Question

gradation in properties first valency second atomic number third metallic and fourth non metallic properties​

Answer 1

A)sodium (argon also ) b) argon d)fluorine

Answer 2

Dear student,

● Gradation of properties in modern periodic table -
a) Valency -
- Across a period, valency first increases and then decreases.
- Down the group valency remains same.

b) Atomic number -
- Across the period as well as down the group atomic number increases.

c) Metallic properties -
- Along a period, metallic character decreases.
- Down a group, metallic character increases.

d) Non-metallic properties -
- Along a period, non-metallic character increases.
- Down a group, non-metallic character decreases.

Hope this helped...