The mass number of an atom that has 53 protons, 78 neutrons, and 54 electrons would be 131.
A mass number can be described as the sum total of the number of protons and neutrons that are contained within the nucleus of an atom.
If we want to calculate the mass number of an atom, we need to add the number of neutrons present inside the atoms with the number of protons present inside the atom.
As mentioned in the question, the number of protons inside the said atom is 53 whereas the number of neutrons is 78. Hence,
53+78= 131
To learn more about mass number, click here:
brainly.com/question/28409714
#SPJ4
