What does 3.4225e-8 mean

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?

How many moles of bromine are needed to produce 3.23 moles of potassium bromide

How many lone pairs of electrons are on the central atom of no3- and what is the molecular shape? one, trigonal planar zero, trigonal pyramidal zero, trigonal planar one, tetrahedral one, trigonal pyramidal