What is the method for calculating atomic mass from isotopes?

[neon1234]

hi i was wondering if anybody could help me? for calculating if there's a missing part how do i solve it ? i have a picture ... how would i figure out the third part ..?

 

[neon1234]

answer quick please

 

[wajagawa]

Hi Friend,

When you are looking for help on these boards please be patient and wait for someone to assist you.

As for your question on how to calculate the atomic mass, in order to find the atomic mass of an element you must take the weighted average of its isotopes (based on percent abundance). You can take a look at how to do a weighted average from wikipedia or google it.