Atom

The smallest piece of matter that can exist by itself.

• neutron

• proton

• atom

• molecule

The heaviest part at the center of an atom.

• the heart

• the core

• the nucleus

• the middle

Extremely small pieces of matter that are smaller than an atom.

• molecules

• mass numbers

• subatomic particles

• subatoms

The part of an atom with a negative electrical charge, which moves around the atom's nucleus.

• isotope

• proton

• electron

• mass number

A type of particle with a positive electrical charge that is found in the nucleus of all atoms.

• proton

• electron

• positron

• optimist

The number of protons found in the nucleus of an atom.

• nuclear number

• atomic number

• nucleus number

• core number

The total number of protons and neutrons in an atom.

• nil number

• final number

• total number

• mass number