The atomic mass of an element whose atoms consist of eight protons, nine neutrons, and eight electrons is ?

Question

thomaster · Answer

number of protons = atomic number 
protons + neutrons = mass number

frostbite · Answer

$$m(element)=8*m(proton)+9*m(neutron)+8*m(electron)$$
Assume just to make it more easy that:
m(proton)=m(neutron)=1 u*
m(electron)= 1/1000 u
1 u=*1,66053886 · 10^-27 kg

frostbite · Answer

It is a isotope remember that.

frostbite · Answer

beside the 15.9994 is the average mass of the natural occurring isotopes multiplied with their relative percentage of appearance :)

thomaster · Answer

them it's 16.99913170 amu :P

thomaster · Answer

anyway it would be something close to 17 as 8+9 = 17 :P