Question

​The diagram below shows the first three periods of the modern periodic table. Three elements have been represented by the letters X1, X2, and X3. ​

Arrange these elements in decreasing order of their valency.​

• A. $X_3>X_2>{X_1}^{}$
• B. $X_3>X_2>{X_1}^{}$
• C. $X_1>{X_2}^{}>{X_3}^{}$
• D. $X_1>X_3>{X_2}^{}$

Answer 1

The correct option is D $X_1>X_3>{X_2}^{}$

Let’s analyse the periodic table to guess the exact elements present in the given group and period.
On comparing these two, we can see that the given elements are;
X1: Carbon
X2: Fluorine
X3: Magnesium

• Valency remains the same down the group.​
• Valency first increases till 4 and then decreases to 0 on going from left to right in a period.

So, the correct answer is option D.