Online test of Chapter 4 Structure of Atom 1 Science| Class 9th

Questions:
1. The four atomic species can be represented as follows. Out of these, the two species which can be termed isobars are:
(i) ²⁰¹X₆₀ (ii) ²⁰⁰X₆₁ (iii) ²⁰⁰X₅₈ (iv) ²⁰³X₆₀
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (i) and (iv)

2. An element has electronic configuration 2, 6; the element is
(a) Carbon
(b) Nitrogen
(c) Oxygen
(d) Fluorine

3. The radioactive isotope used in the treatment of cancer is:
(a) plutonium-239
(b) arsenic-74
(c) cobalt-60
(d) iodine-131

4. The atomic number of an element X is 8 and that of element Y is 4. Both these elements can exhibit a valency of:
(a) 1
(b) 2
(c) 3
(d) 4

5. The number of valence electrons in Mg are
(a) 1
(b) 2
(c) 3
(d) 4

6. Elements having valency ‘one’ are:
(a) always metals
(b) always non-metals
(c) always metalloids
(d) either metals or non-metals

7. Which of the following has one valence electron
(a) Li
(b) Ca
(c) Mg
(d) Be

8. Mass number of calcium is ………, if it has 20 electrons and 20 neutrons.
(a) 40
b) 20
(c) 18
(d) 30

9. In Rutherford’s Gold foil experiment most of rays passed through atom showing that
(a) most of the atom is hollow
(b) atoms is +vely charged at the centre
(c) atom is spherical
(d) atom is neutral

10. Which of the following elements does not exhibit electrovalency ?
(a) calcium
(b) chromium
(c) carbon
(d) cadmium

11. The valency of oxygen with atomic number 8 is
(a) 6
(b) 2
(c) 4
(d) 1