Dr. Parul Srivastava Solutions for Chapter: Periodic Classification of Elements, Exercise 4: Check Your Progress

Two elements $\mathrm{X}$ and $\mathrm{Y}$ have atomic numbers $12$ and $16$ respectively. Write the electronic configuration for these elements. To which period of the modern periodic table do these two elements belong? What type of bond will be formed between them and Why?

Tendency to lose electrons decreases as we move from left to right in a period. Why?

Tendency to lose electrons increases as we move from top to bottom in a group. Why?

Atomic number is considered a more appropriate parameter than atomic mass for classification of elements in a periodic table. Why? How does atomic size of elements vary on moving from (i) left to right in a period (ii) from top to bottom in a group. Give reasons for your answer.

Though the atomic mass of cobalt ($58.9$) is greater than nickel ($58.7$), yet $\mathrm{Co}$ is placed before $\mathrm{Ni}$ in Mendeleev's periodic table. Why?