Explain with examples (i) Atomic number, (ii) Mass number, (iii) Isotopes and (iv) Isobars. Give any two uses of isotopes.

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Solution

(i) Atomic number

The atomic number of an element is the total number of protons present in the atom of that element. For example, nitrogen has 7 protons in its atom. Thus, the atomic number of nitrogen is 7.

(ii) Mass number

The mass number of an element is the sum of the number of protons and neutrons present in the atom of that element. For example, the atom of boron has 5 protons and 6 neutrons. So, the mass number of boron is 5 + 6 = 11.

(iii) Isotopes

Isotopes are atoms of the same element having the same atomic number, but different mass numbers. For example, hydrogen has three isotopes. They are protium, deuterium,and tritium.

(iv) Isobars

Isobars are atoms having the same mass number, but different atomic numbers i.e., isobars are atoms of different elements having the same mass number. For example, andare isobars.

Two uses of isotopes are:

(i) One isotope of uranium is used as a fuel in nuclear reactors.

(ii) One isotope of cobalt is used in the treatment of cancer.

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Q. Question 8
Explain with examples
(i) Atomic number,
(ii) Mass number,
(iii) Isotopes and
(iv) Isobars.
Give any two uses of isotopes.

Q. Match List I with List II and select the correct answer by using the codes given below.
List I List II
A. Isotopes 1. atoms having same atomic number but different mass numbers
B. Isobars 2. atoms with same number of neutrons but different atomic numbers
C. Isotones 3. atoms with same mass number but different atomic numbers

Question 16
Which of the following are the characteristics of isotopes of an element?

(i) Isotopes of an element have same atomic masses
(ii) Isotopes of an element have same atomic number
(iii) Isotopes of an element show same physical properties
(iv) Isotopes of an element show same chemical properties

(a) (i), (iii) and (iv)
(b) (ii), (iii) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)

Q. Explain isotopes and isobars with examples

(a) What are radioactive isotopes ? Give two examples of radioactive isotopes.

(b) Give any two uses of radioactive isotopes.

(c) An element Z contains two naturally occurring isotopes ${}_{17}^{35}Z$ and ${}_{17}^{37}Z$ . If the average atomic mass of this element be 35.5 u, calculate the percentage of two isotopes.

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