(b) What are the orbitals of an atom?

(c) How many orbitals are there in the s, p, and d subshells? What are the shapes of these orbitals?

Some elements such as [tex]^{13}\text{Al}, ^{15}\text{P}, ^{16}\text{S}, ^{19}\text{K}, ^{35}\text{Br},[/tex] and [tex]^{36}\text{Kr}[/tex] are given.

(i) Describe the electronic configuration for each element.
(ii) Describe the valence electrons of the elements listed.
(iii) Give a Lewis symbol for each element.

(a) What is meant by the term electronegativity of an element?
(b) What does the type of chemical bonding depend on?

(i) Classify the main types of chemical bonding. Among them, which force is the strongest?
(ii) Mention the intermolecular forces.

Terms:
- Valence electrons are the electrons in the outermost shell of an atom.
- The Aufbau principle states that electrons are filled in lower energy atomic orbitals before filling higher energy ones.
- Pauli's exclusion principle states that no more than two electrons can occupy the same orbital, and two electrons in the same orbital must have opposite spins.
- Hund's rule states that every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin.

Ionic Bonding:
- Ionic bonding (electrovalent bonding) results from the transfer of electrons from one atom having small ionisation energy to another atom having a large electron affinity. Electrostatic attractions between cations (positively charged ions) and anions (negatively charged ions) are formed.