The rows are known as…
Periods
Elements of the same period have the same number of
Electron shells
The columns are known as…
Groups
Elements with the same group have the same number of…
Electrons in the outer shell
An element is…
A substance that cannot be broken down into anything simpler
A compound is…
Two or more different elements chemically bonded together
Molecules are…
Two or more atoms bonded together (they don’t have to be different)
Elements such as O2 and Br2 are…
Diatomic molecules
Mass number is…
The number of neutrons plus the number of protons
The atomic number is…
The number of protons
Isotopes are…
Atoms with different numbers of neutrons e.g. Chlorine