1
Q
Atom
A
smallest unit of matter. Has the properties of the element.
2
Q
Proton
A
positively charged subatomic particle in the nucleus (+1)
3
Q
 Neutron
A
neutral subatomic particle in the nucleus (no charge)
4
Q
Electron
A
negatively charged subatomic particle outside of the nucleus (-1)
5
Q
Nucleus 
A
center of an atom, has protons and neutrons
6
Q
Atomic number
A
number of protons, identifies the atom
7
Q
Mass number
A
number of protons and neutrons
8
Q
Group 
A
column on the periodic table, has the same number of valence
electrons
9
Q
Period 
A
row on the periodic table
10
Q
Valence electrons
A
electrons in the outermost energy shell, they determine reactivity 
