1
Number of protons and neutrons
2
A tiny, negatively charged particle that moves around the nucleus of an atom.
3
A substance that cannot be broken down into simpler substances
4
A subatomic particle that has no charge and that is found in the nucleus of an atom
5
Center of an atom
6
Anything that has mass and takes up space
7
A subatomic particle that has a positive charge and that is found in the nucleus of an atom
8
Horizontal row of elements in the periodic table
9
Smallest unit of an element
