Question

Assertion: Elements placed in a group are chemically similar.

Reason: Elements placed in a group have same valence shell electronic configuration of their elements.

Mark the correct choice as,

• A. Both assertion and reason are true and the reason is the correct explanation of assertion.
• B. Both assertion and reason are true but the reason is not the correct explanation of assertion.
• C. Assertion is true but the reason is false.
• D. Both assertion and reason are false

Answer 1

The correct option is A

Both assertion and reason are true and the reason is the correct explanation of assertion.

Explanation for Assertion statement:

1. Elements from the same group have the same chemical behaviour. For example, elements of group 1, known as alkali metals have the same chemical properties.
2. All of them are very reactive and are not found in the free state.
3. They all form Ionic compounds (compounds formed by the complete transfer of electrons).
4. They all react violently with water or dilute acids to form hydrogen. Etc.

Explanation for the reason statement:

1. All the elements in a group have the same valence shell electronic configuration, because of this, they have the same chemical behaviour. For example, group 1 has the electronic configuration of

$$\begin{gathered} {}_{3}Li=2,1 \\ {}_{11}Na=2,8,1 \\ {}_{19}K=2,8,8,1 \end{gathered}$$

${}_{37}Rb=2,8,18,8,1$etc.

2. All of them here have 1 electron in their outermost shell.

Hence, A) Both assertion and reason are true, reason is the correct explanation of assertion.