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The periodic table classifies elements into families that have similar physical properties and chemical characteristics. These families of related elements are called groups. Materials that are poor conductors of electricity are generally considered nonmetals. Earths atmosphere is composed of nonmetallic elements but lightning can break down the electron bonds and allow huge voltages to make their way to the ground.


Nonmetals are the second class of elements. With the exception of hydrogen the 18 nonmetals appear to the right side of the periodic table. Nonmetals tend to gain enough electrons to completely fill the s and p orbitals of their outermost energy level. Elements which can form negative ions by gaining electrons are called nonmetals.

Non Metals Definition

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Definition of Nonmetals

"Non metals are the elements which form negative ions by accepting or gaining electrons. They do not conduct electric current" Hydrogen is an exception it is a non-metal which loses electron to form positive ion.

As elements progress from group 13 to 17 they show a shift from metallic characteristics to properties of the nonmetals, but the distinctions are not cut and dried. Non-metals usually have 4, 5, 6 or 7 electrons in their outermost shell. During chemical reactions, non-metals can form negative ions by gaining electrons.

The most abundant non-metal in the earths crust is oxygen. The major non-metals in the earths crust in the decreasing order of their abundance are oxygen, silicon, phosphorus and sulfur.

Non Metals on the Periodic Table

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The way to classify elements is as metals, nonmetals or metalloids. The periodic table arrange elements so that one can place a given element easily into one of these categories. Nonmetals occupy the upper right hand portion of the periodic table. There are fewer nonmetals than metals.

Nonmetals occupy the upper right hand portion of the periodic table. There are fewer nonmetals than metals. The Periodic Table Non Metals is diagrammatically represented below.

Non Metals on the Periodic Table

The most typically nonmetallic elements are found in Group VII. These elements are called the halogens and include chlorine and bromine. Group VIII contains the noble gases which include helium and neon.

List of Non Metals

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Non-metals are electronegative in character. It exist in all the three states that is solid, liquid and gas. it is quite abundant on the earth. They are the major constituent of the atmosphere oxygen, nitrogen and noble gases etc.

Totally 18 elements are nonmetals and they on place on the extreme right side of the periodic table. The examples of non-metals are tabulated below.

S.No
Non-metals
Symbol
1 Hydrogen H
2
Helium
He
3
Carbon
C
4
Nitrogen
N
5
Oxygen
O
6
Fluorine
F
7
Neon
Ne
8
Phosphorus
P
9
Sulfur
S
10
Chlorine
Cl
11
Argon
Ar
12
Selenium
Se
13
Bromine
Br
14
Krypton
Kr
15
Iodine
I
16
Xenon
Xe
17
Astatine
As
18
Radon
Rn

Non-metals are not sonorous, malleable or ductile, they are weak and they do not conduct heat or electricity. Graphite is exception and it is a good conductor os electricity.

Characteristics of Non Metals

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  1. The non-metals are electronegative elements because they have tendency to gain electrons.
  2. Non-metals (except graphite) are poor conductors of heat and they do not conduct electricity.
  3. Non-metals are neither malleable nor ductile.
  4. Non-metals are neither lustrous nor sonorous.
  5. Non-metals have low melting and boiling points.
  6. The solid non-metals are generally soft and brittle.
  7. Bromine is the only non-metal which is liquid at room temperature.

Properties of Non Metals

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The non metals properties are given below.

Physical Properties of Non Metals


  1. Hardness - Non-metals are generally soft and brittle. Few exceptions are boron and carbon (in the form of diamond) ar vary hard.
  2. Density - Non-metals have low densities. They do not have any permanent electrical polarity and the intermolecular attractive forces holding these molecules are very weak.
  3. Malleability and ductility - Non-metals are neither malleable nor ductile. Due to very weak inter atomic or intermolecular attractive forces.
  4. Luster - Non-metals are not lustrous and they have dull appearance. Due to absence of free electrons.
  5. Melting and boiling points - Non-metals have low melting and boiling points. Due to weak intermolecular forces.
  6. Thermal and electrical conductivity - non-metals are poor conductors of heat and electricity. Due to absence of free electrons available for electrical conduction in non-metals.
  7. Sonority - Non-metals are non-sonorous. They do not produce sound when hit by an object.
  8. Allotropy - Non-metals exhibit allotropy. It exist more than one structural form.


Chemical Properties of Non Metals


  • Electronegative character

The non-metals are electronegative elements. They have the tendency to gain electrons and undergo reduction.

Cl + e- $\rightarrow$ Cl-
S + 2e- $\rightarrow$ S2-
O + 2e- $\rightarrow$ O2-

  • Reaction with oxygen

Non-metals react with oxygen to form oxides. These oxide are covalent in nature and are generally gaseous. Most of these oxide when dissolved in water give acidic solution.

S + O2 $\rightarrow$ SO2
C + O2 $\rightarrow$ CO2
P4 + 5O2 $\rightarrow$ 2P2O5

Certain oxides of non-metals are neutral. Some examples are nitrous oxide (N2O), carbon monoxide (CO) etc.

  • Reaction with acids

Non-metals do not displace hydrogen from acids. For the liberation of hydrogen the non-metals should be able to reduce H+ ions to H2 gas supplying electrons. Non-metals are electronegative elements and hence have more tendency to accept electron rather than donating.

  • Reaction with chlorine

Non-metals react with chlorine to form chlorides. These chlorides are covalent in nature and are generally gaseous or liquids.

H2 + Cl2 $\rightarrow$ 2HCl
P4 + 6Cl2 $\rightarrow$ 4PCl3
P4 + 10Cl2 $\rightarrow$ 4PCl5

  • Reaction with hydrogen

Non-metals reacts with hydrogen form hydride which are covalent in nature. Most of these hydride are gases or liquids.

2H2 + O2 $\rightarrow$ 2H2O
N2 + 3H2 $\rightarrow$ 2NH3
H2 + S $\rightarrow$ H2S
  • Oxidizing nature

Non-metals have great tendency to accept electrons, therefore many non-metals act as good oxidizing agents. Fluorine is the strong oxidizing agent among all the non-metals.

Zn + S $\rightarrow$ Zn2+S2-
2Na + Cl2 $\rightarrow$ 2Na+Cl-
2NaBr + Cl2 $\rightarrow$ 2NaCl + Br2

Metals and Non Metals

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The metals and non-metals comparison is tabulated below.

S.No
Property
Metals
Non-metals
1 Appearance
Shiny - usually solid
Dull - can be solid, liquid or gas
2
Strength
Usually strong - can be hammered into shape
Usually weak (brittle) - can break when hammered
3
Hardness
Usually hard - difficult to scratch Usually soft - easier to scratch
4
Density Usually high - heavy for its size
Usually low - light for its size
5
Melting point and boiling point
Usually high Usually low
6
Does it conduct heat?
Usually good conductor
Usually poor conductor
7
Does it conduct electricity?
Usually good conductor
Usually non-conductor

Uses of Non Metals

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Oxygen
  1. It is essential for life as it is used by living beings for respiration.
  2. It supports combustion reaction in homes, factories and missiles.
  3. Used to provide respiration in hospitals.
  4. Ozone prevent harmful UV rays from entering the earths surface

Nitrogen

  1. In the form of nitrates and nitrites it is used by plants for their growth.
  2. It is used to make fertilizers.

Chlorine

  1. Used as disinfectant to purify water and kills germs.
  2. Used in the form of bleaching powder for bleaching clothes, wool and textiles.

Sulfur

  1. Used in making sulfuric acid, an important industrial chemical used to obtain sulfate, salts of variety of metals.
  2. Used sulphates salts in fertilizers.

Red phosphorus

  1. Used in making matchsticks.
  2. Used in making crackers.

Iodine

  1. Used as an antiseptic.
  2. Iodine in alcohol solution is used for healing of wounds.

Graphite

  1. Black material inside pencil is graphite lead.
  2. Soft, slippery and used for writing purpose.

Most Reactive Non Metals

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The most reactive nonmetals are those in group 17 (VII A) on the right side of the periodic table. They tend to accept electrons from the metals to complete their outer valence shells from seven electrons to form full outer shells of eight electrons.

Fluorine is the most reactive non metals and chlorine come the next. The halogens are the most reactive non-metals and are strong oxidizing agents. The halogens become less reactive as the group descends as their oxidizing power decreases.

Do Non Metals Conduct Electricity?

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Non metals usually do not conduct electricity due to non availability of free electrons. An exception is carbon in which in the form of graphite it conducts. Non metals are used as insulators.

Graphite which is an allotrope of carbon can conduct electricity and it is used for making electrodes.