Which of the following compounds has two lone pairs on the central atom?

Which molecular orbitals are formed, when the 1s orbitals of two hydrogen atoms combine to form a hydrogen molecule?

Consider the following structures I-IV. Which two species represent constitutional isomers? 

For the following reaction, identify the Lewis base. 

Which of the following structures contains an alkene? 

Which element has the ground state electron configuration of 1s22s22p63s23p4?

Bonus question Rank the following in order of decreasing importance as a contributing resonance structure to the molecular structure of acetone, CH3COCH3 (more important > less important)

Identify the following compound expected to be the most soluble in butane, CH3CH2CH2CH3?

Rank the indicated protons in order of increasing acidity.

What is the electronic configuration for the nitride ion?