Which of the following statements is not correct ?

Options

A. The first ionization energies in `("kJ mol ^(-1))` of carbon , silicon , germanium , tin and lead are 1086 , 786 , 761 ,708 and 715 respectively
B. Down the group , ionization energy decreases regularly from B to T1 in boron family
C. Among oxides of the elements of carbon family , CO is neutral , GeO is acidic and SnO is amphoteric.
D. The 4f and 5f - inner transition elements are placed separately at the bottom of the periodic table

Answer

To determine which statement is not correct, let's analyze each option step by step.

### Step 1: Analyze Option 1
**Statement**: The first ionization energies of carbon, silicon, germanium, tin, and lead are 1086, 786, 761, 708, and 715 kJ/mol respectively.

- **Analysis**: Generally, the ionization energy decreases as we move down a group in the periodic table due to an increase in atomic size and shielding effect. However, the ionization energy of lead (715 kJ/mol) is higher than that of tin (708 kJ/mol), which is an anomaly in the expected trend. Therefore, this statement is correct as it accurately reflects the observed values.

### Step 2: Analyze Option 2
**Statement**: Down the group, ionization energy decreases regularly from boron to thallium in the boron family.

- **Analysis**: While it is generally true that ionization energy decreases down a group, the trend is not smooth in the boron family (Group 13). For example, the ionization energy of gallium is higher than that of aluminum due to the poor shielding effect of the d-orbitals. Therefore, this statement is incorrect as it suggests a regular decrease.

### Step 3: Analyze Option 3
**Statement**: Among the oxides of elements of the carbon family, carbon monoxide is neutral, germanium oxide is acidic, and tin oxide is amphoteric.

- **Analysis**: This statement is correct. Carbon monoxide is typically neutral, germanium oxide (GeO2) is acidic, and tin oxide (SnO) is amphoteric, reacting with both acids and bases.

### Step 4: Analyze Option 4
**Statement**: The 4f and 5f inner transition metal elements are placed separately at the bottom of the periodic table.

- **Analysis**: This statement is correct. The lanthanides (4f) and actinides (5f) are indeed placed separately at the bottom of the periodic table due to their unique properties.

### Conclusion
After analyzing all options, we find that **Option 2 is the statement that is not correct**.

### Final Answer
**Option 2** is the correct answer as it is the statement that is not correct.

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