The atomic volume of the transition elements are low compared with elements in neighboring group `1` and `2` because:

Options

A. The number charge is poorly screened and so attract all the electrons more strongly
B. the extra electrons added inner orbitals
C. (A) and (B) both
D. none

Answer

To answer the question regarding why the atomic volume of transition elements is low compared to elements in neighboring groups 1 and 2, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Atomic Volume**:
- Atomic volume is defined as the volume occupied by one mole of an element. It is influenced by the size of the atoms and the arrangement of electrons around the nucleus.

2. **Comparing Groups**:
- Transition elements belong to the d-block of the periodic table, while groups 1 and 2 consist of s-block elements. The atomic volume of transition elements is generally lower than that of s-block elements.

3. **Nuclear Charge and Shielding**:
- Transition elements have a higher nuclear charge due to the increasing number of protons as you move across the period. However, the d-electrons provide poor shielding for the valence electrons.
- Poor shielding means that the effective nuclear charge (Z_eff) experienced by the valence electrons is higher, leading to a stronger attraction between the nucleus and the valence electrons.

4. **Effect of Poor Shielding**:
- Because the d-electrons do not effectively shield the nucleus's positive charge, the valence electrons are pulled closer to the nucleus. This results in a smaller atomic radius and, consequently, a smaller atomic volume.

5. **Conclusion**:
- The combination of high nuclear charge and poor shielding leads to a stronger attraction between the nucleus and the electrons in transition elements, resulting in lower atomic volumes compared to the s-block elements.

### Final Answer:
The atomic volume of transition elements is low compared to elements in neighboring groups 1 and 2 because the nuclear charge is poorly screened, which causes all the electrons to be attracted more strongly.