Atomic Structure

Samacheer Book Back Questions And Answers For Science Standard 8 “Atomic Structure“

I. Choose the best answer:
1. The same proportion of carbon and oxygen in the carbon dioxide obtained from different sources proves the law of _____.
a) reciprocal proportion
b) definite proportion
c) multiple proportion
d) conservation of mass

2. Cathode rays are made up of _____.
a) neutral particles
b) positively charged particles
c) negatively charged particles
d) None of the above

3. In water, hydrogen and oxygen are combined in the ratio of _____ by mass.
a) 1:8
b) 8:1
c) 2:3
d) 1:3

4. Which of the following statements made by Dalton has not undergone any change?
a) Atoms cannot be broken.
b) Atoms combine in small, whole numbers to form compounds.
c) Elements are made up of atoms.
d) All atoms of an elements are alike

5. In all atoms of an element
a) the atomic and the mass number are same.
b) the mass number is same and the atomic number is different.
c) the atomic number is same and the mass number is different
d) both atomic and mass numbers may vary.

II. Fill in the blanks:
1. Atom is the smallest particle of an element.
2. An element is composed of same kind of atoms.
3. An atom is made up of proton, electron and neutron.
4. A negatively charged ion is called anion, while positively charged ion is called cation.
5. Electron is a negatively charged particle (Electron/Proton).
6. Proton is deflected towards the negatively charged plate (positively, negatively).

III. Match the following:
1. Law of conservation of mass     A. Sir William Crookes
2. Law of constant proportion       B. James Chadwick
3. Cathode rays                              C. Joseph Proust
4. Anode rays                                 D. Lavoisier
5. Neutrons                                    E. Goldstein

Answers:
1. D
2. C
3. A
4. E
5. B

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