What is the mass number of a Cesium (Cs) atom that has 78 neutrons?
a. 55
b. 132.9***
c. 133
d. 132
3 answers
should i round up to 133 or keep it at 132.9?
It isn't 132.9. Mass numbers are ALWAYS WHOLE number.
mass # = # protons + # neutrons.
# protons Cs = 55. That's the atomic number from the periodic table.
# neutrons from the problem is 78.
78 + 55 = ?
mass # = # protons + # neutrons.
# protons Cs = 55. That's the atomic number from the periodic table.
# neutrons from the problem is 78.
78 + 55 = ?
the answer is 133
1 answer