pH is a symbolic representation of:

and for water we now that:

that means the text give us the information to calculate the concentration of protons and therefore the concentration of ions OH-:

therefore the concentration of OH- can be calculated:

but they are not asking about the concetration of OH- they ask about concentration of Ba(OH)2 and for that we need to know the disolution stechiometry

Whic mean the concentration of Ba(OH)2 is half the concentration of OH-:
1.molecular element
2.ionic compound
3.molecular compound
4. molecular compound
- We cannot change protons of any element
- So the atomic number is 33
- The element is Arsenic(As)
Now here is 36 electrons so it's. tri cation.
Symbol

Answer: 16 neutrons
Explanation: The atomic number for any element is the number of protons in its atomic nuclei. In a neutral atom, the number of electrons are the same as the number of protons. The atomic mass (mass number) is the sum of the protons and neutrons in the nucleus. Mass number can vary due to the fact that the number of neutrons can vary. Isotopes are named for their mass numbers.
So, this element has 15 protons (atomic number), 15 electrons, and 16 neutrons (mass number minus atomic number).
This isotope is phosphorus-31, which has atomic number 15.