11.  If an atom has an atomic number of 15 and an atomic weight of 31, the atom will have a total of  how many          electrons?  How many neutrons will this atom have?
        a.  15;16         b.  15;31         c.  16;31         d.  31;46

atomic number = number of protons = number of electrons
atomic number of 15 = 15 protons = 15 electrons

atomic weight = number of protons + number of neutrons
31 = 15 + X neutrons
31 -15 = 16 neutrons

If you had difficulty with this problem, be sure that you have memorized the material in the table given in response to question #5 of this quiz. 

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Emma Erdahl, Associate Professor of Biology
Northern Virginia Community College
Revised 8/23/00