Question

An element x' has atomic no. 35. Name the
group and period to which the element
belongs? what would be the nature of the
oxide of element '? (2)​

Answer 1

Answer:

The atomic number of the element X is 17. It belongs to group 17 and period 3. Valency of this is 1.

Explanation:

Atomic number is defined as the number of protons or number of electrons that are present in neutral atom.

Atomic number = Number of protons = Number of electrons

Mass number is defined as the sum of number of protons and number of neutrons.

Mass number = Number of protons + Number of neutrons

We are given:

Mass number of X = 35

Number of neutrons = 18

Number of protons or atomic number = 35 - 18 = 17

Electronic configuration of element X = 1s^22s^22p^63s^23p^51s

2

2s

2

2p

6

3s

2

3p

5

To identify the period, we look at the highest occupied principle quantum number which is 'n'. Here, the value of 'n' is 3. Thus, it belongs to Period 3 of the periodic table.

As, the last electron in entering p-shell. Thus, it is a p-block element.

The rule for determining the group number for p-block element is:

Group number = Number of valence electrons + 10

The number of valance electrons = 2 + 5 = 7

Group number = 7 + 10 = 17

Thus, it belongs to Group 17.

This element requires one electron to obtain stable electronic configuration. So, its valency is 1.

Hence, the atomic number of the element X is 17. It belongs to group 17 and period 3. Valency of this is 1.