i) Which of these cannot form ionic bond ? Why ?
Ans. ‘A’ cannot form ionic bond. Its valence electrons are 4. It is difficult to lose or gain 4e“ to get octet configuration. So it forms covalent bond [Z of A is 6. So it is carbon (C)].
ii) Which of these cannot form covalent bond ? Why ?
Ans. ‘B’ cannot form covalent bond. Its valence electrons are 1 only. So it is easy to donate for other atom and become an ion. So it can form ionic bond [Z of B is 11.
: So it is Sodium (Na)].
iii) Which of these can form ionic as well as covalent bonds ?
Ans. Element 'C' can form ionic as well as covalent bonds. Atomic number of Cl is 17. It is able to participate with Na in ionic bond and with hydrogen in HCZ molecule as covalent bond.