The ratio of isotopes of Cl 17 37 , and Cl 17 35 in natural chlorine is 1:3. Calculate the fractional atomic mass of chlorine.

Atomic mass of 1 atom of Cl = 37 x 1 = 37 u. Atomic mass of 3 atoms of Cl = 35 x 3 = 105 u. Atomic mass of 4 atoms of natural chlorine = (37 + 105) = 142 u Therefore, Average atomic mass of natural chlorine = 142 4 amu = 35.5 u

E M B I B E

Core science chemistry>Chapter 4 - Structure of Atom>EXERCISE 4B>Q 8

EASY

9th CBSE

IMPORTANT

Earn 100

Helium atom has 2 electrons in its valence shell but its valency is not 2. Explain.

Important Questions on Structure of Atom

EASY

9th CBSE

IMPORTANT

Core science chemistry>Chapter 4 - Structure of Atom>EXERCISE 4B>Q 9

An element X has a mass number 4 and atomic number 2. Write the valency of this element.

EASY

9th CBSE

IMPORTANT

Core science chemistry>Chapter 4 - Structure of Atom>EXERCISE 4B>Q 10

The atomic number of calcium and argon are 20 and 18 respectively, but the mass number of both these elements is 40. What is the name given to such a pair of elements?

EASY

9th CBSE

IMPORTANT

Core science chemistry>Chapter 4 - Structure of Atom>EXERCISE 4B>Q 1

Name two elements, which have octet structure.

HARD

9th CBSE

IMPORTANT

Core science chemistry>Chapter 4 - Structure of Atom>EXERCISE 4B>Q 2

What is the valency of the following elements?
(i) Hydrogen (atomic no. 1)
(ii) Magnesium (atomic no. 12)
(iii) Fluorine (atomic no. 9)
(iv) Sulphur (atomic no. 16)

EASY

9th CBSE

IMPORTANT

Core science chemistry>Chapter 4 - Structure of Atom>EXERCISE 4B>Q 3

Give one similarity and one difference between the isotopes