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The Fundamental Unit of Life
Explain with examples, (i) Atomic number, (ii) Mass number, (iii) Isotopes, and (iv) Isobars. Give any two uses of isotopes also.
(i) Atomic number is defined as number of protons present in the nucleus of an atom. For example, there are 6 protons in carbon, so the atomic number of carbon is 6. All atoms are characterized by their atomic numbers.
(ii) Mass number is defined as the sum of the total number of protons and neutrons present in the nucleus of an atom. For example there are 6 protons and 6 neutrons in the nucleus of carbon, so its mass number is 12.
(iii) Isotopes are atoms of the same element thus having same atomic number but different mass number. For example, chlorine has two isotopes with atomic number 17 but mass numbers as 35 and 37.
(iv) Isobars are such atoms which have same mass number but different atomic numbers. Thus isobars are different elements. For example, Ne has atomic number as 10 and sodium has atomic number as 11 but both of these have mass numbers as 22.
Uses of Isotopes
(i) Isotope of cobalt, ( Co), is used in the treatment of cancer.
(ii) Isotope of uranium (235U) is used as a fuel in nuclear reactors.
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Na+ has completely filled K and L-shells. Explain.
If Z = 3, what would be the valency of the element? Also, name the element.
Composition of the nuclei of two atomic species X and Y are given as under
X Y
Protons = 6 6
Neutrons= 6 6
Give the mass numbers of X and Y. What is the relation between the two species?
For the following statements, write T for True and F for False.
(a) J.J. Thomson proposed that the nucleus of an atom contains only nucleons.
(b) A neutron is formed by an electron and a proton combining together. Therefore, it is neutral.
(c) The mass of an electron is about 1/2000 times that of proton.
(d) An isotope of iodine is used for making tincture iodine, which is used as a medicine.
Rutherford’s α-particle scattering experiment was responsible for the discovery of
Isotope of an element has
Number of valence electrons in Cl- ion are
Which one of the following is a correct ? Electronic configuration of sodium
(a) 2, 8,2 (b) 8, 2, 1 (c) 2, 1, 8 (d) 2, 8, 1.
Complete the following Table:
|
Atomic number |
Mass number |
Number of neutrons |
Number of protons |
Number of electrons |
Name of the atomic species |
|
9 |
- |
10 |
- |
- |
- |
|
16 |
32 |
- |
- |
- |
Sulphur |
|
- |
24 |
- |
12 |
- |
- |
|
- |
2 |
- |
1 |
- |
- |
|
- |
1 |
- |
1 |
0 |
- |
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