Question

1) When we move left to right in a period, valency of the elements:
(a) Remains the same (b) Increases
(c) Decreases (d) Increases and then decreases
2. When we move top to bottom in a group, the atomic size of the elements.
(a) Remains the same (b) Increases
(c) Decreases (d) Increases and then decreases
3. When we move left to right in a period the metallic character of elements:
(a) Remains the same (b) Increase
(c) Decrease (d) Increases and then decreases
4. When we move left to right in a period the nuclear charge:
(a) Increases (b) Decreases
(c) Remains the same (d) Increases and then decrease​

Answer 1

• Valency remains same on moving from top to bottom in a particular group. This is because the outermost electronic configuration of all the elements in a group remains same
• Now, as on moving from left to right in a period of periodic table, the nuclear charge increases due to the gradual increase in number of protons, so the valence electrons are pulled more strongly by the nucleus.
• The number of energy levels increases as you move down a group as the number of electrons increases. Each subsequent energy level is further from the nucleus than the last. Therefore, the atomic radius increases as the group and energy levels increase. 2) As you move across a period, atomic radius decreases.
• On the periodic table, electronegativity generally increases as you move from left to right across a period and decreases as you move down a group.