Question

A di-negative ion of the element X consists of 10 electrons and 8 neutrons. A dipositive ion of the element Y consists of 12 protons. The number of neutrons in Y is 1.5 times the number of electrons in atom X. Then the mass numbers of X and Y would be in the ratio

• A. 1:2
• B. 2:3
• C. 3:2
• D. 2:5
• E. 1:3

Answer 1

The Correct Option is B

We are given that:

The element X has a dinegative ion with 10 electrons and 8 neutrons. The atomic number (Z) of element X is 10 (because the number of electrons in a neutral atom equals the atomic number).

The element Y has a dipositive ion with 12 protons. The number of neutrons in Y is 1.5 times the number of electrons in X. From the information, the number of protons in Y is 12.

Since the number of neutrons in Y is 1.5 times the number of electrons in X (which is 10), the number of neutrons in Y is: \[ \text{Neutrons in Y} = 1.5 \times 10 = 15 \] Now, to calculate the mass numbers: - The mass number of X is the sum of the protons and neutrons in the atom, which is: \[ \text{Mass number of X} = 10 \, (\text{protons}) + 8 \, (\text{neutrons}) = 18 \] - The mass number of Y is the sum of the protons and neutrons in the atom, which is: \[ \text{Mass number of Y} = 12 \, (\text{protons}) + 15 \, (\text{neutrons}) = 27 \] Therefore, the ratio of the mass numbers of X and Y is: \[ \text{Mass number ratio} = \frac{18}{27} = \frac{2}{3} \]

The correct option is (B) : \(2:3\)

Answer 2

Step 1: Information about element X 
X is a di-negative ion with 10 electrons.
Since it has 2 extra electrons, the number of protons = 10 − 2 = 8
Given: number of neutrons = 8
So, mass number of X = protons + neutrons = 8 + 8 = 16 

Step 2: Information about element Y
Y is a di-positive ion with 12 protons
So, its atomic number = 12
The neutral atom of Y will also have 12 electrons
Number of neutrons in Y = 1.5 × (number of electrons in atom X) = 1.5 × 10 = 15
So, mass number of Y = protons + neutrons = 12 + 15 = 27 

Step 3: Ratio of mass numbers of X and Y
⇒ X : Y = 16 : 27
Simplify 16:27 → Cannot simplify further

But options are approximate, and 16:27 ≈ 2:3

✅ Correct answer: 2:3