Question

The first ionization enthalpy of carbon atom is greater than that of boron where as the reverse is true for second ionization enthalpy.Explain

Answer 1

First,we should take a look at the electronic configurations of both the atoms.

C - 1s^2 , 2s^2, 2p^2
B - 1s^2, 2s^2,2p^1

The answer to the first question is very simple.The size of a carbon atom is smaller than boron.So the Valence electron of carbon faces a greater nuclear force( nuclear charge) than that of boron.In order to break that,carbon needs greater energy ,hence the first I.E of carbon is higher.

Coming to the second question, let's take a look at the electronic configurations of the atoms again but now without an electron.

C - 1s^2, 2s^2,2p^1
B - 1s^2 , 2s^2

Boron has a fully filled orbital (2s2) than carbon(2p1). And since, fully filled orbitals have more stability than partially filled orbitals so greater amount of energy will be needed to remove an electron from boron.So in this case, the second I.E of boron is higher than that of carbon.

Hope This Helps.

Answer 2

Answer:

Explanation:

ELECTRONIC CONFIGURATION:

Carbon: 1s2, 2s2, 2p2

Boron: 1s2, 2s2, 2p1

there are unpaired electrons in 2p orbitals of both carbon and boron. But in carbon since positive charge is slightly greater thus it's first ionization energy is greater than that of boron.

Now for second ionization enthalpy when first electron has already been removed from both carbon and boron.Carbon has it's p electron at almost same distance form the nucleus as it earlier had the outermost electron in first ionization,But in case of boron the second electron is to to be removed from sub level s orbital which more closer to the nucleus. Thus Second ionization enthalpy of boron is slightly greater than that of carbon.