JEE Chemistry 2025 Question with Solution

Given: Five statements A to E about the periodic table are given.

Find: Which statements are NOT true according to the modern periodic table.

Evaluate each statement using the modern periodic law.

1. Statement A: The properties of elements are a function of atomic weights.

This is not true for the modern periodic table. The modern periodic law states that the properties of elements are a periodic function of their atomic numbers, not atomic weights.

2. Statement B: The properties of elements are a function of atomic numbers.

This is true. This is exactly the basis of the modern periodic table.

3. Statement C: Elements having similar outer electronic configuration are arranged in the same period.

This is not true. Elements with similar outer electronic configuration are arranged in the same group, not the same period.

4. Statement D: An element's location reflects the quantum numbers of the last filled orbital.

This is true. The position of an element is related to the nature of the last filled orbital.

5. Statement E: The number of elements in a period is the same as the number of atomic orbitals available in the energy level that is being filled.

This is not true. The number of elements in a period corresponds to the number of electrons that can be accommodated during filling, not merely the number of atomic orbitals.

Therefore, the statements that are NOT true are A, C, and E. Hence, the correct option is A.

Given: Statements A to E about the periodic table.

Find: The incorrect statements.

Hint used: Elements in the same period have the same principal quantum number, while elements in the same group have similar outer electronic configuration. The modern periodic table is based on atomic number.

For E, check with examples:

• First period has 2 elements due to filling of $1s$.
• Second period has 8 elements due to filling of $2s$ and $2p$.

So the number of elements in a period matches electron capacity of the relevant subshells being filled, not just the number of orbitals counted in the stated way. Hence E is false.

Thus, false statements are A, C, and E. The correct option is A.