When group 2a elements form ions, they

They lose two electrons.

Explanation:

When an atom loses are gain the electrons ions are formed.

There are two types of ions.

Anion

Cation

1 = Anion

It is formed when an atom gain the electrons. when atom gain electron negative charge is created on atom. For example.

X + e⁻ → X⁻

2= Cation

It is formed when an atom loses the electrons. when atom lose electron positive charge is created on atom. For example.

X → X⁺ + e⁻

There are two valance electrons in group two elements. They loses two electron to complete the octet and form cation with a charge of +2.

For example:

Mg → Mg⁺² + 2e⁻

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.