What is the mass number of a Cesium (Cs) atom that has 78 neutrons?
a. 55
b. 132.9***
c. 133
d. 132
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 = ?
the answer is 133
To find the mass number of a Cesium (Cs) atom that has 78 neutrons, we need to identify the atomic symbol and understand the relationship between the atomic number, the number of protons, and the mass number.
First, we need to know the atomic number of Cesium, which is 55. The atomic number represents the number of protons in an atom.
The mass number of an atom is the sum of its protons and neutrons. To find the mass number, add the number of protons (which is equal to the atomic number) and the number of neutrons.
In this case, the number of neutrons is given as 78. To find the mass number, add 55 (atomic number) + 78 (number of neutrons), which equals 133.
Therefore, the correct answer is c. 133, as it represents the mass number of a Cesium (Cs) atom with 78 neutrons.