An element X, in which the difference in electrons present in valence shell (M shell) and penultimate shell is equal to the number of electrons present in the first shell, undergoes combustion to produce Y. Y turns lime water milky due to the formation of Z. Identify X, Y and Z.

Options

A. `C, CO_2, CaCO_3`
B. `S, SO_2, CaSO_3`
C. `S, SO_2 , Ca(HSO_3)_2`
D. `C, CO_2, Ca(HCO_3)_2`

Explanation

To solve the problem step by step, let's analyze the information given in the question:

### Step 1: Determine the number of electrons in the shells
We know that:
- The difference in the number of electrons in the valence shell (M shell) and the penultimate shell (L shell) is equal to the number of electrons in the first shell (K shell).
- The first shell (K shell) has 2 electrons.

Let:
- Number of electrons in the K shell = 2
- Number of electrons in the L shell = 8 (fully filled)
- Let the number of electrons in the M shell = x

According to the problem:
\[ x - 8 = 2 \]
This means:
\[ x = 2 + 8 = 10 \]

### Step 2: Identify the element X
Now we have the electron configuration:
- K shell = 2
- L shell = 8
- M shell = 10

The total number of electrons (which is the atomic number) is:
\[ 2 + 8 + 10 = 20 \]

The element with atomic number 16 is Sulfur (S). Therefore, X is Sulfur.

### Step 3: Determine the combustion product Y
When sulfur (X) undergoes combustion in the presence of oxygen, it forms sulfur dioxide (SO2). Thus, Y is SO2.

### Step 4: Identify the compound Z
The problem states that Y (SO2) turns lime water milky. Lime water is a solution of calcium hydroxide (Ca(OH)2). When sulfur dioxide reacts with lime water, it forms calcium sulfite (CaSO3), which is a white precipitate that makes the lime water appear milky. Therefore, Z is CaSO3.

### Final Answer
- X = Sulfur (S)
- Y = Sulfur Dioxide (SO2)
- Z = Calcium Sulfite (CaSO3)