atoms of the same element can still differ in mass. These are called isotopes. Isotopes have the same number of protons, but different numbers of neutrons, so they are chemically identical even though their masses are different. In the early 1900s, Frederick Soddy identified isotopes and later received the 1921 Nobel Prize in Chemistry for the discovery.

Atomic Identity, Mass, and Isotopes

what is matter?

Matter, Mass, and Weight Basics

Matter is the substance that makes up the universe, from a grain of sand to a star. Scientists define matter as anything that occupies space and has mass. Mass is the amount of matter in an object, while weight depends on gravity. Mass stays the same whether an object is on Earth or in the zero-gravity environment of outer space. Weight changes when gravity changes. An object weighs more where gravity is stronger and less where gravity is weaker. A piece of cheese that weighs a pound on Earth...

the periodic table and organismal elements

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Organismal Elements in the Periodic Table

The periodic table helps identify the elements that make up living organisms. Biology groups these as organismal elements because they are the chemical building blocks of life. These elements are found in different amounts in the body. Some are present in large quantities, while others are needed only in small amounts. The video connects the periodic table to the elements that organisms actually use. Understanding organismal elements helps students link chemistry to biology. It shows how...

atomic structure

From Atomos to the Modern Atom

Atoms are the tiny building blocks of matter, and ideas about them go back to the Greek philosopher Democritus. He suggested that everything on Earth is made of atomos, a Greek word meaning "indivisible." That idea later led to the modern word atom. In the 19th century, John Dalton developed an atomic theory that is still largely correct today. He proposed five key ideas. All matter is made of tiny particles called atoms. Atoms of the same element are alike, and atoms of different elements are...

chemical symbols

Chemical Symbols and Element Names

Chemical symbols are short abbreviations that stand for an element or a single atom of that element. Mercury, for example, has the symbol Hg. The same symbol can point to one atom of mercury in the microscopic domain or to a sample labeled as many atoms of mercury in the macroscopic domain. Many symbols come from the element’s common name. Others are shortened from a name in another language. Most chemical symbols use one or two letters. For a few elements with atomic numbers above 112,...

atomic number and mass number

Atomic identity depends on the number of protons in the nucleus, and mass depends on protons and neutrons together. The number of protons is the atomic number, or Z. It defines the element. For example, any atom with six protons is carbon, no matter how many neutrons or electrons it has. In a neutral atom, the number of protons equals the number of electrons. Because of that, the atomic number also tells you the number of electrons in the atom. The total number of protons and neutrons is...

atomic weight

Atomic Mass and Mole Calculations

Atomic mass and mole calculations help explain how much matter is in atoms and compounds. Protons and neutrons have about the same mass, about 1.67 × 10 -24 grams. Scientists define that mass as one atomic mass unit, or amu, also called one Dalton. Electrons are much lighter than protons. They weigh only 9.11 × 10 -28 grams, or about 1/1800 of an atomic mass unit. Because of that small mass, electrons do not add much to an element’s overall atomic mass. When chemists calculate atomic mass,...

isotopes and radioisotopes

Radioisotopes in Medicine and Imaging

Radioisotopes are unstable isotopes that can be used to study the body and treat disease. An isotope is an atom of the same element that has a different mass because it contains a different number of neutrons. It still has the same number of protons, so it remains chemically identical. English chemist Frederick Soddy explained this idea in the early 1900s and later received the Nobel Prize in Chemistry in 1921. Some isotopes have more neutrons than usual and are called heavy isotopes. These...

electron behavior

Electron Shells and Discovery

Electrons are negatively charged subatomic particles that stay near the positively charged nucleus of an atom. They occupy spaces linked to energy levels called shells. They are also arranged into subshells and orbitals within each shell. An electron’s shell shows its general energy level. Electrons closer to the nucleus have less energy, while electrons farther away have more energy. The outer shells have more space, so they can hold more electrons than the inner shells. Subshells describe...

introduction to chemical bonds

How Atoms Bond to Reach Stability

Atoms bond to become more stable, and their outermost electrons play the biggest role in that process. The inner electron shell can hold two electrons. The next two shells can each hold eight electrons. This is called the octet rule. It states that, except for the innermost shell, atoms are most stable when their valence shell, or outer shell, has eight electrons. When atoms do not have enough electrons to fill that outer shell, they form chemical bonds with other atoms. A chemical bond is the...

ionic bonds

Ionic Bonds and Charge Transfer

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covalent bonds

Polar and Nonpolar Covalent Bonds

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hydrogen bonds

Hydrogen Bonding and DNA Stability

Hydrogen bonding helps explain why some molecules stick together more strongly than others. A hydrogen bond forms when a weakly positive hydrogen atom, already bonded to an electronegative atom, is attracted to another electronegative atom on a nearby polar molecule. Common examples include water, hydrogen fluoride, and ammonia. This attraction happens because hydrogen has a much lower electronegativity than atoms such as fluorine, oxygen, and nitrogen. The electronegativity difference, along...

ions, molecules, and compounds

Atomic Charges, Bonds, and Compounds

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states of matter

Solids, Liquids, Gases, and Plasma

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colloids and suspensions

Suspensions, Sedimentation, and Colloids

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introduction to chemical reactions

Chemical Reaction Basics and Equilibrium

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Electron Transfer and Chemical Equilibrium

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factors influencing the rate of chemical reactions

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Chemical Reaction Rates and Catalysts

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acids, bases and neutralization reactions

How pH Affects Cells and Digestion

Acids, bases, and pH help control how cells and body systems work. In biology, pH can strongly affect enzymes, proteins, and nucleic acids. Enzymes work best within a certain pH range, and pH changes can alter their structure or denature them, which changes how they function. Acids release hydrogen ions, or H+, in solution. A hydrogen ion is a proton, so it is very reactive in chemical reactions. Strong acids release all of their H+ in water and ionize completely. Hydrochloric acid (HCl) is a...

key terms and concepts

Learn how protons define an element, how to find mass number and neutrons, and why isotopes of the same element have different masses.

Atomic Identity, Mass, and Isotopes | JoVE K12

anatomy and physiology

JoVE Core Anatomy and Physiology showcases the anatomical and physiological details of the human body in comprehensive, clear, and engaging video animations. This collection of lessons focuses on the structures, components, functions, and requirements of the human body. It is complemented by scientist-in-action videos that demonstrate the application of this knowledge in real-world medical and research settings.

Earth and Space Science

Earth’s Place in the Universe

HS-ESS1-3

Florida Department of Education

SC.912.P.8

SC.912.P.8.4

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South Carolina College and Career Ready Science Standards

Chemistry

C-PS1-1

Georgia Standards of Excellence

9-12

SPS1.

Properties of Atoms, Ions, and Isotopes

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 ...

Atomic Structure

All matter is composed of atoms, the smallest individual units of elements. Each atom is made up of three subatomic particles: protons, neutrons, and ...

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 ...

Electronic Structure of Atoms


An atom comprises protons and neutrons, which are contained inside the dense, central&#160;core called the nucleus, with electrons present around the ...

Electron Behavior

Electrons are negatively charged subatomic particles that are attracted to an orbit around the positively-charged nucleus of an atom. They reside in ...

Electron Orbital Model

Orbitals are the areas outside of the atomic nucleus where electrons are most likely to reside. They are characterized by different energy levels, shapes, ...

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 Configurations

Electron configurations and orbital diagrams can be determined by applying the Aufbau principle (each added electron occupies the subshell of lowest ...

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 ...

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 ...

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 ...

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 ...

Alkali Metals

Group 1 elements are soft and shiny metallic solids. They are malleable, ductile, and good conductors of heat and electricity. The melting points of the ...

Halogens

Group 17 elements, known as halogens, are nonmetals. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine a solid. ...

Noble Gases


The elements in group 18 are noble gases (helium, neon, argon, krypton, xenon, and radon). They earned the name &ldquo;noble&rdquo; because they were ...

Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms. [Clarification Statement: Examples of properties that could be predicted from patterns could include reactivity of metals, types of bonds formed, numbers of bonds formed, and reactions with oxygen.] [Assessment Boundary: Assessment is limited to main group elements. Assessment does not include quantitative understanding of ionization energy beyond relative trends.]

HS-PS1-1

The number of protons in the nucleus of an atom is its atomic number (Z). This is the defining trait of an element. Its value determines the identity of ...

Chemical Reactions

A chemical reaction is a process by which the bonds in the atoms of substances are rearranged to generate new substances. Matter cannot be created or ...

Chemical Equations

Chemical equations represent the identities and relative quantities of substances involved in a chemical reaction. The substances undergoing reaction are ...

physical-and-chemical-properties-of-matter

Physical and Chemical Properties of Matter

The characteristics that enable us to distinguish one substance from another are called properties.

Physical Properties of Matter

A physical property is ...

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 ...

Predicting Reaction Outcomes

Kinetics describes the rate and path by which a reaction occurs. In contrast, thermodynamics deals with state functions and describes the properties, ...

Chemical Reactions in Aqueous Solutions

Chemical substances interact in many different ways. Certain chemical reactions exhibit common patterns of reactivity. Due to the vast number of chemical ...

Multi-Step Reactions

Chemical reactions often occur in a stepwise fashion involving two or more distinct reactions taking place in a sequence. A balanced equation indicates ...

Reaction Mechanisms

Chemical reactions often occur in a stepwise fashion, involving two or more distinct reactions taking place in a sequence. A balanced equation indicates ...

Rate-Determining Steps

Relating Reaction Mechanisms
In a multistep reaction mechanism, one of the elementary steps progresses significantly slower than the others. This slowest ...

Reaction Stoichiometry

A balanced chemical equation provides a great deal of information in a very succinct format. Chemical formulas provide the identities of the reactants and ...

Limiting Reactant

The relative amounts of reactants and products represented in a balanced chemical equation are often referred to as stoichiometric amounts. However, in ...

Reaction Yield

The theoretical yield of a reaction is the amount of product estimated to form based on the stoichiometry of the balanced chemical equation. The ...

stoichiometry-product-yield-and-limiting-reactants

Stoichiometry, Product Yield, and Limiting Reactants

Chemical equations represent how a chemical reaction proceeds from reactants to products through physical or chemical change using chemical formulas.
...

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Preparation of 25% v/v Ethylenediamine in Deionized WaterExpand
	Here, we show the laboratory ...

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Synthesis of tris(ethylenediamine)nickel chlorideExpand
	In this lab, you will combine nickel ...

Balancing Redox Equations

Electrochemistry is the science involved in the interconversion of electrical and chemical reactions. Such reactions are called reduction-oxidation, or ...

Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties. [Clarification Steatement: Examples of chemical reactions could include the reaction of sodium and chlorine, of carbon and oxygen, or of carbon and hydrogen.] [Assessment Boundary: Assessment is limited to chemical reactions involving main group elements and combustion reactions.]

What is Matter?

The substance of the universe&#8212;from a grain of sand to a star&#8212;is called matter. Scientists define matter as anything that occupies space and ...

Plan and conduct an investigation to gather evidence to compare the structure of substances at the bulk scale to infer the strength of electrical forces between particles. [Clarification Statement: Emphasis is on understanding the strengths of forces between particles, not on naming specific intermolecular forces (such as dipole-dipole). Examples of particles could include ions, atoms, molecules, and networked materials (such as graphite). Examples of bulk properties of substances could include the melting point and boiling point, vapor pressure, and surface tension.] [Assessment Boundary: Assessment does not include Raoult’s law calculations of vapor pressure.]

HS-PS1-3

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 ...

Bond Energies and Bond Lengths

Stable molecules exist because covalent bonds hold the atoms together. The strength of a covalent bond is measured by the energy required to break it, ...

Develop a model to illustrate that the release or absorption of energy from a chemical reaction system depends upon the changes in total bond energy. [Clarification Statement: Emphasis is on the idea that a chemical reaction is a system that affects the energy change. Examples of models could include molecular-level drawings and diagrams of reactions, graphs showing the relative energies of reactants and products, and representations showing energy is conserved.] [Assessment Boundary: Assessment does not include calculating the total bond energy changes during a chemical reaction from the bond energies of reactants and products.]

HS-PS1-4

Atomic Identity, Mass, and Isotopes

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