The atom is neutral as it has two positive protons and two negative electrons. A helium atom that has lost or gained an electron is an ion. The ion has two positive protons but one electron so it ...

Helium is notoriously hard to contain because, like hydrogen, it is a tiny little atom even by atomic standards. It also expands about 750 times when it turns into a gas, according to the post’s ...

For example, a helium atom has an atomic mass of 4, but an atomic number (or positive charge) of 2. Since electrons have almost no mass, it seemed that something besides the protons in the nucleus ...

“At low temperatures, models of reactivity must include the effects of the permanent electric dipoles and quadrupole moments ...

In this configuration every atom has on the average four nearest neighbours ... For T T0 the specific heat is given by (4) Though actually the X-point of helium resembles rather a phase transition ...

For example, a helium atom has an atomic mass of 4, but an atomic number (or positive charge) of 2. Since electrons have almost no mass, it seemed that something besides the protons in the nucleus ...

While protons and neutrons are well-known and stable constituents of an atom, hyperons are unstable and are made up of either one or more quarks. Spotted in cosmic rays more than seven decades ago ...