Which group of periodic table have large negative energy of activation ?

Options

A. Alkali metal
B. Zero group
C. Halogen family
D. Alkaline earth metal

Answer

To determine which group of the periodic table has a large negative energy of activation, we need to analyze the electron gain enthalpy of different groups. Here’s a step-by-step solution:

### Step 1: Understand the concept of electron gain enthalpy
- Electron gain enthalpy refers to the energy change when an electron is added to a gaseous atom. A large negative value indicates that energy is released when an atom gains an electron, which is favorable.

**Hint:** Remember that a more negative electron gain enthalpy means a greater tendency to gain electrons.

### Step 2: Analyze the Alkali Metals (Group 1)
- Alkali metals (Li, Na, K, etc.) have the electronic configuration of ns1. They tend to lose one electron to achieve a noble gas configuration.
- Since they lose electrons rather than gain them, their electron gain enthalpy is not large and negative.

**Hint:** Alkali metals prefer to lose electrons to achieve stability, not gain them.

### Step 3: Analyze the Noble Gases (Group 18)
- Noble gases (He, Ne, Ar, etc.) have a complete octet and are very stable. They do not tend to gain electrons because they already have a full valence shell.
- Therefore, their electron gain enthalpy is not large and negative; in fact, it is often positive or negligible.

**Hint:** Noble gases are stable and do not readily accept electrons.

### Step 4: Analyze the Halogens (Group 17)
- Halogens (F, Cl, Br, I) have the electronic configuration of ns2 and p5. They are one electron short of achieving a noble gas configuration.
- When halogens gain an electron, they release a significant amount of energy, resulting in a large negative electron gain enthalpy.

**Hint:** Halogens are very reactive because they readily gain an electron to achieve stability.

### Step 5: Analyze the Alkaline Earth Metals (Group 2)
- Alkaline earth metals (Be, Mg, Ca, etc.) have the electronic configuration of ns2. They tend to lose two electrons to achieve a noble gas configuration.
- Similar to alkali metals, they do not have a large negative electron gain enthalpy since they prefer to lose electrons.

**Hint:** Alkaline earth metals also prefer to lose electrons rather than gain them.

### Conclusion
- The group with a large negative energy of activation (or electron gain enthalpy) is the **Halogens (Group 17)**. They have a strong tendency to gain an electron, resulting in a significant release of energy.

**Final Answer:** Halogens (Group 17) have large negative energy of activation.