What is Elements ?
Element Definition :-
- Group of same type of atoms is known as Element. For example : Gold, silver, iron, sulphur etc. Till date 118 elements are known.
- The molecule of an element is made up of a combination of one or more than one atoms. For example : Molecules of Argon, Helium etc. are made up of a single atom of the element while the two types of molecules of oxygen are O2 and O3 which are made up of two and three atoms of oxygen, respectively. O2 is known as di-oxygen and O3 is known as Ozone.
- The number of atoms of an element present in a molecule is known as the atomicity of that element. The atomicity of oxygen in ozone is 3.
Important Points :-
- 1. Water, Air, Stone – all are matter.
- 2. There are primarily three physical states of matter – solid, liquid and gas.
- 3. The information regarding atom was first of all given by Maharshi Kanad.
- 4. Atomism was given by John Dalton.
- 5. Molecules are formed by chemical combination of atoms in a definite proportion.
- 6. Matter is present in the form of element, compound and mixture.
- 7. There are two type of molecules – elemental and compounds.
- 8. Mixture is formed by combining matter in indeterminate or definite proportions.
- 9. Conversion of ice into water is a physical change while breaking of ice molecules into hydrogen (H2 ) and oxygen (O2 ) is a chemical change.
- 10. The matter can be purified by crystallisation, distillation, fractional distillation, differential extraction, filteration etc.
Elements Questions-Answers
Q. 1 When did Maharshi Kanad provided information regarding atom?
(a) 500 BC
(b) 100 BC
(c) 460 BC
(d) 1808 AD
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Answer : – { A }
Q. 2 The atomicity of oxygen in ozone is :
(a) 1
(b) 2
(c) 3
(d) 4
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Answer : – { C }
Q. 3 Which of the following substance is not solid at room temperature ?
(a) Salt
(b) Alum
(c) Oxygen
(d) Sal ammoniac
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Answer : – { C }
Q. 4 The temperature at which liquid changes to solid is known as :
(a) melting point
(b) boiling point
(c) freezing point
(d) condensation temperature
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Answer : – { C }
Q. 5 Which of the following options, is a mixture?
(a) Water
(b) Brass
(c) Iron
(d) Salt
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Answer : – { D }