If the electronic configuration of `M = 2, 8, 3` and that of `A = 2,8,7 `, the formula of the compound is

Options

A. `M_2A_3`
B. `MA_2`
C. `M_2A`
D. `MA_3`

Explanation

To determine the formula of the compound formed between elements M and A, we will analyze their electronic configurations and deduce their oxidation states.

### Step-by-Step Solution:

1. **Identify the Elements and Their Electronic Configurations**:
- Element M has the electronic configuration `2, 8, 3`.
- Element A has the electronic configuration `2, 8, 7`.

2. **Determine the Valence Electrons**:
- For M: The outermost shell has 3 electrons (the last shell in `2, 8, 3`).
- For A: The outermost shell has 7 electrons (the last shell in `2, 8, 7`).

3. **Determine the Oxidation States**:
- M, having 3 valence electrons, is likely to lose these electrons to achieve a stable electronic configuration. Thus, M will have an oxidation state of +3 (M^3+).
- A, having 7 valence electrons, needs 1 more electron to complete its octet. Therefore, A will gain 1 electron, resulting in an oxidation state of -1 (A^-).

4. **Write the Formula Based on Oxidation States**:
- To combine M and A in a neutral compound, we need to balance the total positive and negative charges.
- M contributes +3 charge, and A contributes -1 charge. To balance this, we need 3 A atoms for every 1 M atom:
- The formula can be derived by cross-multiplying the oxidation states:
- M^3+ requires 3 A^- to balance the charge.
- Therefore, the formula of the compound is M A₃.

5. **Final Answer**:
- The formula of the compound formed between M and A is **MA₃**.