A set of atoms with a specific number of protons.
A one or two-letter 'chemical symbol' is used to represent each element. The first letter is always capitalized. In the cases where a second letter is used, it is never capitalized.
|Alkali metals||Alkaline earth metals||Pnictogen||Chalcogens||Halogens||Noble gases|
A Variation of a specific element with a specific number of neutrons. Different isotopes of the same element have different atomic weights. For example Carbon with 7 neutrons has an atomic weight of 13 (6 + 7 = 13).
Isotope notation for Carbon with seven neutrons:
Example sentences and simple deduction:
"For example, carbon-12, carbon-13 and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13 and 14 respectively. The atomic number of carbon is 6, which means that every carbon atom has 6 protons, so that the neutron numbers of these isotopes are 6, 7 and 8 respectively." 
Broad and general discussions may break the periodic table into just three classifications as shown: