Question

The atom of an element has electronic configuration 2, 8, 8, 2.
(a) What is the atomic number of the element?
(b) To which of the following elements would it be chemically similar? (Atomic numbers of elements are given in brackets)
He (2); O (8); Mg (12); K (19)
​Give reason for your choice.

Answer 1

Atomic Number of Element is 20

Explanation:

Given,

• Electronic Configuration (2, 8, 8, 2) which makes the Atomic Number as 2 + 8 + 8 + 2 = 20

• Element with Atomic Number 20 is none other then CALCIUM.

B) In the outermost shell of Calcium there are 2 electrons

1. Now the outermost shell of Hydrogen, H has extra 1 Electron (Valency of +1)

2. Oxygen, O has 6 electrons in outermost shell, (Valency is - 2)

3. Magnesium, Mg has 2 electrons in Outermost shell, (Valency is + 2)

4. Potassium, K, having +1 as Valency.

Off these 4 elements only Magnesium has + 2 Valency as Calcium, so it shows the same properties as calcium.

Answer 2

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