Non-metals

Introduction

Non-metals behave just opposite to that of metals in many ways. Physically, a nonmetal is characterizd by its low melting point, boiling point, and the density. A nonmetal is typically brittle in its solid form and it has a very poor thermal conductivity as well as the electrical conductivity. Chemically, nonmetals tend to have relatively high ionization energy, electron affinity, and electronegativity. They gain or share electrons when they react with few other elements and chemical compounds. Non-metals are divided into Seventeen elements : most of them are are gases (hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon and radon); one is a liquid (bromine); and a few are solids (carbon, phosphorus, sulfur, selenium, and iodine). Metalloids such as boron, silicon, and germanium are sometimes counted as nonmetals.

 

Table of Contents

1. Introduction

2. Physical properties of non-metals

3. Valency of non-metals

4. Chemical properties of non-metals

5. Comparison between metals and non-metals

 

Physical properties of non-metals

  1. Non-metals are Non-malleable or brittle hence, they can easily break into pieces when stretched or forced with weight. For example, Sulphur and phosphorous are brittle non-metals.

  2. Non-metals are Non-ductile, which means we cannot craft them into thin wires as they brake into pieces when stretched

  3. Non-metals are the bad Conductors of Heat and Electricity as they do not have free electrons. Free  electrons are accountable for the transfer of heat and electricity

  4. Non-metals are non-lustrous so which cannot be polished like metals.

  5. Non-metals vary in their form, hence that are found in solid, liquid or gases at room temperature.

  6. Non-metals are characterised by their low melting and boiling points when compared to the metals.

  7. Non-metals are not as strong as metals.

  8. Mass and density of non-metals are low, hence they are lighter.

  9. Non-metals are non-sonorous.

 

Valency of non-metals

The number of electrons accepted by a non-metal is called the Valency of a non-metal. For example, one atom of chlorine accepts 1 electron to form a negative chloride ion (Cl–), so chlorine is a non-metal. So, an atom of chlorine gains 1 electron hence, the valency of chlorine is  Cl      +    e-    → Cl–
 

Chemical properties of non-metals

Non-metals are also called electronegative elements because the non-metal atom form negatively charged ion by accepting electrons. The following are the important chemical reactions of non-metals.

1. Reaction of Non-metals with Oxygen
: All non-metals react with oxygen to form acidic or neutral oxides. For example, Carbon forms acidic carbon dioxide on reacting with oxygen.

 C      +         O2      →    CO2
 (Carbon) ( oxygen ) (Carbon Dioxide)                                                            

In the same way, Sulphur reacts with oxygen of the air to form acidic Sulphur dioxide.

S      +            O2         →         SO2

(Sulphur  ) ( oxygen )        (Sulphur Dioxide)                

          

2. Reaction of Non-metals with Water: Non-metals do not react with water!



3. Reaction of Non-metals with Dilute Acids: Non-metals do not react with dilute acids and don’t displace hydrogen from dilute acids, because non-metals are electron acceptor. So, they cannot supply electrons to H+ ions. So, they do not displace hydrogen from dilute acids.



4. Reaction of Non-metals with Chlorine : Non-metals react with chlorine to form covalent chlorides. For example,

       H2      +         Cl2         →      2HCl
 (Hydrogen)     (Chlorine)         (Hydrogen chloride)           

   P4      +         6Cl    →        4PCl3

(Phosphorous)    (Chlorine)   (Phosphorous trichloride)                    

5. Reaction of Non-metals with Hydrogen

   H2      +           S         →  H2S

(Hydrogen)    ( sulphur)  (Phosphorous trichloride)                     

   N2      +      3H2         →      2NH3
(Nitrogen)     (Hydrogen)       (Ammonia)                 

 

Relative comparison between metals and non-metals

S.No

Property

Metals

Non-Metals

1

Physical State

Metals are solid at room
temperature with the only exception for mercury and gallium they are liquids.

Non-metals generally
exist in their solids and gaseous, form except Bromine.

2

Melting and boiling points

Metals generally have
high m.pt and b.pt except for gallium and caesium.

Non-metals have low
m.pt and b.pt except diamond and graphite.

3

Density

It is generally high.

It is generally low.

4

Malleability and Ductility

Malleable and ductile.

Neither malleable nor
ductile.

5

Electrical and thermal conductivity

Good conductors of heat
and electricity.

Generally poor
conductors of heat and electricity except for graphite.

6

Lustre

Poses shining lustre.

Do not have lustre
except iodine.

7

Sonorous sound

Give sonorous sound
when struck.

Does not give
sonorous sound.

8

Hardness

Generally hard except
Na, K

Solid non-metals are
generally soft except diamond.

 





img-1

img-1

img-1

Course List