What is the mass number of the atom in the diagram?
As you move up the periodic table each element has a different number of protons, neutrons and electrons. This is what gives it it’s chemical properties. The most simple Element is hydrogen, which has one proton and one electron. The next element (helium) has 2 protons and 2 electrons and therfore has the atomic number 2. Helium also has 2 neutrons. Protons and neutrons both have a mass of 1 (atomic mass unit) and the mass of an electron is neglagible. The atomic mass of helium therefore is 4 (2 protons + 2 neutrons). The atomic mass of an atom can be found by simply adding together the number of protons and neutrons. From this you should be able to work out the answer to your question. Hope this helps.
