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The Fundamental Unit Of Life

Question
CBSEENSC9005219
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What are valence electrons?

Give two examples to illustrate the answer.

Solution

The number of electrons present in the outermost shell of an atom are known as valence electrons.

Examples:

Element

No. of Electrons

Electronic Configuration

Valence Electrons

Boron

5

K=2,L= 3

3

Oxygen

8

K=2,L= 6

6

From the above table, in case of boron there is 3 electron present in outermost shell therefore valence electron for boron is 3. In the same manner, oxygen have 6 electron in its outer most shell, hence it have 6 valence electron.

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Some More Questions From The Fundamental Unit of Life Chapter

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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