Which of the following set(s) consist of only isoelectronic species? 

Options

A. `N^(3-), O^(2-), N e , Na^(+)`
B. `NO_(3)^(-), SiO_(4)^(4-) , CO_(3)^(2-)`
C. `Hg^(2+), Pb^(4+)`
D. `H,He^(+), Li^(2+), Be^(3+)`

Answer

To determine which sets consist of only isoelectronic species, we need to analyze each species in the sets given and count their total number of electrons. Isoelectronic species are those that have the same number of electrons.

### Step-by-Step Solution:

1. **Understanding Isoelectronic Species**:
- Isoelectronic species have the same number of electrons. For example, if one atom has 10 electrons and another species also has 10 electrons, they are isoelectronic.

2. **Analyzing the First Set**:
- **Nitrogen (N)**: Atomic number = 7, electrons = 7. If it gains 3 electrons (N³⁻), it has 10 electrons.
- **Oxygen (O)**: Atomic number = 8, electrons = 8. If it gains 2 electrons (O²⁻), it has 10 electrons.
- **Neon (Ne)**: Atomic number = 10, electrons = 10.
- **Sodium (Na)**: Atomic number = 11, electrons = 11. If it loses 1 electron (Na⁺), it has 10 electrons.
- **Conclusion for Set 1**: All species have 10 electrons. Therefore, Set 1 consists of isoelectronic species.

3. **Analyzing the Second Set**:
- **Nitrate ion (NO₃⁻)**: Nitrogen = 7 electrons, Oxygen = 8 electrons (3 O atoms = 24 electrons). Total = 7 + 24 + 1 (for the negative charge) = 32 electrons.
- **Silicate ion (SiO₄²⁻)**: Silicon = 14 electrons, Oxygen = 8 electrons (4 O atoms = 32 electrons). Total = 14 + 32 + 2 (for the negative charge) = 48 electrons.
- **Carbonate ion (CO₃²⁻)**: Carbon = 6 electrons, Oxygen = 8 electrons (3 O atoms = 24 electrons). Total = 6 + 24 + 2 (for the negative charge) = 32 electrons.
- **Conclusion for Set 2**: The total number of electrons for NO₃⁻ and CO₃²⁻ is 32, but SiO₄²⁻ has 48 electrons. Therefore, Set 2 does not consist of isoelectronic species.

4. **Analyzing the Third Set**:
- **Mercury (Hg²⁺)**: Atomic number = 80, loses 2 electrons, so it has 78 electrons.
- **Lead (Pb⁴⁺)**: Atomic number = 82, loses 4 electrons, so it has 78 electrons.
- **Conclusion for Set 3**: Both Hg²⁺ and Pb⁴⁺ have 78 electrons, so they are isoelectronic.

5. **Analyzing the Fourth Set**:
- **Hydrogen (H)**: Atomic number = 1, electrons = 1.
- **Helium (He)**: Atomic number = 2, loses 1 electron (He⁺), so it has 1 electron.
- **Lithium (Li)**: Atomic number = 3, loses 2 electrons (Li²⁺), so it has 1 electron.
- **Beryllium (Be)**: Atomic number = 4, loses 3 electrons (Be³⁺), so it has 1 electron.
- **Conclusion for Set 4**: All species have 1 electron, so they are isoelectronic.

### Final Conclusion:
- **Sets that consist of only isoelectronic species**: Set 1, Set 3, and Set 4.