Question 18 (5 points) (03.06 MC)
Which statement is true about oxygen and rocks? (5 points)
a
Both are mixtures.
Both are pure substances.
Oxygen is a mixture and a rock is a pure substance.
d
Oxygen is a pure substance and rocks are mixtures.

This would be canberra.

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.