What occurs when 2 or more organisms or populations in a community rely or need similar limiting resources.

Competition occurs when 2 or more organisms or populations in a community rely or need similar limiting resources.

Explanation:

When many organisms living in the same community rely on similar limiting resources competition occurs. Every organism has its own living space and specialty which includes basic needs such as nourishment, shelter, temperature, and moisture. When the amount of organisms increases, they compete to have a better survival for the sharing of similar resources. When different species population occupy a similar niche, they compete themselves for these limited natural resources. Two or more species may have similar basic needs that occupy the same niche.

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.