What is the order of successive ionisation enthalpies?

Options

A. `IE_(III)gtIE_(II)gtIE_(1)`
B. `IE_(1)gtIE_(II)gtIE_(III)`
C. `IE_(II)gtIE_(I)gtIE_(III)`
D. `IE_(III)gtIE_(I)gtIE_(II)`

Answer

To determine the order of successive ionization enthalpies, we need to understand the concept of ionization enthalpy and how it changes with the removal of electrons from an atom.

### Step-by-Step Solution:

1. **Definition of Ionization Enthalpy**:
- Ionization enthalpy is the minimum energy required to remove an electron from an atom in its gaseous state.

2. **Understanding Successive Ionization**:
- When the first electron is removed from an atom, the remaining electrons experience an increase in effective nuclear charge (the net positive charge experienced by the electrons). This is because there are fewer electrons to shield the remaining electrons from the nucleus.

3. **Effect of Removing Electrons**:
- After the removal of the first electron, the effective nuclear charge on the remaining electrons increases. This makes it more difficult to remove subsequent electrons because the remaining electrons are held more tightly by the nucleus.

4. **Trends in Ionization Enthalpy**:
- The first ionization enthalpy (I1) is the energy required to remove the first electron.
- The second ionization enthalpy (I2) is the energy required to remove the second electron after the first has been removed.
- The third ionization enthalpy (I3) is the energy required to remove the third electron after the first two have been removed.

5. **Order of Ionization Enthalpies**:
- As more electrons are removed, the effective nuclear charge on the remaining electrons increases, making it progressively harder to remove additional electrons. Therefore, the order of successive ionization enthalpies is:
\[ I_3 > I_2 > I_1 \]
- This means that the third ionization enthalpy is greater than the second, which in turn is greater than the first.

### Final Answer:
The order of successive ionization enthalpies is:
\[ I_3 > I_2 > I_1 \]