Which statement is TRUE?
An atom of Carbon-14 contains 6 protons, 8 neutrons, 6 electrons in its nucleus.
An atom of Bromine-79 contains 79 protons, 44 neutrons, 35 electrons.
lons are formed by changing the number of protons in an atom’s nucleus.
1602- has 10 electrons.
The number of protons and neutrons is always the same in the neutral atom.
The correct answer and explanation is :
The correct statement is:
( \text{O}^{2-} ) has 10 electrons.
Explanation:
- Why is ( \text{O}^{2-} ) having 10 electrons correct?
- The element oxygen (O) has an atomic number of 8, meaning a neutral oxygen atom has 8 protons and 8 electrons.
- The ( O^{2-} ) ion means the oxygen atom has gained 2 extra electrons to form a stable octet configuration.
- Thus, the total number of electrons in ( O^{2-} ) is 8 + 2 = 10.
- Why are the other statements incorrect?
- “An atom of Carbon-14 contains 6 protons, 8 neutrons, 6 electrons in its nucleus.”
- Incorrect: Carbon-14 (( ^{14}C )) has 6 protons and 8 neutrons, but electrons are not found in the nucleus; they orbit the nucleus.
- “An atom of Bromine-79 contains 79 protons, 44 neutrons, 35 electrons.”
- Incorrect: Bromine (( ^{79}Br )) has an atomic number of 35, meaning it has 35 protons (not 79).
- Its mass number is 79, so the number of neutrons is 79 – 35 = 44, which is correct.
- However, the incorrect proton count makes the whole statement false.
- “Ions are formed by changing the number of protons in an atom’s nucleus.”
- Incorrect: Ions are formed by gaining or losing electrons, not by changing the number of protons.
- Changing the proton number would result in a completely different element, not just an ion.
- “The number of protons and neutrons is always the same in a neutral atom.”
- Incorrect: While protons always remain the same for a given element, neutrons can vary (e.g., isotopes like Carbon-12 and Carbon-14 have different neutron counts).
Thus, ( O^{2-} ) having 10 electrons is the only true statement.