Asubstance is composed of one kind of atom and can’t be separated into simpler substances or converted into another substance by chemical pressure. under which category would you classify this substance

How are elements arranged in a periodic table

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?

At what temperature will a solid melt ?