The specific valve that prevents backflow of blood into the right ventricle when the ventricles relax is the valve.

Pulmonary valve - connects right ventricle and pulmonary trunk (which divides into right and left pulmonary arteries). It is a semilunar valve

The proton has a positive charge while the neutron has no charge they both make up the nucleus of the atom while the elections have a negative charge and surround the nucleus of the atom. the protons and electrons are used to calculate the atom's mass whereas the neutrons don't affect the mass