The first ionisation enthalpy of the elements C,N,P,Si are in the order of

Options

A. `CltNltSiltp`
B. `NltSiltCltP`
C. `SiltPltCltN`
D. `PltSiltNltC`

Answer

To determine the order of first ionization enthalpy of the elements carbon (C), nitrogen (N), phosphorus (P), and silicon (Si), we can follow these steps:

### Step 1: Understand Ionization Enthalpy
Ionization enthalpy is the amount of energy required to remove an electron from an isolated gaseous atom. Generally, it increases across a period and decreases down a group in the periodic table.

### Step 2: Identify the Position of Elements in the Periodic Table
- Carbon (C) and Silicon (Si) are in Group 14.
- Nitrogen (N) and Phosphorus (P) are in Group 15.

### Step 3: Analyze Trends Across a Period
As we move from left to right across a period, the ionization enthalpy increases due to the increase in effective nuclear charge, which means that the outer electrons are held more tightly by the nucleus.

### Step 4: Analyze Trends Down a Group
As we move down a group, the ionization enthalpy decreases because the outer electrons are farther away from the nucleus and are shielded by inner electron shells, making them easier to remove.

### Step 5: Compare Ionization Enthalpies of the Given Elements
- Between C and Si: Carbon (C) has a higher ionization enthalpy than Silicon (Si) because C is higher up in the group.
- Between N and P: Nitrogen (N) has a higher ionization enthalpy than Phosphorus (P) for the same reason.
- Comparing C and N: Nitrogen (N) has a higher ionization enthalpy than Carbon (C) because it is in a higher group (Group 15 vs Group 14).
- Comparing P and Si: Silicon (Si) has a higher ionization enthalpy than Phosphorus (P).

### Step 6: Final Order of Ionization Enthalpy
Based on the above analysis, we can arrange the elements in the order of their first ionization enthalpy from highest to lowest:
1. Nitrogen (N)
2. Carbon (C)
3. Silicon (Si)
4. Phosphorus (P)

Thus, the order of first ionization enthalpy for C, N, P, Si is:
**N > C > Si > P**

### Final Answer
The order of first ionization enthalpy of the elements C, N, P, Si is: **N > C > Si > P**

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