Chapter 2 The Chemical Context of Life Flashcards
anion
a negatively charged ion
atom
The smallest unit of matter that retains the properties of an element.
atomic mass
The total mass of an atom, numerically equivalent to the mass in grams of 1 mole of the atom. (For an element with more than one isotope, the atomic mass is the average mass of the naturally occurring isotopes, weighted by their abundance.)
atomic nucleus
An atom’s dense central core, containing protons and neutrons.
atomic number
The number of protons in the nucleus of an atom, unique for each element and designated by a subscript.
cation
a positively charged ion
chemical bond
An attraction between two atoms, resulting from a sharing of outer-shell electrons or the presence of opposite charges on the atoms. The bonded atoms gain complete outer electron shells.
chemical equilibrium
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.
chemical reaction
The making and breaking of chemical bonds, leading to changes in the composition of matter.
compound
A substance consisting of two or more different elements combined in a fixed ratio.
covalent bond
A type of strong chemical bond in which two atoms share one or more pairs of valence electrons.
dalton
A measure of mass for atoms and subatomic particles; the same as the atomic mass unit, or amu.
double bond
A double covalent bond; the sharing of two pairs of valence electrons by two atoms.
electron
A subatomic particle with a single negative electrical charge and a mass about 1/2,000 that of a neutron or proton. One or more electrons move around the nucleus of an atom.
electron shell
An energy level of electrons at a characteristic average distance from the nucleus of an atom.
electronegativity
The attraction of a given atom for the electrons of a covalent bond.
element
Any substance that cannot be broken down to any other substance by chemical reactions.
energy
The capacity to cause change, especially to do work (to move matter against an opposing force).