`overset20 8X` atom is isotonic to `oversety 10Y` atom. The value of y is :

Options

A. 12
B. 22
C. 10
D. 8

Explanation

To solve the problem, we need to determine the value of \( y \) for the atom \( \overset{y}{10Y} \) that is isotonic to the atom \( \overset{20}{8X} \). Here are the steps to find the solution:

### Step 1: Understand the concept of isotonic atoms
Isotonic atoms are atoms that have the same number of neutrons. To find the number of neutrons in an atom, we use the formula:
\[ \text{Number of Neutrons} = A - Z \]
where \( A \) is the atomic mass and \( Z \) is the atomic number.

### Step 2: Calculate the number of neutrons in atom \( X \)
For the atom \( \overset{20}{8X} \):
- Atomic mass \( A = 20 \)
- Atomic number \( Z = 8 \)

Using the formula:
\[ \text{Number of Neutrons in } X = 20 - 8 = 12 \]

### Step 3: Set up the equation for atom \( Y \)
For the atom \( \overset{y}{10Y} \):
- Atomic mass \( A = y \)
- Atomic number \( Z = 10 \)

Using the same formula for the number of neutrons:
\[ \text{Number of Neutrons in } Y = y - 10 \]

### Step 4: Set the number of neutrons equal
Since \( X \) and \( Y \) are isotonic, their number of neutrons must be equal:
\[ 20 - 8 = y - 10 \]
This simplifies to:
\[ 12 = y - 10 \]

### Step 5: Solve for \( y \)
To find \( y \), we can rearrange the equation:
\[ y = 12 + 10 = 22 \]

### Conclusion
The value of \( y \) is \( 22 \).