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The Fundamental Unit Of Life

Question
CBSEENSC9005126
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Summarize the rules for writing of distribution of electrons in various shells for the first eighteen elements.

Solution

Following rules are followed to fill electrons in different energy levels,

(i) If n gives the number of orbit or energy level, then 2n2 gives the maximum number of electrons possible in a given orbit or energy level. Thus

First orbit or K-shell will have 2n2 =2 x 1 = 2 electrons

Second orbit or L-shell will have 2n2 = 2 x 22 =8 electrons

Third orbit or M-shell will have 2n2 = 2 x 23 =18 electrons

(ii) If it is the outermost orbit, then it should have not more than 8 electrons.

(iii) There should be stepwise filling of electrons in different orbits, i.e., electrons are not accommodated in a given orbit if the earlier orbits or shells are incompletely filled.

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Some More Questions From The Fundamental Unit of Life Chapter

Define valency by taking examples of silicon and oxygen.

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

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

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