What is the definition of half life

What are the first three quantum numbers for the electrons located in subshell 2s?

Need what is special about water as a compound? how does water regulate climate? what drives water evaporation?   why is the water vapor fresh water when it rises from the ocean? why might freshwater in the form of snow take longer to enter the water cycle again than liquid precipitation?   what is an aquifer? what role do people play in the water cycle? plz just answer as many as you can ! thx if you !

Does the number of ions in solution increase, decrease, or remain constant? it continuously decreases. it continuously increases. it decreases at first, then increases. it increases at first, then decreases.