The Fundamental Unit of Life
State the suggestions made by Bohr and Bury with regard to distribution of electrons in different energy levels in the atoms of elements.
Or
Explain the arrangement of electrons outside the nucleus.
(i) Electrons are revolving around the nucleus in different orbits or shells. These energy shells are represented by numbers 1, 2, 3, 4 or K, L, M, N.
(ii) The maximum number of electrons in any shell cannot exceed 2n2 , where n is the number of that energy level. Thus for
K-shell, n = 1, no. of electrons = 2x12 =2
L-shell, n = 2, no. of electrons = 2x22 =8
M-shell, n = 3, no. of electrons = 2x32 =18
N-shell, n = 4, no. of electrons = 2x42 = 32.
(iii) The outermost orbit of an atom cannot have more than 8 electrons and the next to the outermost shell (penultimate shell) can have at the most 18 electrons.
(iv) It is not necessary that an orbit has its full quota of electrons before starting to fill the next higher orbit.
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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 |
- |
How do you establish that matter is electrical in nature?
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