ICSE Class 10 Chemistry
Question 7 of 25
Periodic Table, Periodic Properties and Variations of Properties — Question 17
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Question Assertion (A): Second period consists of 8 elements.
Reason (R): Number of elements in each period is four times the number of atomic orbitals available in energy level that is being filled.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
A is true but R is false.
Explanation — The second period includes the elements from lithium (Z=3) to neon (Z=10): Li, Be, B, C, N, O, F, Ne → 8 elements. Hence assertion is true. Reason given is incorrect. In the first period, electrons are being added to the K electronic configuration.
The number of available electronic configuration or orbital for elements of first period is 1.
The number of elements present in the first period is 2, which is not four times the number of atomic orbitals available. Hence the (R) statement is false.