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

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Atomic Number and Mass Number

El número atómico, denotado como Z, es el número total de protones en el núcleo de un átomo.
En la tabla periódica, cada cuadrado representa un elemento que tiene un número atómico único. Estos elementos están dispuestos en orden creciente de número atómico.
Un átomo con un protón es hidrógeno, un átomo con dos protones es helio, y así sucesivamente.
El número de masa de un átomo es la suma de los protones y neutrones en el núcleo atómico, representada por la letra A.
Entonces, un átomo de hidrógeno con un protón y sin neutrones tiene un número de masa de uno, mientras que un átomo de helio con dos protones y dos neutrones tiene un número de masa de cuatro.
Los elementos pueden tener múltiples isótopos con el mismo número de protones pero diferente número de neutrones.
Por ejemplo, los átomos de carbono existen como carbono-12 con seis protones y seis neutrones, carbono-13 con seis protones y siete neutrones, o carbono-14 con seis protones y ocho neutrones.

número atómico y número de masa

El número de protones en el núcleo de un átomo es su número atómico (Z). Esta es la característica definitoria de un elemento. Su valor determina la identidad del átomo. Por ejemplo, cualquier átomo que contenga seis protones es el elemento carbono y tiene un número atómico de 6, independientemente de cuántos neutrones o electrones pueda tener. Un átomo neutro debe contener el mismo número de cargas positivas y negativas, por lo que el número de protones es igual al número de electrones. Esto significa que el número atómico también indica el número de electrones en un átomo.

Número de masa

El número total de protones y neutrones en un átomo se llama número de masa (A). El número de neutrones es la diferencia entre el número de masa y el número atómico: (A - Z). En su forma más común, muchos elementos contienen el mismo número de neutrones que protones. Por ejemplo, la forma más común de carbono tiene seis neutrones y seis protones.

Isótopos

A principios del siglo XX, el químico inglés Frederick Soddy se dio cuenta de que un elemento podría tener tipos de átomos con diferentes masas que eran químicamente indistinguibles. Estos diferentes tipos se llaman isótopos: átomos del mismo elemento que difieren en masa. Los isótopos difieren en masa porque tienen diferentes números de neutrones, pero son químicamente idénticos porque tienen el mismo número de protones. Soddy recibió el Premio Nobel de Química en 1921 por este descubrimiento.

Este texto está adaptado 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>

Número atómico y número de masa

El número de protones en el núcleo de un átomo es su número atómico (Z). Este es el rasgo definitorio de un elemento. Su valor determina la identidad de ...

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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

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Matter, Mass, and Weight Basics

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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

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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

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isotopes and radioisotopes

Radioisotopes in Medicine and Imaging

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ionic bonds

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covalent bonds

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hydrogen bonds

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ions, molecules, and compounds

Atomic Charges, Bonds, and Compounds

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colloids and suspensions

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acids, bases and neutralization reactions

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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

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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 ...

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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

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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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