"Answer the following question in few sentences.

(a) Briefly cite the main differences between ionic, covalent, and metallic bonding
(b) What is electronegativity? Metals generally have low electronegativity values of about 1.8. How do you associate this with high conductivity of metals?
(c) Write down the typical bond strengths of C-CC - HH - H covalent bonds and a H - H secondary bond. Briefly explain the mechanism behind the secondary bonding.
(d) Based on the atomic number and valence electrons determine the possible number of covalent bonds for atoms of the elements: germanium, phosphorus, selenium, and chlorine."