Question

1.how does atomic size vary within a horizontal row of the periodic table, explain how this variation arises? ​

Answer 1

Explanation:

On moving from left to right in a period, the atomic size decreases. More and more electrons are added to same shell. The attraction between nucleus and valence electrons increases with increase in the atomic number.

On moving down the group, from top to bottom, the atomic size increases. This is because with increase in the atomic number, extra shells of electrons are added.

Answer 2

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Atomic radius of the elements generally decreases from left to the right in a period because on moving from left to right in a period the nuclear charge gradually increases by one unit and one electron is also added in the electron shell. Due to this the electrons get attracted more and more towards the nucleus consequently the atomic radii decrease.

Atomic radius of the elements increases as we move downwords in a group because on moving down a group there is an increase in principal quantum number and thus, increase in the number of electron shells. Therefore the atomic size is expected to increase.