Question

The size of metal atoms 1 generally increases progressively from top to bottom in a group in the periodic table. 2) generally increases progressively from left to right in a period. 3) are smaller than those of the corresponding ions. O4) do not change upon losing electrons.

Answer 1

The correct answer is option 1.

Explanation:

Option 1: While going from top to bottom in a group, one shell is added for each period while the number of valence electrons remain same.This addition of shell is the primary reason for the significant increase in radius of atoms in most cases. Though there is an increase in the overall nuclear charge, the outer electrons are shielded from it by the fully filled inner orbitals and effective nuclear charge does not increase as much as to create a reduction in size.

Option 2: The size actually decreases from left to right in a period except for the group 18 elements. Within a period, protons are added to the nucleus as electrons are being added to the same shell or principal energy level. These electrons are gradually pulled closer to the nucleus because of its increased positive charge. Since the force of attraction between nuclei and electrons increases, the size of the atoms decreases. This effect outweighs the repulsive force between the electrons being added by a large margin. However group 18 elements do not follow this trend because they are measured in terms of their van der wals radius whereas all other elements are measured in terms of covalent or metallic radius.

Option 3: Size of metal atoms is actually larger than their ions which are basically cations. Metals form ions by losing electrons when the number of protons remains constant. Thus the effective nuclear charge increases, pulling the electrons closer and the inter-electronic repulsion also decreases. Both these factors contribute to the decrease in size of the ions.

Option 4: As discussed for option 3, the size of atom does change upon losing electrons, the size decreases. As an electron is removed, the effective nuclear charge on each electron increases and inter-electronic repulsion decreases. So, electrons are pulled closer to the nucleus and size decreases.