What does the period an element is located in tell you about that element'?

How do the energy differences between the higher energy levels of an atom compare with the energy difference between the lower energy level of the atom

Concerning the 10.0 ml of 0.50 m nacl to 100 ml of solution: when a solution is diluted, does it change the number of moles dissolved?

Aside from human impact, which of the following causes less water vapor production over a small area? (2 pderivartin