Which of the following statement is always correct?

Options

A. An atom has equal number of electrons and protons
B. An atom has equal number of electrons and neutrons
C. An atom has equal number of protons and neutrons
D. An atom has equal number of electrons, protons and neutrons

Explanation

To determine which statement is always correct regarding atoms, let's analyze each statement step by step:

1. **Statement 1: An atom has equal number of electrons and protons.**
- This statement is true for neutral atoms. In a neutral atom, the number of negatively charged electrons equals the number of positively charged protons, resulting in no overall charge. Therefore, this statement is correct.

2. **Statement 2: An atom has equal number of electrons and neutrons.**
- This statement is not always true. While some isotopes of elements may have equal numbers of electrons and neutrons, this is not a general rule for all atoms. The number of neutrons can vary, especially in isotopes.

3. **Statement 3: An atom has equal number of protons and neutrons.**
- This statement is also not always true. The number of protons (which defines the element) and the number of neutrons can vary. For example, carbon has 6 protons and can have 6, 7, or 8 neutrons in its isotopes.

4. **Statement 4: An atom has equal number of electrons, protons, and neutrons.**
- This statement is incorrect. While some isotopes may have equal numbers of protons and neutrons, it is not a universal truth. Most atoms do not have equal numbers of all three subatomic particles.

5. **Statement 5: An atom is electrically neutral.**
- This statement is generally true for neutral atoms. However, it does not specify the condition under which this is true (i.e., that the number of electrons equals the number of protons). Therefore, while it is correct, it does not directly answer the question about equality among subatomic particles.

**Conclusion:**
The statement that is always correct is: **An atom has equal number of electrons and protons.**