The nuclear charge of an atom is the measure of the effect of attraction between the protons in the nucleus and the outer electron
Shielding is the effect of the inner shells of electrons on weakening the attraction between the protons in the nucleus and the outer electron.
Ionisation energy is a measure of the amount of energy required to remove an outer electron from an atom creating a positively charged ion.
Group 1 is the first group in the periodic table containing elements that are commonly known as the Alkali metals. They are all metals and increase in reactivity down the group and when reacted with water form alkali solutions