How many electrons, protons, and neutrons are contained in the 17o?

The Atomic Number and Atomic Mass of ¹⁷O are 8 and 17 respectively.

Atomic Number:
                         Atomic Number of Element is the Number of Protons contained by the Element. So, there are 8 Protons in ¹⁷O.

Atomic Mass:
                     Atomic Mass of Element is the total number of Protons and Neutrons present in the Nucleus of that element.
So,
                    Atomic Mass  =  # of Protons + # of Neutrons

As the Atomic mass of ¹⁷O is 17 and it has 8 protons, So # of Neutrons are calculated as,

                     # of Neutrons  =  Atomic Mass - # of Protons

                     # of Neutrons  =  17 - 8

                     # of Neutrons  =  9
And,
As there is no charge on ¹⁷O, so the number of Electrons and Protons are equal. i.e.
                     # of Electrons  =  8

Result:
             In ¹⁷O Number of Neutrons are 9, Number of Protons are 8 and Number of Electrons are 8.