Chemistry Vocabulary

These vocabulary words appear on the Chemistry CBA in addition to being tested

on the Chemistry Vocabulary Test.

atom

DEFINITION/MEANING

the smallest unit of an element that still represents that element.

subatomic particle

DEFINITION/MEANING

the particles that make up an atom: protons, electrons, and neutrons.

neutron

DEFINITION/MEANING

A neutral particle in the nucleus of an atom that has a mass of 1 amu.

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.

isotopes

DEFINITION/MEANING

atoms of the same element that have different numbers of neutrons.

ion

DEFINITION/MEANING

an atom that is no longer neutral because it has gained or lost electrons.

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 (+).

radioactive

DEFINITION/MEANING

any element that spontaneously emits radiation.

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.

product

DEFINITION/MEANING

The resulting substance(s) that are produced by a chemical reaction.

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

Law of Conservation of Mass

DEFINITION/MEANING

law that states that the total mass of the reactants before a chemical reaction is the same as the total mass of the products after the chemical reaction; also referred to as The Law of Conservation of Matter.