18 protons and 18 neutrons
The number of protons
atomic mass number - protons = number or neutrons
The mass number of an element is equal to the sum of the elements neutrons and protons.
mass no. = no. of protons + no. of neutrons
Number of protons + Number of neutrons = Mass number(number of nucleons)
Mass number is about the neutrons and protons. The total of neutrons and protons.
The "25" is the mass number, which is the sum of the number of neutrons and protons. We don't know how many neutrons there are, but we do know how many protons magnesium has. The atomic number of an element is the same as the number of protons, so locating a Periodic Table, magnesium is number 12, which means 12 protons. If mass number = number of protons + number of neutrons, then number of neutrons = mass number - number of protons (or atomic number). So 25 - 12 = 13 neutrons in 25Mg.
Mass number!:)
The number of protons
79; the mass number is the sum of the protons and neutrons, and the atomic number is the number of protons. So if you take the mass number (protons + neutrons) minus the atomic number (protons), you get the number of neutrons.
atomic mass number - protons = number or neutrons
A carbon atom with a mass number of 12 has 6 protons (which is the atomic number of carbon) and 6 neutrons.
The mass number of an element is equal to the sum of the elements neutrons and protons.
Uranium isotopes have 92 protons and electrons; the number of neutrons is different for each isotope.Number of neutrons = Mass number - Number of protons
Americium has 95 protons and electrons. Number of neutrons: Atomic Mass of an isotope - number of protons
84 protons, the same as the atomic number, and (210 - 84) or 126 neutrons. The numbers of protons and neutrons together equals the mass number.
The combined number of protons and neutrons is known as the mass number of an atom. It can be used to calculate the atomic mass by adding the total number of protons and neutrons in the nucleus of an atom.