CHEM 121 Module 7

CHEM 121 Foundations of General Chemistry

electronic structure

the species involved, that is, the arrangement of the electrons around atoms, ions, or molecules

nuclear structure

the numbers of protons and neutrons within the nuclei of the atoms involved, remains unchanged during chemical reactions

nuclear chemistry 

the study of reactions that involve changes in nuclear structure

nucleus

the center of the atom

protons

which are positively charged

neutrons

which do not have a charge

electrons

orbit the nucleus and are negatively charged

electron cloud

the negatively charged region where electrons are located

atomic number (Z) of the element

the number of protons in the nucleus

sum of the mass number (A)

the number of protons and the number of neutrons

isotopes

atoms of the same element with the same atomic number but different mass numbers, due to differences in the number of neutrons

nuclide

referring to a single type of nucleus

X

the symbol for the element

A

the mass number

Z

the atomic number

nucleons

protons and neutrons, are packed together tightly in a nucleus

strong nuclear force

the force of attraction that holds the nucleus together.

force acts between protons, between neutrons, and between protons and neutrons.

electrostatic force

holds negatively charged electrons around a positively charged nucleus (the attraction between opposite charges)

mass defect of the atom

difference between the calculated and experimentally measured masses

nuclear binding energy

the energy produced when the atom’s nucleons are bound together; this is also the energy needed to break a nucleus into its constituent protons and neutrons

mass-energy equivalence equation

the conversion between mass and energy

E 

is energy

m 

is the mass of the matter being converted

 c

is the speed of light in a vacuum (2.9979 x 10⁸ m/s)

electron volts (eV)

1 eV equaling the amount of energy necessary to the move the charge of an electron across an electric potential difference of 1 volt, making 1 eV = 1.602 × 10^–19 J

band of stability

a region of stable nuclei within a plot of the number of neutrons versus the number of protons

radioactivity

unstable nuclei exhibit.

changing spontaneously (decaying) into other nuclei that are either in, or closer to, the band of stability.

unstable isotope (or radioisotope)

nuclear decay reactions convert one into another, more stable, isotope

nuclear reaction

occurs when changes in nuclei result in changes in their atomic numbers, mass numbers, or energy states

alpha particle

(High-energy) helium nuclei consisting of two protons and two neutrons

beta particle

(High-energy) electrons, and gamma rays are photons of very high-energy electromagnetic radiation

positron

particles with the same mass as an electron but with 1 unit of positive charge

proton

nuclei of hydrogen atoms

neutron

particles with a mass approximately equal to that of a proton but with no charge

gamma ray

very high-energy electromagnetic radiation

positrons

positively charged electrons (“anti-electrons”)

antimatter

particles with the same mass but the opposite state of another property (for example, charge) than ordinary matter

gamma rays (γ)

a type of high frequency electromagnetic energy (light waves) produced when antimatter encounters ordinary matter

nuclear reactions also follow conservation laws

the sum of the mass numbers of the reactants equals the sum of the mass numbers of the products.

the sum of the charges of the reactants equals the sum of the charges of the products.

radioactive decay

the spontaneous change of an unstable nuclide into another nuclide

parent nuclide

the unstable nuclide

daughter nuclide

the nuclide that results from the decay

alpha (α) decay

the spontaneous change of an unstable nuclide into another nuclide

beta (β) decay

the conversion of a neutron into a proton and a β particle (high-energy electron).

the β particle is emitted from the nucleus and is not an electron originating from the electron cloud

gamma emission (γ emission)

observed when a nuclide is formed in an excited state and then decays to its ground state with the emission of a γ ray, a quantum of high-energy electromagnetic radiation. The presence of a nucleus in an excited state is often indicated by an asterisk

positron emission (β⁺decay

the emission of a positron from the nucleus

electron capture

occurs when one of the inner electrons in an atom is captured by the atom’s nucleus

alpha decay

A: Decrease by 4.

Z: Decrease by 2.

beta eecay

A: Unchanged.

Z: Increase by 1.

gamma decay

A: Unchanged.

Z: Unchanged.

positron decay

A: Unchanged.

Z: Decrease by 1.

Electron Capture

A: Unchanged.

Z: Decrease by 1.

half-life (t_1/2)

the time required for half of the atoms in a sample to decay

nuclear transmutation

the conversion of one nuclide into another

transmutation reaction

the bombardment of one type of nuclei with other nuclei or with neutrons

particle accelerators

devices used to reach the kinetic energies necessary to produce transmutation reactions

fission

the breaking of a large nucleus into smaller pieces

chain reaction

provide more neutrons that can cause fission of even more nuclei, and so on

fissile or fissionable

material that can sustain a nuclear fission chain reaction

critical mass

the amount of a fissionable material that will support a self-sustaining chain reaction

subcritical mass

the amount of fissionable material that cannot sustain a chain reaction

supercritical mass

the amount of material in which there is an increasing rate of fission

radioactive tracer (or radioactive label)

replace one (or more) atom(s) with radioisotope(s) in a compound, we can track them by monitoring their radioactive emissions

Technetium-99

absorbed by damaged heart, lung, and liver tissues. Emits gamma rays, revealing specific locations of tissue damage

Thalium-201

becomes concentrated in healthy heart tissue, indicating healthy regions of the heart

Iodine-131

used to monitor Graves’ disease and conditions of the thyroid gland.

used to monitor brain and liver tumors.

Sodium-24

injected into the bloodstream to locate blockages to blood flow

radiation therapy

the use of high-energy radiation to damage the DNA of cancer cells, which kills them or keeps them from dividing

external beam radiation therapy

delivered by a machine outside the body

internal radiation therapy (brachytherapy)

from a radioactive substance that has been introduced into the body

nonionizing radiation

large difference in the magnitude of the biological effects

ionizing radiation

emissions energetic enough to knock electrons out of molecules

inorganic chemistry

the study of compounds that do not contain carbon-hydrogen bonds, called inorganic compounds

organic chemistry

the study of compounds that contain carbon-hydrogen bonds, called organic compounds

potentially 10⁶ different organic compounds

has four valence electrons; readily forms bonds.

carbon can form up to four covalent bonds with itself and other elements.

capable of forming complex structures such as chains, rings, and branches.

hydrocarbons

the simplest organic compounds, containing the elements hydrogen and carbon

alkanes

a type of hydrocarbon that contain only single covalent bonds between carbon atoms

saturated hydrocarbons

have the maximum number of H atoms for every C atom due to their single bonds

skeletal structure (also called a line-angle structure)

common method used by organic chemists to simplify the drawings of larger molecules

functional group

an atom or group of atoms attached to the main structure of a compound that determines the compound’s overall chemical properties

alkyl group

an alkane minus one hydrogen atom

substitution reaction

occurs when one or more of the alkane’s hydrogen atoms is replaced with a different atom or group of atoms

substituents

branches or functional groups that replace hydrogen atoms on a chain

unsaturated hydrocarboon

do not contain the greatest possible number of H atoms for each C atom in their structure due to the presence of a double bond

addition reactions

a double bond is broken to form two new single bonds

alkyne

a hydrocarbon molecule with one or more triple bonds

cycloalkanes

alkanes that have a ring structure

aromatic hydrocarbon

contains a benzene ring

alcohols

derivatives of hydrocarbons in which an –OH group has replaced a hydrogen atom