Unit 1: Chemistry of life

Question 1

Anion

Answer 1

A negatively charged atom

Question 2

Atom

Answer 2

The smallest unit of matter that retains the properties of an element.

Question 3

Atomic mass

Answer 3

The mass of one atom

Question 4

Atomic nucleus

Answer 4

An atom’s dense central core, containing protons and neutrons.

Question 4

Atomic number

Answer 4

The number of protons in the nucleus of an atom, unique for each element and designated by a subscript.

Question 5

Cation

Answer 5

A positively charged atom

Question 6

Chemical bond

Answer 6

An attraction between two atoms, resulting from a sharing of outer-shell electrons or the presence of opposite charges on the atoms.

Question 7

Chemical equilibrium

Answer 7

In a chemical reaction, the state in which the rate of the forward reaction equals the rate of the reverse reaction, so that the relative concentrations of the reactants and products do not change with time.

Question 8

Chemical reaction

Answer 8

The making and breaking of chemical bonds, leading to changes in the composition of matter.

Question 9

Compound

Answer 9

A substance consisting of two or more different elements combined in a fixed ratio.

Question 10

Covalent bond

Answer 10

A type of strong chemical bond in which two atoms share one or more pairs of valence electrons.

Question 11

Dalton

Answer 11

A measure of mass for atoms and subatomic particles; the same as the atomic mass unit, or amu.

Question 12

Double bond

Answer 12

A double covalent bond; the sharing of two pairs of valence electrons by two atoms.

Question 13

Electron

Answer 13

A subatomic particle with a single negative electrical charge and a mass about 1/2,000 that of a neutron or proton.

Question 14

Electronegativity

Answer 14

The attraction of a given atom for the electrons of a covalent bond.

Question 15

Electron shell

Answer 15

An energy level of electrons at a characteristic average distance from the nucleus of an atom.

Question 16

Electron

Answer 16

Any substance that cannot be broken down to any other substance by chemical reactions.

Question 17

Energy

Answer 17

The capacity to cause change, especially to do work (to move matter against an opposing force).

Question 18

Essential element

Answer 18

A chemical element required for an organism to survive, grow, and reproduce.

Question 19

Half-life

Answer 19

The amount of time it takes for 50% of a sample of a radioactive isotope to decay.

Question 20

Hydrogen bond

Answer 20

A type of weak chemical bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule or in another region of the same molecule.

Question 21

Ion

Answer 21

An atom or group of atoms that has gained or lost one or more electrons, thus acquiring a charge.

Question 22

Ionic bond

Answer 22

A chemical bond resulting from the attraction between oppositely charged ions.

Question 23

Ionic compound

Answer 23

A compound resulting from the formation of an ionic bond; also called a salt.

Question 24

Isotope

Answer 24

One of several atomic forms of an element, each with the same number of protons but a different number of neutrons, thus differing in atomic mass.

Question 25

Mass number

Answer 25

The total number of protons and neutrons in an atom’s nucleus.

Question 26

matter

Answer 26

Anything that takes up space and has mass.

Question 27

Molecule

Answer 27

Two or more atoms held together by covalent bonds.

Question 28

Neutron

Answer 28

A subatomic particle having no electrical charge (electrically neutral)

Question 29

Nonpolar covalent bond

Answer 29

A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity.

Question 30

Orbital

Answer 30

The three-dimensional space where an electron is found 90% of the time.

Question 31

Polar covalent bond

Answer 31

covalent bond between atoms that differ in electronegativity.

Question 32

POtential energy

Answer 32

The energy that matter possesses as a result of its location or spatial arrangement (structure).

Question 33

Product

Answer 33

A material resulting from a chemical reaction.

Question 34

proton

Answer 34

A subatomic particle with a single positive electrical charge

Question 35

Radioactive isotope

Answer 35

An isotope (an atomic form of a chemical element) that is unstable; the nucleus decays spontaneously, giving off detectable particles and energy.

Question 36

Radiometric dating

Answer 36

A method for determining the absolute age of rocks and fossils, based on the half-life of radioactive isotopes.

Question 37

Reactant

Answer 37

A starting material in a chemical reaction.

Question 38

Salt

Answer 38

A compound resulting from the formation of an ionic bond; also called an ionic compound.

Question 39

Single bond

Answer 39

A single covalent bond; the sharing of a pair of valence electrons by two atoms.

Question 40

Trace element

Answer 40

An element indispensable for life but required in extremely minute amounts.

Question 41

Valence

Answer 41

The bonding capacity of a given atom; the number of covalent bonds that an atom can form, which usually equals the number of unpaired electrons in its outermost (valence) shell.

Question 42

Valence electrons

Answer 42

An electron in the outermost electron shell.

Question 43

Valence shell

Answer 43

The outermost energy shell of an atom, containing the valence electrons involved in the chemical reactions of that atom.

Question 44

Van der Waals reactions

Answer 44

Weak attractions between molecules or parts of molecules that result from transient local partial charges.