Question

Name any two elements of group one and write their electronic configurations. What similarity do you observe in their electronic configurations? Write the formula of oxide of any of the aforesaid element.(Delhi - 2016)

Answer 1

Group one element

Name of two elements belonging to group 1.

• The names of the elements belonging to group 1 are as follows:

i) Hydrogen

ii) Lithium

iii) Sodium

iv) Potassium

v) Rubidium

vi) Cesium

vii) Francium

Electronic configuration

• The electronic configuration of hydrogen and Lithium is as follows

H - $1s^1$

Li - $1s^22s^1$

• From the above electronic configurations of hydrogen and lithium, it is observed that all elements of group 1 have 1 valence electron.
• It means that the outermost orbital of all group 1 element has one electron.

Formula of oxide

• When group one elements react with oxygen it forms respective oxides as shown below:

Oxide of hydrogen:

$2H_2+O_2\rightarrow2H_2O$

Oxide of Lithium:

$4Li+O_2\rightarrow 2Li_2O$

• Thus the formula of oxide formed by group 1 elements are $H_2O$ and $Li_2O$.

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