Which of the following are true for an element ?
(i) Atomic number = number of protons + number of electrons
(ii) Mass number = number of protons + number of neutrons
(iii) Atomic number = number of protons = number of neutrons
(iv) Atomic number = number of protons = number of electrons

Options

A. (i) and (ii)
B. (i) and (iii)
C. (ii) and (iii)
D. (ii) and (iv)

Explanation

To determine which statements about an element are true, let's analyze each option step by step.

1. **Statement (i): Atomic number = number of protons + number of electrons**
- The atomic number of an element is defined as the number of protons in the nucleus of an atom. The number of electrons in a neutral atom is equal to the number of protons. Therefore, this statement is incorrect because the atomic number does not include electrons in its definition.
- **Conclusion**: This statement is **false**.

2. **Statement (ii): Mass number = number of protons + number of neutrons**
- The mass number of an element is indeed the total count of protons and neutrons in the nucleus. This is a correct definition.
- **Conclusion**: This statement is **true**.

3. **Statement (iii): Atomic number = number of protons = number of neutrons**
- The atomic number is equal to the number of protons, but it is not necessarily equal to the number of neutrons. The number of neutrons can vary in isotopes of the same element. Therefore, this statement is incorrect.
- **Conclusion**: This statement is **false**.

4. **Statement (iv): Atomic number = number of protons = number of electrons**
- In a neutral atom, the number of electrons is equal to the number of protons, which is also the atomic number. Therefore, this statement is correct.
- **Conclusion**: This statement is **true**.

### Final Evaluation:
- The true statements are:
- (ii) Mass number = number of protons + number of neutrons (True)
- (iv) Atomic number = number of protons = number of electrons (True)

### Summary of True Statements:
- (ii) and (iv) are the correct statements.