Structure of

Matter UnitVocabulary

Atomic numberThe number of protons in

an atom’s nucleus

Chemical symbol

A shorthand way to write the name of an element.

Example: Ag = Gold

ElectronNegatively charged particles that move

around the nucleus of an atom.

IsotopeAtoms of the same element that have

different numbers of neutrons

Example: Boron – 10 and Boron - 11

NeutronAtomic particle with no charge, neutral, that is

part of an atoms nucleus

Mass numberSum of the numbers of

the protons and neutrons in an atom’s nucleus

Periodic tableA chart of elements

arranged according to repeated changes in

properties

ProtonAtomic particle with a positive charge that is

part of an atom’s nucleus

Quark6 small particles that

make up a neutron and proton

Boiling pointThe temperature at which vapor bubbles from in a liquid form to rise to the

surface, increasing evaporation

DensityDescribes how tightly packed a

substance’s molecules are

Density formulaThe mass per unit volume of a

materialD=M/V

D=density M=mass V=volume

IonA positively or negatively

charged atom

Nonpolar moleculeA molecule that does not have oppositely charged

ends

ToxicHazardous substance that can injure living tissues

Chemical formulaA precise statement that

tells which elements are in a compound and their

ratios

Chemically stableDescribes an atom whose

outer energy level is completely filled with

electrons

CorrosiveHazardous compound that attacks and alters metals,

human tissue or other materials

Covalent bondA type of chemical bond formed by atoms when they share electrons, producing molecules

Chemical bondThe force that holds together

the atoms in a compound, occurs because atoms of

most elements become more stable by gaining, losing and

sharing electrons