An element L has 9 protons and its valency is 1. Another element M has valency 3 and 5. What is the difference in the number of electrons in L and M?

Options

A. 6
B. 5
C. 4
D. 3

Explanation

To solve the problem, we need to determine the number of electrons in elements L and M, and then find the difference between them.

### Step-by-Step Solution:

1. **Identify Element L:**
- Given that element L has 9 protons.
- The number of protons in an atom is equal to its atomic number. Therefore, the atomic number of L is 9.
- The element with atomic number 9 is Fluorine (F).

2. **Determine the Number of Electrons in L:**
- In a neutral atom, the number of electrons is equal to the number of protons.
- Since L (Fluorine) has 9 protons, it also has 9 electrons.

3. **Identify Element M:**
- Element M has valencies of 3 and 5.
- Elements with these valencies typically belong to group 15 of the periodic table, which includes Nitrogen (N), Phosphorus (P), and Arsenic (As).
- The atomic number of Phosphorus is 15, and that of Arsenic is 33.

4. **Determine the Number of Electrons in M:**
- For Phosphorus (atomic number 15), the number of electrons is also 15 (since it is neutral).
- For Arsenic (atomic number 33), the number of electrons is 33.

5. **Calculate the Difference in Number of Electrons:**
- If we consider Phosphorus (M):
- Number of electrons in L (Fluorine) = 9
- Number of electrons in M (Phosphorus) = 15
- Difference = 15 - 9 = 6
- If we consider Arsenic (M):
- Number of electrons in M (Arsenic) = 33
- Difference = 33 - 9 = 24

6. **Conclusion:**
- The question asks for the difference in the number of electrons in L and M. If we take M as Phosphorus, the difference is 6. If we take M as Arsenic, the difference is 24. However, since the question seems to focus on the common valency of 3 and 5, we will consider Phosphorus as M.
- Therefore, the difference in the number of electrons between L and M (Phosphorus) is **6**.

### Final Answer:
The difference in the number of electrons in L (Fluorine) and M (Phosphorus) is **6**.

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