Among the species given below, the total number of diamagnetic species is _________. H atom, `NO_(2)` monomer,`O_(2)^(-)` (superoxide), dimeric sulphur in vapour phase,
`Mn_(3)O_(4),(NH_(4))_(2)["FeCl"_(4)], (NH_(4))_(2)["NiCl"_(4)],K_(2)MnO_(4), K_(2)CrO_(4)`

Answer

To determine the total number of diamagnetic species among the given options, we will analyze each species one by one, focusing on their electronic configurations and the presence of unpaired electrons.

### Step-by-Step Solution:

1. **H atom**:
- The hydrogen atom has one electron (1s¹).
- Since it has one unpaired electron, it is **paramagnetic**.

2. **NO₂ (monomer)**:
- The nitrogen dioxide molecule has an odd number of electrons (11 total).
- It has unpaired electrons, making it **paramagnetic**.

3. **O₂⁻ (superoxide)**:
- The superoxide ion has 17 electrons (16 from O₂ and 1 extra).
- It has unpaired electrons, so it is **paramagnetic**.

4. **Dimeric sulfur in vapor phase**:
- Dimeric sulfur (S₂) has 16 electrons.
- The electronic configuration shows that it has unpaired electrons, thus it is **paramagnetic**.

5. **Mn₃O₄**:
- The oxidation states of manganese in Mn₃O₄ are +2 and +3.
- In both oxidation states, there are unpaired electrons, making it **paramagnetic**.

6. **(NH₄)₂[FeCl₄]**:
- The oxidation state of iron in this complex is +2.
- The electronic configuration of Fe²⁺ (3d⁶) shows unpaired electrons, so it is **paramagnetic**.

7. **(NH₄)₂[NiCl₄]**:
- The oxidation state of nickel in this complex is +2.
- The electronic configuration of Ni²⁺ (3d⁸) shows unpaired electrons, making it **paramagnetic**.

8. **K₂MnO₄**:
- The oxidation state of manganese in K₂MnO₄ is +6.
- The electronic configuration of Mn⁶⁺ (3d¹) shows one unpaired electron, so it is **paramagnetic**.

9. **K₂CrO₄**:
- The oxidation state of chromium in K₂CrO₄ is +6.
- The electronic configuration of Cr⁶⁺ (3d⁰) shows no unpaired electrons, making it **diamagnetic**.

### Summary of Results:
- **Diamagnetic Species**: K₂CrO₄ (1 species)
- **Paramagnetic Species**: H atom, NO₂, O₂⁻, dimeric sulfur, Mn₃O₄, (NH₄)₂[FeCl₄], (NH₄)₂[NiCl₄], K₂MnO₄ (8 species)

### Total Number of Diamagnetic Species:
The total number of diamagnetic species is **1**.

---