NCERT 10th Class Science Chapter Metals and Non-Metals
All the materials around us are made up of chemical elements, which are found in the earth crust. Earth is the source of coal, petroleum, graphite, diamond and many other minerals of metals and non-metals. We get various useful things like gasoline, kerosene, wax, coal gas and natural gas from the natural resources, which are made up of many non-metals. These elements occur as minerals and rocks in the earth's crust. Some of these elements like oxygen, nitrogen and carbondioxide occur in atmospheric air.
There are more than 115 elements known at present 80% of these elements are metals and rest are non-metals.
On the basis of their properties , all the elements can be divided into two main groups: metals and non-metals.
Metals are the elements that conduct heat and electricity and are malleable and ductile. Some of the examples of metals are : Iron, Aluminium, Copper, Silver, Gold, Platinum, Zinc.
Metals are the elements which form positive ions by losing electrons (or donating electrons). Metals are known as electropositive elements because they can form positive ions by losing electrons.
The most abundant metal in the earth’s crust is aluminium.
Non-metals are the elements that does notconduct heat and electricity and are neither malleable nor ductile. They are brittle. Some of the examples of non-metals are : Carbon, Sulphur, Phosphorus, Silicon, Hydrogen, Oxygen, Nitrogen. The two allotropic forms of carbon element, diamond and graphite are also non - metal.
Non-metals are the elements which form negative ions by gaining electons. Non-metals are known as electronegative elements because they can form negative ions by gaining electrons.
Carbon is one of the most important non-metals, as life on this earth is based on carbon compound because the carbon compounds like proteins, fats, carbohydrates, vitamins and enzymes etc. are essential for the growth and development of living organisms.
The most abundant non-metal in the earth’s crust is oxygen.
Position of Metals and Non-Metals in The Periodic Table
(i) The elements which are placed on the left hand side (except hydrogen) and in the centre of the periodic table are called metals. Such as sodium, potassium, magnesium, calcium, iron, copper zinc etc.
(ii) The elements which are placed on the right hand side of the periodic table are called non-metals such as oxygen, nitrogen, chlorine, fluorine etc. These metals and non-metals are separated from each other in the periodic table by a zig-zag line. The elements placed in the zig-zag line show some properties of metals and some properties of non-metals are called metalloids. Such as boron(B), silicon(Si), germanium(Ge), arsenic(As), antimony(Sb), tellurium(Te) and polonium(Po).
(iii) The position of metals, non-metals and metalloids are shown in a simple form in figure..
Metals present at the extreme left are known as light metals, while those are present in the centre of the periodic table are called heavy metals or transition metals.
(iv) The elements at the extreme left of the periodic table are most metallic and those on the right are least metallic or non-metallic.
Thus, metallic character decreases on going from left to right side in the periodic table. For example