Which of the following statement concerning ionisation energy is not correct ?

Options

A. The `IE_(2)` is always more than the first.
B. Within a group, there is a gradual increase in ionisation energy because nuclear charge increases.
C. Ionisation energies of `Be` is more than `B`.
D. Ionisation energies of noble gases are high.

Answer

To determine which statement concerning ionization energy is not correct, we will analyze each statement one by one.

### Step 1: Analyze Statement 1
**Statement 1:** The ionization energy (IE2) is always more than that of the first ionization energy (IE1).

- **Explanation:** This statement is true. The first ionization energy refers to the energy required to remove the first electron from a neutral atom, while the second ionization energy refers to the energy required to remove an electron from a positively charged ion (cation). Since removing an electron from a cation is more difficult due to increased positive charge and reduced electron-electron repulsion, IE2 is indeed greater than IE1.

### Step 2: Analyze Statement 2
**Statement 2:** Within a group, there is a gradual increase in ionization energy because nuclear charge increases.

- **Explanation:** This statement is incorrect. As we move down a group in the periodic table, the atomic size increases due to the addition of electron shells. Although the nuclear charge does increase, the effect of increased distance between the nucleus and the outermost electrons (along with increased electron shielding) outweighs this, leading to a decrease in ionization energy. Therefore, this statement is not correct.

### Step 3: Analyze Statement 3
**Statement 3:** The ionization energy of B (Boron) is more than that of B (Beryllium).

- **Explanation:** This statement is true. Beryllium (Be) has a filled 2s subshell, while Boron (B) has one electron in the 2p subshell. The 2s subshell has a greater penetration effect and is more stable than the 2p subshell, making it easier to remove an electron from Boron than from Beryllium. Thus, the ionization energy of Boron is indeed higher than that of Beryllium.

### Step 4: Analyze Statement 4
**Statement 4:** The ionization energy of noble gases is high.

- **Explanation:** This statement is true. Noble gases have a complete valence shell, making them very stable. As a result, a significant amount of energy is required to remove an electron from them, leading to high ionization energies.

### Conclusion
After analyzing all the statements, we conclude that the incorrect statement is **Statement 2**.

### Final Answer
The statement concerning ionization energy that is not correct is **Statement 2**.

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