Oracle IAS, the best coaching institute for UPSC/IAS/PCS preparation in Dehradun brings to you UKPCS Science Chemistry (paper 6).
What is an element? How many elements are there?
- An element is a substance that is made entirely from one type of atom. For example, the element hydrogen is made from atoms containing a single proton and a single electron. If you change the number of protons an atom has, you change the type of element it is.
- Currently, scientists know of 118 different elements. Some, like gold, silver, copper and carbon, have been known for thousands of years. Others, such as meitnerium, darmstadtium and ununquadium, have only recently been created by scientists. All known elements are arranged on a chart called the Periodic Table of Elements.
- These elements can further be classified into metals, non-metals and noble gases.Elements to the left of the line are considered metals. Elements just to the right of the line exhibit properties of both metals and non metals and are termed metalloids or semimetals. Elements to the far right of the periodic table are non metals.
Difference between metal and non metals:
- Metals have one to three electrons in their outer shell, whereas non-metals have four to eight electrons.
- Metals are malleable, which means they can be beaten to thin sheets. On the other hand, non-metals are very brittle.
- Metals have a high to moderate density, whereas non-metals have low to moderate density.
- Metals are opaque and non-metals are transparent.
- Metals are present in solid form at room temperature, and non-metals are present in solid and liquid forms at room temperature.
- Unlike non-metals, metals are ductile, which means they can be stretched into wires.
- Metals have a metallic luster, while non-metals do not.
- Metals tend to lose their valence electrons, but non-metals share or gain valence electrons.
- Metals are good conductors of electricity and heat, but non-metals are poor conductors.
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