Which of these elements has the highest first ionization energy Si or C?

Answer 1

The ionization energy is the energy needed to extract an electron from an atom; first ionization energy, second, third etc. can be measured. Reactive chemical elements have lower ionization energy.
The first ionization energy for silicon is 786,5 kJ/mol.
The first ionization energy for carbon is 1 086,5 kJ/mol.

Answer 2

Carbon (C) has a higher first ionization energy than silicon (Si). This is because as you move across a period in the Periodic Table, the first ionization energy generally increases due to increasing nuclear charge pulling electrons closer. Silicon is positioned to the right of carbon in the same period, resulting in a lower first ionization energy compared to carbon.

Answer 3

Carbon. It is a smaller atom, therefore you will have to work harder to remove an electron from it.