Which molecule/molecular compound is joined by a single covalent bond? O2 or N2 or Br2 or CO2?

If the particles in a sample of matter have an orderly arrangement and move only in place, the sample is a

This drawing shows a human body system. what is the primary function of this body system?

What are the first two quantum numbers for the electrons located in subshell 4d? what are the first three quantum numbers for the electrons located in subshell 2s? how many electrons can be held in a sublevel l = 3? how many electrons can be held in the energy level n = 4? how many electrons in an atom can share the quantum numbers n = 4 and l = 3?