Quick question. the roman number than appears after ionic compounds with transition metals, do they represent the number of atoms or its charge?

What is the mass of sodium in 3 moles of sodium chloride

Predict the products butane (c4h10) + oxygen —>

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?