The electron in the He+ ion is excited to the n = 2 principal state. What is the energy of the electron now?

= -13.6 eV

Explanation:

E = -13.6 ÷

where n is the principal state

Z is atomic number

and E is energy in electron volts.

Given that n = 2 and Helium Z = 2

⇒ E = -13.6 ÷

= -13.6 eV

I believe this is helpful and easy to follow.

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.

elements make up everything, and they combine to make compounds.

the answer is c