Anamolous behaviour of fluorine in group 17 is due to

Options

A. (a) Small size
B. (b) High electronegativity
C. (c) Low F-F bond dissociation enthalpy and absence of vacant d orbital
D. (d) All of these

Answer

To understand the anomalous behavior of fluorine in Group 17 (the halogens), we need to analyze the reasons behind this behavior step by step.

### Step 1: Identify the Group and Element
Fluorine is the first element in Group 17 of the periodic table, which includes other halogens like chlorine, bromine, iodine, and astatine.

**Hint:** Remember that Group 17 elements are known as halogens, and they typically exhibit similar chemical properties.

### Step 2: Understand Oxidation States
Fluorine predominantly exhibits a -1 oxidation state because it needs one more electron to complete its outer shell (2p). In contrast, other halogens can show a range of oxidation states (e.g., -1, +1, +3, +5, +7).

**Hint:** Consider how the electronic configuration influences the ability of an element to gain or lose electrons.

### Step 3: Analyze the Small Size of Fluorine
Fluorine has a very small atomic size compared to other halogens. This small size leads to a strong attraction between the nucleus and the outermost electrons, making it difficult for fluorine to lose electrons and exhibit positive oxidation states.

**Hint:** Think about how atomic size affects the attraction between electrons and the nucleus.

### Step 4: Consider High Electronegativity
Fluorine is the most electronegative element, meaning it has a strong tendency to attract electrons. This high electronegativity contributes to its ability to gain an electron (resulting in a -1 oxidation state) rather than losing electrons.

**Hint:** Recall the trend of electronegativity in the periodic table as you move down a group.

### Step 5: Evaluate Bond Dissociation Enthalpy
Fluorine has a low bond dissociation enthalpy for the F-F bond due to the small size of the fluorine atoms, which leads to significant repulsion between non-bonding electrons. This instability means that less energy is required to break the bond.

**Hint:** Consider how bond strength is influenced by atomic size and electron repulsion.

### Step 6: Absence of Vacant D Orbitals
Fluorine does not have vacant d orbitals (as it is in the second period), which restricts its ability to expand its valency. In contrast, larger halogens like chlorine have vacant d orbitals that allow them to exhibit multiple oxidation states.

**Hint:** Understand the role of d orbitals in determining the oxidation states of elements.

### Conclusion
All of the above factors contribute to the anomalous behavior of fluorine in Group 17. Therefore, the correct answer to the question is option D: all of these reasons (small size, high electronegativity, low F-F bond dissociation enthalpy, and absence of vacant d orbitals) explain why fluorine behaves differently from other halogens.

**Final Answer:** Option D: All of these.