Which of the following molecules has three equivalent resonance structures?

What is the formula of the compound, barium peroxide?

The two equivalent resonance forms of benzene are shown below: Which of these statements is true?    

Which of the following species is isoelectronic with krypton (Kr)?

All of the following properties are associated with the Noble Gases except:

The electron configurations of five different elements are shown below. Which of these elements is expected to have the largest second ionization energy (IE2)?

The element Ar and the ions Ca2+, K+, and Cl- have the same number of electrons.  Why does the chloride ion (Cl -) have the largest radius of this isoelectronic series?

Hydrogen peroxide decomposes to water and oxygen via the following process: 2 H2O2 (l)

A red laser pointer emits light with a wavelength of 650 nm.  What is the energy gap (in eV) between the ground and excited state in the laser material?

With the exception of one of the species below, you can draw a valid Lewis Structure without violating the octet rule. Which species below must have an expanded octet?