What Art of the Atom Allows One Atom to React With Another

Overview of Diminutive Structure

Atoms are made upwardly of particles called protons, neutrons, and electrons, which are responsible for the mass and accuse of atoms.

Learning Objectives

Discuss the electronic and structural backdrop of an atom

Key Takeaways

Key Points

• An atom is equanimous of 2 regions: the nucleus, which is in the middle of the atom and contains protons and neutrons, and the outer region of the atom, which holds its electrons in orbit around the nucleus.
• Protons and neutrons have approximately the same mass, well-nigh 1.67 × 10-24 grams, which scientists define every bit 1 atomic mass unit of measurement (amu) or one Dalton.
• Each electron has a negative accuse (-i) equal to the positive accuse of a proton (+one).
• Neutrons are uncharged particles found within the nucleus.

Primal Terms

• atom: The smallest possible amount of matter which yet retains its identity equally a chemical element, consisting of a nucleus surrounded by electrons.
• proton: Positively charged subatomic particle forming part of the nucleus of an atom and determining the diminutive number of an chemical element. Information technology weighs 1 amu.
• neutron: A subatomic particle forming part of the nucleus of an cantlet. It has no accuse. Information technology is equal in mass to a proton or it weighs ane amu.

An atom is the smallest unit of matter that retains all of the chemical properties of an element. Atoms combine to form molecules, which so interact to form solids, gases, or liquids. For instance, water is composed of hydrogen and oxygen atoms that take combined to course water molecules. Many biological processes are devoted to breaking down molecules into their component atoms so they can be reassembled into a more useful molecule.

Atomic Particles

Atoms consist of three bones particles: protons, electrons, and neutrons. The nucleus (center) of the atom contains the protons (positively charged) and the neutrons (no accuse). The outermost regions of the atom are called electron shells and comprise the electrons (negatively charged). Atoms have dissimilar backdrop based on the arrangement and number of their basic particles.

The hydrogen atom (H) contains but one proton, one electron, and no neutrons. This can exist determined using the diminutive number and the mass number of the element (see the concept on atomic numbers and mass numbers).

Construction of an atom: Elements, such every bit helium, depicted here, are made up of atoms. Atoms are made up of protons and neutrons located within the nucleus, with electrons in orbitals surrounding the nucleus.

Atomic Mass

Protons and neutrons take approximately the same mass, about 1.67 × 10^-24 grams. Scientists ascertain this corporeality of mass as i atomic mass unit (amu) or i Dalton. Although similar in mass, protons are positively charged, while neutrons have no charge. Therefore, the number of neutrons in an atom contributes significantly to its mass, but non to its charge.

Electrons are much smaller in mass than protons, weighing simply 9.11 × ten^-28 grams, or about 1/1800 of an atomic mass unit of measurement. Therefore, they do not contribute much to an chemical element's overall atomic mass. When considering atomic mass, it is customary to ignore the mass of whatever electrons and calculate the atom's mass based on the number of protons and neutrons lone.

Electrons contribute greatly to the atom'southward charge, as each electron has a negative charge equal to the positive accuse of a proton. Scientists define these charges every bit "+ane" and "-1. " In an uncharged, neutral cantlet, the number of electrons orbiting the nucleus is equal to the number of protons inside the nucleus. In these atoms, the positive and negative charges cancel each other out, leading to an atom with no net charge.

Protons, neutrons, and electrons: Both protons and neutrons have a mass of 1 amu and are plant in the nucleus. However, protons have a charge of +ane, and neutrons are uncharged. Electrons have a mass of approximately 0 amu, orbit the nucleus, and have a accuse of -1.

Exploring Electron Properties: Compare the behavior of electrons to that of other charged particles to discover properties of electrons such every bit charge and mass.

Book of Atoms

Accounting for the sizes of protons, neutrons, and electrons, most of the book of an atom—greater than 99 percent—is, in fact, empty space. Despite all this empty space, solid objects practise not just laissez passer through one some other. The electrons that surround all atoms are negatively charged and crusade atoms to repel one another, preventing atoms from occupying the aforementioned space. These intermolecular forces prevent you from falling through an object similar your chair.

Interactive: Build an Atom: Build an atom out of protons, neutrons, and electrons, and see how the element, charge, and mass change. Then play a game to exam your ideas!

Atomic Number and Mass Number

The atomic number is the number of protons in an element, while the mass number is the number of protons plus the number of neutrons.

Learning Objectives

Determine the relationship between the mass number of an atom, its atomic number, its diminutive mass, and its number of subatomic particles

Primal Takeaways

Key Points

• Neutral atoms of each chemical element contain an equal number of protons and electrons.
• The number of protons determines an element's atomic number and is used to distinguish one element from some other.
• The number of neutrons is variable, resulting in isotopes, which are different forms of the same atom that vary only in the number of neutrons they possess.
• Together, the number of protons and the number of neutrons determine an element'due south mass number.
• Since an chemical element'due south isotopes have slightly different mass numbers, the atomic mass is calculated by obtaining the mean of the mass numbers for its isotopes.

Fundamental Terms

• mass number: The sum of the number of protons and the number of neutrons in an cantlet.
• diminutive number: The number of protons in an atom.
• atomic mass: The average mass of an cantlet, taking into business relationship all its naturally occurring isotopes.

Diminutive Number

Neutral atoms of an element incorporate an equal number of protons and electrons. The number of protons determines an element'southward atomic number (Z) and distinguishes one element from another. For example, carbon's atomic number (Z) is half dozen because it has six protons. The number of neutrons tin vary to produce isotopes, which are atoms of the aforementioned element that have dissimilar numbers of neutrons. The number of electrons can as well exist different in atoms of the same element, thus producing ions (charged atoms). For example, iron, Iron, can be in its neutral state, or in the +2 and +three  ionic states.

Mass Number

An element'south mass number (A) is the sum of the number of protons and the number of neutrons. The pocket-size contribution of mass from electrons is disregarded in calculating the mass number. This approximation of mass can exist used to easily calculate how many neutrons an element has by only subtracting the number of protons from the mass number. Protons and neutrons both counterbalance about one atomic mass unit of measurement or amu. Isotopes of the same element volition accept the aforementioned atomic number but different mass numbers.

Atomic number, chemic symbol, and mass number: Carbon has an atomic number of half-dozen, and two stable isotopes with mass numbers of twelve and thirteen, respectively. Its average diminutive mass is 12.11.

Scientists determine the atomic mass by calculating the mean of the mass numbers for its naturally-occurring isotopes. Often, the resulting number contains a decimal. For example, the atomic mass of chlorine (Cl) is 35.45 amu because chlorine is equanimous of several isotopes, some (the majority) with an diminutive mass of 35 amu (17 protons and 18 neutrons) and some with an diminutive mass of 37 amu (17 protons and 20 neutrons).

Given an atomic number (Z) and mass number (A), y'all tin can discover the number of protons, neutrons, and electrons in a neutral cantlet. For instance, a lithium atom (Z=3, A=vii amu) contains three protons (found from Z), iii electrons (as the number of protons is equal to the number of electrons in an atom), and four neutrons (7 – 3 = iv).

Isotopes

Isotopes are various forms of an chemical element that have the same number of protons, but a unlike number of neutrons.

Learning Objectives

Discuss the properties of isotopes and their use in radiometric dating

Key Takeaways

Key Points

• Isotopes are atoms of the same element that contain an identical number of protons, but a dissimilar number of neutrons.
• Despite having different numbers of neutrons, isotopes of the same element accept very similar physical backdrop.
• Some isotopes are unstable and volition undergo radioactive decay to go other elements.
• The predictable half-life of dissimilar decomposable isotopes allows scientists to date textile based on its isotopic composition, such as with Carbon-14 dating.

Central Terms

• isotope: Any of two or more forms of an element where the atoms have the same number of protons, but a different number of neutrons within their nuclei.
• half-life: The time it takes for half of the original concentration of an isotope to decay back to its more stable form.
• radioactive isotopes: an atom with an unstable nucleus, characterized past excess energy bachelor that undergoes radioactive decay and creates most usually gamma rays, blastoff or beta particles.
• radiocarbon dating: Determining the age of an object by comparing the ratio of the 14C concentration found in it to the corporeality of 14C in the atmosphere.

What is an Isotope?

Isotopes are diverse forms of an element that have the same number of protons but a dissimilar number of neutrons. Some elements, such equally carbon, potassium, and uranium, have multiple naturally-occurring isotopes. Isotopes are divers first by their element and then past the sum of the protons and neutrons present.

• Carbon-12 (or ¹²C) contains six protons, vi neutrons, and six electrons; therefore, information technology has a mass number of 12 amu (six protons and six neutrons).
• Carbon-14 (or ¹⁴C) contains six protons, 8 neutrons, and vi electrons; its atomic mass is 14 amu (6 protons and 8 neutrons).

While the mass of individual isotopes is different, their physical and chemic properties remain mostly unchanged.

Isotopes do differ in their stability. Carbon-12 (¹²C) is the most abundant of the carbon isotopes, accounting for 98.89% of carbon on Earth. Carbon-14 (¹⁴C) is unstable and only occurs in trace amounts. Unstable isotopes most commonly emit alpha particles (Heⁱⁱ⁺) and electrons. Neutrons, protons, and positrons tin can besides be emitted and electrons tin can be captured to attain a more stable diminutive configuration (lower level of potential energy ) through a process called radioactive decay. The new atoms created may be in a loftier free energy state and emit gamma rays which lowers the energy but alone does not alter the atom into another isotope. These atoms are called radioactive isotopes or radioisotopes.

Radiocarbon Dating

Carbon is normally present in the atmosphere in the form of gaseous compounds like carbon dioxide and methyl hydride. Carbon-14 (¹⁴C) is a naturally-occurring radioisotope that is created from atmospheric ^xivN (nitrogen) by the addition of a neutron and the loss of a proton, which is caused past cosmic rays. This is a continuous process and then more ^fourteenC is always existence created in the atmosphere. Once produced, the ¹⁴C often combines with the oxygen in the atmosphere to grade carbon dioxide. Carbon dioxide produced in this way diffuses in the atmosphere, is dissolved in the sea, and is incorporated past plants via photosynthesis. Animals consume the plants and, ultimately, the radiocarbon is distributed throughout the biosphere.

In living organisms, the relative amount of ¹⁴C in their torso is approximately equal to the concentration of ^fourteenC in the atmosphere. When an organism dies, it is no longer ingesting ¹⁴C, so the ratio between ^xivC and ¹²C will decline as ^xivC gradually decays back to ^fourteenN. This boring process, which is called beta decay, releases free energy through the emission of electrons from the nucleus or positrons.

After approximately 5,730 years, half of the starting concentration of ¹⁴C will accept been converted back to ^fourteenN. This is referred to as its half-life, or the time information technology takes for half of the original concentration of an isotope to decay back to its more stable grade. Because the half-life of ¹⁴C is long, it is used to date formerly-living objects such as former bones or wood. Comparing the ratio of the ^xivC concentration institute in an object to the amount of ¹⁴C in the temper, the amount of the isotope that has not yet decayed can exist adamant. On the basis of this amount, the age of the textile can exist accurately calculated, as long every bit the material is believed to be less than 50,000 years old. This technique is chosen radiocarbon dating, or carbon dating for brusk.

Application of carbon dating: The age of carbon-containing remains less than 50,000 years old, such as this pygmy mammoth, can exist determined using carbon dating.

Other elements accept isotopes with unlike half lives. For example, ^fortyK (potassium-40) has a half-life of 1.25 billion years, and ²³⁵U (uranium-235) has a half-life of about 700 million years. Scientists often use these other radioactive elements to date objects that are older than 50,000 years (the limit of carbon dating). Through the use of radiometric dating, scientists can study the historic period of fossils or other remains of extinct organisms.

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Source: https://courses.lumenlearning.com/boundless-chemistry/chapter/the-structure-of-the-atom/

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