The electronic configuration of four elements `L, P, Q` and `R` are given in brackets
`L (1s^(2), 2s^(2), 2p^(4)) , P (1s^(2), 2p^(6), 3s^(1))`
`Q (1s^(2), 2s^(2)2p^(6), 3s^(2)3p^(5)) , R (1s^(2), 2s^(2)2p^(6), 3s^(2))`
The formula of ionic compounds that can be formed between elements are

Options

A. `L_2 P, RL, PQ, R_2Q`
B. `LP , L , PQ, RQ `
C. `P_2 L , RL, PQ, RQ_2`
D. `LP, R_2 L, P_2 Q, RQ `

Answer

To determine the formulas of ionic compounds that can be formed between the elements L, P, Q, and R based on their electronic configurations, we first need to identify the valencies of each element. The valency is the number of electrons an atom can lose, gain, or share to achieve a full outer shell (octet).

### Step-by-Step Solution:

1. **Identify the Electronic Configurations:**
- L: \(1s^2, 2s^2, 2p^4\)
- P: \(1s^2, 2p^6, 3s^1\)
- Q: \(1s^2, 2s^2, 2p^6, 3s^2, 3p^5\)
- R: \(1s^2, 2s^2, 2p^6, 3s^2\)

2. **Determine the Valency of Each Element:**
- **Element L:**
- Configuration: \(2s^2, 2p^4\) (total of 6 electrons in the outer shell)
- Needs 2 more electrons to complete the octet.
- **Valency = 2** (gains 2 electrons)

- **Element P:**
- Configuration: \(3s^1\) (total of 1 electron in the outer shell)
- Can lose 1 electron to complete the octet.
- **Valency = 1** (loses 1 electron)

- **Element Q:**
- Configuration: \(3s^2, 3p^5\) (total of 7 electrons in the outer shell)
- Needs 1 more electron to complete the octet.
- **Valency = 1** (gains 1 electron)

- **Element R:**
- Configuration: \(3s^2\) (total of 2 electrons in the outer shell)
- Can lose 2 electrons to complete the octet.
- **Valency = 2** (loses 2 electrons)

3. **Formulate Ionic Compounds:**
- **L and P:**
- L (valency 2) and P (valency 1) can form \(LP_2\).

- **L and Q:**
- L (valency 2) and Q (valency 1) can form \(LQ_2\).

- **P and Q:**
- P (valency 1) and Q (valency 1) can form \(PQ\).

- **R and L:**
- R (valency 2) and L (valency 2) can form \(RL\) or \(R_2L_2\) which simplifies to \(RL\).

- **R and Q:**
- R (valency 2) and Q (valency 1) can form \(RQ_2\).

### Summary of Ionic Compounds:
- \(LP_2\)
- \(LQ_2\)
- \(PQ\)
- \(RL\)
- \(RQ_2\)