Analysis of a 10.15 g sample of a compound known to contain only phosphorus and oxygen indicates a phosphorus content of 4.433 g. what is the empirical formula of this compound

find mass of oxygen by subtracting mass of phosphorus from the total mass

divide the masses by the molar mass to get moles

divide moles by the smallest amount of moles

multiply by 2 to get a nice number

P4O5

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."

i just learnt this recently but i need to look through my notes again