I need help asap solving this math problems before monday

Asingle atom of an element has 21 neutrons, 20 electrons, and 20 protons. which element is it? ok o z

Suppose you have designed a new thermometer called the x thermometer. on the x scale the boiling point of water is 129 ? x and the freezing point of water is 13 ? x. part a at what temperature are the readings on the fahrenheit and x thermometers the same?

Which of these is a physical property