Chem. Final Vocabulary (Chs. 8 & 24)

Front 1

covalent bond

Back 1

a chemical bond that results from the sharing of valence electrons

Front 2

molecule

Back 2

forms when two or more atoms covalently bond and is lower in potential energy than its constituent atoms

Front 3

Lewis structure

Back 3

A model that uses electron-dot structures to show how electrons are arranged in molecules. Pairs of dots or lines represent bonding pairs.

Front 4

sigma bond

Back 4

a single covalent bond that is formed when an electron pair is shared by the direct overlap of bonding orbitals

Front 5

pi bond

Back 5

a bond that is formed when parallel orbitals overlap to share electrons

Front 6

endothermic reaction

Back 6

a chemical reaction or process in which a greater amount of energy is required to break the existing bonds in the reactants than is released when the new bonds form in the product molecules

Front 7

exothermic reaction

Back 7

a chemical reaction or process in which more energy is released than is required to break bonds in the initial reactants

Front 8

oxyacid

Back 8

any acid that contains hydrogen and an oxyanion

Front 9

structural formula

Back 9

a molecular model that uses symbols and bonds to show relative positions of atoms; can be predicted for many molecules by drawing the Lewis structure

Front 10

resonance

Back 10

condition that occurs when more than one valid Lewis structure exists for the same molecule

Front 11

coordinate covalent bond

Back 11

forms when one atom donates a pair of electrons to be shared with an atom or ion that needs two electrons to become stable

Front 12

VSEPR model

Back 12

Valence Shell Electron Pair Repulsion model, which is based on an arrangement that minimizes the repulsion of shared and unshared pairs of electrons around the central atom

Front 13

hybridization

Back 13

a process in which atomic orbitals are mixed to form new, identical hybrid orbitals

Front 14

polar covalent bond

Back 14

a type of bond that forms when electrons are not shared equally

Front 15

radioisotope

Back 15

isotopes of atoms that have unstable nuclei and emit radiation to attain more stable atomic configurations

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X ray

Back 16

a form of high-energy, penetrating electromagnetic radiation emitted from some materials that are in an excited electron state

Front 17

penetrating power

Back 17

the ability of radiation to pass through matter

Front 18

transmutation

Back 18

the conversion of an atom of one element to an atom of another element

Front 19

nucleon

Back 19

the positively charged protons and neutral neutrons contained in an atom’s nucleus

Front 20

strong nuclear force

Back 20

a force that acts on subatomic particles that are extremely close together

Front 21

band of stability

Back 21

the region on a graph within which all stable nuclei are found when plotting the number of neutrons versus the number of protons

Front 22

positron emission

Back 22

a radioactive decay process in which a proton in the nucleus is converted into a neutron and a positron, and then the positron is emitted from the nucleus

Front 23

positron

Back 23

a particle that has the same mass as an electron but an opposite charge

Front 24

electron capture

Back 24

a radioactive decay process that occurs when an atom’s nucleus draws in a surrounding electron, which combines with a proton to form a neutron, resulting in an X-ray photon being emitted

Front 25

radioactive decay series

Back 25

a series of nuclear reactions that starts with an unstable nucleus and results in the formation of a stable nucleus

Front 26

half-life

Back 26

the time required for one-half of a radioisotope’s nuclei to decay into its products

Front 27

radiochemical dating

Back 27

the process that is used to determine the age of an object by measuring the amount of a certain radioisotope remaining in that object

Front 28

induced transmutation

Back 28

the process in which nuclei are bombarded with high-velocity charged particles in order to create new elements

Front 29

transuranium element

Back 29

an element with an atomic number of 93 or greater in the periodic table

Front 30

mass defect

Back 30

the difference in mass between a nucleus and its component nucleons

Front 31

nuclear fission

Back 31

the splitting of a nucleus into smaller, more stable fragments, accompanied by a large release of energy

Front 32

critical mass

Back 32

the minimum mass of a sample of fissionable material necessary to sustain a nuclear chain reaction

Front 33

breeder reactor

Back 33

a nuclear reactor that is able to produce more fuel than it uses

Front 34

nuclear fusion

Back 34

the process of binding smaller atomic nuclei into a single, larger, and more stable nucleus

Front 35

thermonuclear reaction

Back 35

a nuclear fusion reaction

Front 36

ionizing radiation

Back 36

radiation that is energetic enough to ionize matter it collides with

Front 37

radiotracer

Back 37

an isotope that emits non-ionizing radiation and is used to signal the presence of an element or specific substance; can be used to analyze complex chemical reactions mechanisms and to diagnose disease