An element 'X' has mass number 40 and contains 21 neutrons in its atom. To which group of the periodic table does it belong.

Options

A. group1
B. group 2
C. group 17
D. group 13

Explanation

To solve the problem, we need to determine the group of the periodic table to which element 'X' belongs, given its mass number and the number of neutrons.

### Step-by-Step Solution:

1. **Identify the Given Information:**
- Mass number of element 'X' = 40
- Number of neutrons in element 'X' = 21

2. **Calculate the Atomic Number:**
- The atomic number (Z) can be calculated using the formula:
\[ \text{Atomic Number} = \text{Mass Number} - \text{Number of Neutrons} \]
- Substituting the given values:
\[ Z = 40 - 21 = 19 \]

3. **Identify the Element:**
- The atomic number 19 corresponds to the element Potassium (K).

4. **Determine the Group of the Element:**
- Potassium (K) is located in Group 1 of the periodic table, which is known as the alkali metals group.

5. **Conclusion:**
- Therefore, element 'X' belongs to Group 1 of the periodic table.

### Final Answer:
Element 'X' belongs to Group 1 of the periodic table.

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