What are the differences among an mechanical mixture, a suspension and a colloid?

Organisms are more likely to be more preserved in mud than sand because mud is moist and wet, while sand is very dry.

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.

Ithink iit might be