Question

The mass of one electron and one proton adds up to the mass of one hydrogen atom. Charge studies showed that lithium atoms contain 3 electrons and 3 protons. The mass of one lithium atom is less than the total mass of 3 electrons and 3 protons. How can you account for this "missing" mass?

Answer 1

The missing mass in lithium atoms can be accounted for by the presence of neutrons, which are slightly heavier than protons.

Step-by-step explanation:

When considering the mass of an atom, it is customary to ignore the mass of electrons and calculate the atom's mass based on the number of protons and neutrons. The mass of an electron is much smaller compared to protons and neutrons. In the case of lithium, although it contains 3 electrons and 3 protons, the missing mass can be accounted for by the presence of neutrons, which are slightly heavier than protons. Depending on the isotope, lithium can have either 3 or 4 neutrons, contributing to the overall mass of the atom.