As, Sb and Bi show little or no tendency to form negative ions of the type `M^(3-)`. This is because

Options

A. these elements are less electronegative
B. their atoms have larger size
C. they are unable to hold the added elements due to insert pair effect
D. they do not process half filled np subshells

Answer

To answer the question regarding why arsenic (As), antimony (Sb), and bismuth (Bi) show little or no tendency to form negative ions of the type M^(3-), we can analyze the properties of these elements step by step.

### Step-by-Step Solution:

1. **Understanding the Group**:
- Arsenic (As), Antimony (Sb), and Bismuth (Bi) are elements in Group 15 of the periodic table. The group also includes nitrogen (N) and phosphorus (P).

2. **Electronegativity**:
- Electronegativity is the tendency of an atom to attract electrons. As we move down the group from nitrogen to bismuth, the electronegativity decreases.
- Since As, Sb, and Bi are less electronegative compared to nitrogen and phosphorus, they are less likely to attract additional electrons to form negative ions (M^(3-)).

3. **Atomic Size**:
- The atomic size increases as we move down the group due to the addition of electron shells.
- Larger atomic size means that the outer electrons are further from the nucleus, which reduces the effective nuclear charge experienced by these electrons. This makes it harder for these atoms to hold onto additional electrons.

4. **Inert Pair Effect**:
- The inert pair effect refers to the tendency of the s-electrons (in this case, the ns² electrons) to remain non-bonding in heavier p-block elements.
- While this effect stabilizes lower oxidation states, it does not directly influence the formation of negative ions. Therefore, it is not a reason for the lack of M^(3-) ions.

5. **Half-filled Subshell**:
- The configuration of these elements shows that they have a half-filled p subshell (ns² np³). However, this does not prevent them from forming negative ions, as the half-filled configuration is more relevant to stability in bonding rather than the ability to gain electrons.

6. **Conclusion**:
- The primary reasons As, Sb, and Bi do not form M^(3-) ions are their lower electronegativity and larger atomic size. Therefore, the correct options are:
- Option A: These elements are less electronegative.
- Option B: Their atoms have larger size.