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 DefinitionBack to Top
"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 TableBack to Top
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.
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 MetalsBack to Top
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.
|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|
Characteristics of Non MetalsBack to Top
- The non-metals are electronegative elements because they have tendency to gain electrons.
- Non-metals (except graphite) are poor conductors of heat and they do not conduct electricity.
- Non-metals are neither malleable nor ductile.
- Non-metals are neither lustrous nor sonorous.
- Non-metals have low melting and boiling points.
- The solid non-metals are generally soft and brittle.
- Bromine is the only non-metal which is liquid at room temperature.
Properties of Non MetalsBack to Top
Physical Properties of Non Metals
- Hardness - Non-metals are generally soft and brittle. Few exceptions are boron and carbon (in the form of diamond) ar vary hard.
- 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.
- Malleability and ductility - Non-metals are neither malleable nor ductile. Due to very weak inter atomic or intermolecular attractive forces.
- Luster - Non-metals are not lustrous and they have dull appearance. Due to absence of free electrons.
- Melting and boiling points - Non-metals have low melting and boiling points. Due to weak intermolecular forces.
- 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.
- Sonority - Non-metals are non-sonorous. They do not produce sound when hit by an object.
- 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.
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.
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.
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.
2Na + Cl2 $\rightarrow$ 2Na+Cl-
2NaBr + Cl2 $\rightarrow$ 2NaCl + Br2
Metals and Non MetalsBack to Top
||Shiny - usually solid
||Dull - can be solid, liquid or gas
||Usually strong - can be hammered into shape
||Usually weak (brittle) - can break when hammered
||Usually hard - difficult to scratch||Usually soft - easier to scratch
||Density||Usually high - heavy for its size
||Usually low - light for its size|
||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 MetalsBack to Top
- It is essential for life as it is used by living beings for respiration.
- It supports combustion reaction in homes, factories and missiles.
- Used to provide respiration in hospitals.
- Ozone prevent harmful UV rays from entering the earths surface
- In the form of nitrates and nitrites it is used by plants for their growth.
- It is used to make fertilizers.
- Used as disinfectant to purify water and kills germs.
- Used in the form of bleaching powder for bleaching clothes, wool and textiles.
- Used in making sulfuric acid, an important industrial chemical used to obtain sulfate, salts of variety of metals.
- Used sulphates salts in fertilizers.
- Used in making matchsticks.
- Used in making crackers.
- Used as an antiseptic.
- Iodine in alcohol solution is used for healing of wounds.
- Black material inside pencil is graphite lead.
- Soft, slippery and used for writing purpose.
Most Reactive Non MetalsBack to Top
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?Back to Top
Graphite which is an allotrope of carbon can conduct electricity and it is used for making electrodes.