Question

Write the electronic configuration of ${}_3{}^7\mathrm{Li}$ and hence its valency as well as the formulae of its chlorides and oxides.

Answer 1

• Given the atomic number of lithium is 3.
• Atomic number is the number of protons in an atom.
• In an electrically neutral atom, the number of electrons and protons are equal. Hence silicon will have 3 electrons.
• Electronic configuration is the arrangement of electrons in different energy levels around the atom.
• Thus the electronic configuration:2,1. Since it has 1 electron in the outermost shell, the valency is 1. It has to give up this one electron to complete its octet.

Chloride:

• Chlorine has 17 electrons and the electronic configuration:2,8,7. It has one electron less than the stable electronic configuration.
• Thus one lithium atom and one chlorine atoms can combine together to form lithium chloride molecule ($\mathrm{LiCl}$).
• Hence there will be a transfer of one electron from lithium atom to chlorine atom. Thus the valency of lithium and chlorine are satisfied.

Oxide:

• Oxygen atom has 8 electrons and the electronic configuration:2,6. It has two electrons to complete octet. Valency of oxygen is 2.
• When oxygen and lithium atoms come together there will be a transfer of electron from lithium atom to oxygen atom.
• Thus one oxygen atoms and two lithium atom can combine together to form lithium oxide (${\mathrm{Li}}_2\mathrm{O}$).