For this chemical reaction, if you have 35 moles of o, reacting what will ah be?
czhg (8) + 502 (9) – 3002 (8) + 4h20 ah = -2 220 kj

Mgo2 is the oxidation state of manganese oxide

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.

☆ionisation energy increases across a period from na -> ar☆ionisation energy decreases down a group from li -> fr☆ionic radius decreases across a period from na -> cl☆ionic radius increases down a groupfrom f -> ii hope it clarifies your doubts