What are some things in life that involve chemistry and how does chemistry apply?

A lot of things in life involve chemistry. Let's start from the most obvious one - cooking.
While you are cooking, you need to mix ingredients and create homogeneous and heterogeneous mixtures, which is where chemistry is applied. Also, all of these ingredients change their physical and chemical state, which is also what chemistry studies.

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.