Chemistry Vocabulary
These vocabulary words appear on the Chemistry CBA in addition to being tested
on the Chemistry Vocabulary Test.
subatomic particle
DEFINITION/MEANING
the particles that make up an atom: protons, electrons, and neutrons.
proton
DEFINITION/MEANING
positively charged particle in the nucleus of an atom that has a mass of 1 amu.
nucleus
DEFINITION/MEANING
the positively charged region in the center of an atom where most of an atom’s mass is located; contains protons and neutrons.
Mass = Protons + Neutrons
electron
DEFINITION/MEANING
a negatively charged particle that occupies the space in an atom outside the nucleus and has almost zero amu.
valence electron DEFINITION/MEANING
the electrons in the outermost shell (orbital) of an atom that participates in chemical bonding.
electron cloud
DEFINITION/MEANING
the region surrounding an atom’s nucleus where one or more electrons are most likely to be found.
energy level
DEFINITION/MEANING
The general region of the electron clouds where specific numbers of electrons are located; also called “orbitals”.
electron dot diagram
DEFINITION/MEANING
Also called “Lewis Structure”; a model that represents valence electrons in an atom as dots around the element’s chemical symbol.
atomic number
DEFINITION/MEANING
the number of protons in an atom of an element.
A = P = E Atomic Number = Protons = Electrons**
**for a neutral atom
mass number
DEFINITION/MEANING
the sum of the number of protons and neutrons in an atom.
M-A =N Mass – Atomic Number = Neutrons
average atomic mass
DEFINITION/MEANING
the average mass of the element’s isotopes, weighted according to the abundance of each isotope.
atomic mass unit (amu)
DEFINITION/MEANING
the unit used to measure atomic mass which is equal to 1.6727 x 10-24 grams.
positively charged atom DEFINITION/MEANING
When a neutral atom loses one or more negatively charged electron(s) and becomes positively charged due to having more protons (+) than electrons (-).
negatively charged atom DEFINITION/MEANING
When a neutral atom gains one or more negatively charged electron(s) and becomes negatively charged due to having more electrons (-) than protons (+).
periodic table
DEFINITION/MEANING
a chart of the elements arranged into groups (columns) and periods (rows) according to their physical and chemical properties.
group
DEFINITION/MEANING
also called a “family”; a vertical column on the periodic table containing elements that have similar reactivity and other chemical properties due to equivalent number of valence electrons.
period
DEFINITION/MEANING
a horizontal row on the periodic table containing elements with the same number of energy levels (orbitals); but elements do not necessarily have similar properties.
chemical bond
DEFINITION/MEANING
a force that holds two or more atoms together due to elements sharing or transferring electrons to other elements.
ionic bond
DEFINITION/MEANING
the chemical bond formed due to the attraction between positively and negatively charged ions in an ionic compound.
covalent bond
DEFINITION/MEANING
a chemical bond formed due to the sharing of valence electrons in a covalent compound.
molecule
DEFINITION/MEANING
A group of atoms chemically bonded together that represents the smallest unit of a compound
chemical formula
DEFINITION/MEANING
an expression that indicates the number and types of elements that a molecule is composed of
subscript
DEFINITION/MEANING
The small number next to the symbol of an element that indicates the number of atoms present in the chemical formula
chemical reaction
DEFINITION/MEANING
a process in which atoms of one or more substances rearrange to form one or more new substances with new physical and chemical properties; a chemical change.
chemical equation
DEFINITION/MEANING
a description of a chemical reaction using element symbols and chemical formulas.
reactant
DEFINITION/MEANING
The initial substance(s) in a chemical reaction; the elements that react.
coefficient
DEFINITION/MEANING
a large number placed in front of an element symbol or chemical formula in an equation that represents the number of molecules.
balanced chemical equation
DEFINITION/MEANING
A chemical equation with the same amount of atoms from each element on either side of a chemical equation