JSS 3: ORBITALS

An orbital is a region around the nucleus of an atom where electrons can be found 

                          Atom

An atom is the smallest particle of an element that can take part in a chemical reaction. It consists of a nucleus at the center, which contains positively charged protons and neutral neutrons, and negatively charged electrons that orbit the nucleus in shells. 

                 Sub-particles of an atom

The sub-particles of an atom are:

I. Proton

II. Electron

III. Neutron

                       Types of orbitals

The different types of orbitals are:

I. s-orbital

II. p-orbital

III. d-orbital

IV. f-orbital

                               S-orbital

I. S-orbitals are spherical in shape 

II. They contain maximum of two electrons

III. They have the lowest energy level in any given shell

              

                               P-orbital

I. P-orbitals are dumb-bell in shape

II. They contain maximum of six electrons

III. There are three types of p-orbitals Px, Py and Pz

                              D-orbital

I.  D-orbitals are double dumb-bell in shape

II. They contain maximum of ten electrons

III. There are five types of d-orbitals 

                              F-orbital

I. F-orbital has complex lobed shape 

II. They contain maximum of fourteen electrons.

III. There are seven types of f-orbitals

           Electronic configurations

Electronic configuration is the arrangement of electrons in the orbitals of an atom.

1s 2s 3s 4s 5s...

     2p 3p 4p 5p...

           3d 4d 5d...

                 4f 5f ...

1s 2s 2p 3s 3p 4s 3d 4p 5s...

Examples:

Write the electronic configurations of the following elements:

1. Hydrogen (₁H)

2. Sodium (₁₁Na)

3. Calcium (₂₀Ca)

Solution:

1. Hydrogen: 1s¹

2. Sodium: 1s² 2s² 2p⁶ 3s¹

3. Calcium: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

                 Electron shell

Electron shell is the orbit that electrons follow around the nucleus of an atom.

The different types of electron shells are: K, L, M, N,...shells.

The closest shell to the nucleus is the K shell

                   Energy sublevels

Energy sublevels are the divisions within energy levels of an atom. They are  designated by the letters s, p, d, and f.

       The electron configuration of the sulphur atom is:

Sulphur, Z=16: 1s² 2s² 2p⁶ 3s² 3p⁴

                 

                 Orbital diagrams

    The arrangement of electrons in a ground state atom can be shown as: