Atomic radius increases as we move down group 2.

First ionisation energy decreases as we move down group 2 because:

• Atomic radius increases due to the addition of extra energy levels, increasing the distance between the outermost electron and the nucleus.
• The increased number of inner electrons provides greater shielding, reducing the effective nuclear charge experienced by the outermost electron.
• The increased distance and shielding effect weaken the electrostatic attraction between the nucleus and the outermost electron, making it easier to remove.

The graph below shows in first ionisation energy as we move down group 2.

Reactivity increases as we move down group 2.

This is because the outer electrons are further away from the nucleus and are shielded by more inner electrons. This makes it easier for the elements to lose their outer electrons and form positive ions.

M + 2H₂O ➔ M(OH)₂ + H₂

Because each metal atom is oxidised, losing 2 electrons to form a 2+ ion, while water gains these 2 electrons and is reduced.

The group 2 metals acts as a reducing agent in this reaction.

2M + O₂ ➔ 2MO

Metal + acid ➔ salt + hydrogen

M_(s) + 2HCl_(aq) ➔ MCl_2(aq) + H_2(g)

Atomic radius increases down a group because:

• Additional energy levels (shells) are added as we move down a group, increasing the distance between the outer electrons and the nucleus.
• The increased number of inner electrons provides greater shielding, reducing the effective nuclear charge experienced by the outer electrons.
• With more shielding and a larger distance from the nucleus, the outermost electrons are held less tightly, resulting in a larger atomic radius.

The graph below shows the trend in atomic radius as we move down group 2.