1
Q
Mass number (A)
A
Protons + neutrons
Top left on periodic table
2
Q
Atomic number (Z)
A
Number of protons
Bottom left on periodic table
3
Q
Ground state
A
The energy level normally occupied by an electron
4
Q
Excited state
A
When an electron is at a higher, less stable energy level
5
Q
Filling energy levels /aufbau’s principle
A
6
Q
Number of electrons in S orbital
A
2
7
Q
Number of electrons in P orbital
A
6
8
Q
Number of electrons in D orbital
A
10
9
Q
Valence electrons
A
Electrons in the outermost energy level
10
Q
Isotope
A
An element with a different number of neutrons
11
Q
Number of electrons in f orbital
A
14
