How many ionisation energies can carbon have?

What is ionisation energy? How does ionisation energy vary along the period in the modern periodic table ?

How does ionisation energy vary in a group ?

Why the first ionisation energy of carbon atom is greater than that of boron atom whereas, the reverse is true for the second ionisation energy.

Why the first ionisation energy of carbon atom is greater than that of boron atom whereas, the reverse is true for the second ionisation energy.

The first ionisation energy of carbon is much higher than that of silicon . Explain.

How many carbon atoms can fullerenes have?

In how many ways the internal energy can be changed ?