Explanation:
Covalent bond -
This type of bonding takes place between the atoms of same or similar electronegativity , is referred to as covalent bonding .
Ionic bonding -
This type of bonding takes place between the atoms of different electronegativity , is referred to as Ionic bonding .
From the question ,
( a ) F₂ - Covalent bonding ( same atom , hence , same the electronegativity )
( b ) LiBr - Ionic bonding ( the electronegativity difference between Li and Br is high )
( c ) NaNH₂ - Ionic bonding ( the electronegativity difference between sodium and Nitrogen is high )
( d )CH₃CH₃ - Covalent bonding ( since , the electronegativity difference between carbon and hydrogen is similar )