(i)

Characteristics of ionic compounds

1. They are solid at room temperature
2. They have high boiling point
3. They have high density
4. They are generally soluble in polar solvents/water
5. They conduct electricity in molten state/in aqueous solution
6. They have high melting point
7. They exist in crystalline form

(ii)

Why helium does not form a compound

1. Helium is an element with completely filled valence shell/it is stable/has maximum of 2 electrons in its shell
2. It therefore does not require transfer (or acceptance or sharing) of valence electrons for stability

(i)

Characteristics of ionic compounds

1. They are solid at room temperature
2. They have high boiling point
3. They have high density
4. They are generally soluble in polar solvents/water
5. They conduct electricity in molten state/in aqueous solution
6. They have high melting point
7. They exist in crystalline form

(ii)

Why helium does not form a compound

1. Helium is an element with completely filled valence shell/it is stable/has maximum of 2 electrons in its shell
2. It therefore does not require transfer (or acceptance or sharing) of valence electrons for stability