Why is hydrogen unique among the elements

Design techniques and materials that reduce the negative environmental impact of a structure are referred to as

An electron moved from shell n = 2 to shell n = 1. what most likely happened during the transition? a fraction of a photon was added. a photon of energy was absorbed. a fraction of a photon was removed. a photon of energy was released.

Earth's axis of rotation is tilted at an angle of 23.5 degrees. what is one change you would see on earth if its axis was not tilted?