Sancho's Non Metals & Their Compound Lesson Notes Ordinary Level

NON –METALS AND THEIR COMPOUNDS CHEMISTRY LESSON NOTES FOR ORDINARY LEVEL

OBJECTIVES OF THE TOPIC:

Non – metals are located at the top right-hand side of the periodic table. In a period, the

nonmetallic character increases as we move from left to right. In group, the non – metallic

character decreases on going down a group. Non – metals are much less in number than metals.

They are usually gases at room temperature, neither malleable nor ductile, poor conductor of heat

and electricity.

Non-metals: Are those atoms which ionized by electron gain to become negatively charged ion.

Examples: Cl + ē Cl –

H + ē H –

Hence, non-metal reacts by accepting electrons. The ability to accept electron

Electronegativity: Is a measure of attraction of an atom for the element in the chemical bond.

Electronegativity: Is an ability of an element to attract electrons towards itself.

The energy associated with electron acceptance is called electron affinity.

Electron affinity: Is the energy released when one electron is added to the gaseous atom.

Electron affinity: Is the enthalpy (heat) change taking place when an isolated gaseous atom

accepts an electron to form a monovalent gaseous anion.

The process can be expressed as

Cl(g) + ē Cl –

(g)

Depending on the element, the process of adding an electron can be either

NOTE: When the first electron is added to the gaseous atom, it forms a uninegative ion

(the first electron affinity). Now, if an electron is added to the uninegative ion, it

experiences a repulsive force from the anion. As a result, the energy has to be supplied

to overcome the repulsive force. Thus, in order to add the second electron energy is

required rather than released.

O(g) + ē O – (g) ∆H1 = - 141 KJ

O – (g) + ē O 2 – (g) ∆H2 = + 780KJ