Question

An element has its electronic configuration as 2,8,3.
Now answer the following questions:
(a) What is the atomic number of this element?
(b) State the group number of this element
To which period does this element belong?
(c)​

Answer 1

Answer:

The atomic number of this element is 12 . It belongs to II group and 3 period. The resemble element is Be.

Explanation:

Given that,

The configuration = 2,8,2

(a). The atomic number of this element :

The electronic configuration = 2,8,2

2,8,2=1s^2,2s^2\ 2p^6,3s^22,8,2=1s

2

,2s

2

2p

6

,3s

2

This element is Mg.

Therefore, The atomic number of this element is 12.

(b). The group of this element is second group because the last electron enters to s block.

Thus it is a s block element. For s block elements the group no is equal to the no of electrons the valence shell contains

(c). The element belongs to 3rd period because the last electron enters into the third energy level.

(d). Be is the resemble element of this element because the last electron is same in the electronic configuration.

The electronic configuration of Mg = 2,8,2

The electronic configuration of Be = 2,2

Hence, The atomic number of this element is 12 . It belongs to II group and 3 period. The resemble element is Be.

Answer 2

Given:

The electronic configuration of an element.

To find:

The atomic number of the element.

The group number of the element.

The period to which this belongs.

Solution:

The electronic configuration is given as 2,8,3, i.e., K shell consists of 2 electrons, L shell consists of 8 electrons and M shell consists of 3 electrons.

To determine the atomic number of this element, add the no. of electrons in each shell.

(a) Atomic number = No. of electrons in K shell + No. of electrons in L shell + No. of electrons in M shell

Atomic number = 2 + 8 + 3

Atomic number = 13

The element having atomic number 13 is Aluminum.

(b) Here, the third shell can accommodate a maximum of 8 electrons. But only 3 electrons are present in this shell, which is the outer shell. Hence, the no. of valence electrons in this shell is 3. The group having 3 valence electrons is the Boron group, which is group 13. Hence, the group number of Aluminum is 13.

(c) The valence electrons are present in the third shell. Hence, the period is 3.

The atomic number of this element is 13 having a group number and period number as 13 and 3 respectively. The element is Aluminum.