What does hess's law Say about entalpy of a reaction

Use the table to identify the phase and phase changes of the elements under the given conditions. write the name of the substance, phase, or phase change

What is the ph of a solution that has a hydrogen ion concentration of 1.0 * 10 -9 m?

I'm learning about the periodic tables and what each subject's configuration is. for example, hydrogen is 1s^1, but i don't understand how you get that. can someone me understand how to figure out how to figure this out? sorry if the question makes no sense, but it would really a lot if you could me understand! you so much if you can!