for an atom’s electrons, how many energy sub levels are present in the principal energy level n = 4?

British cologoinst admisitrion

Idk just need points

Year  1936,  lehman predicted that the earths 'inner core' is solid. she observed that the seismic signals during her study were bent and did not pass through instead bouncing back. later it was confirmed that the earth's inner core was solid made up of nickel-iron and had a molten outer core.

+10 that is always the common denominator