These two combinations are isotopes of helium, and bothare stable. On earth helium-4 (two protons & two neutrons) is about a million times more abundant then helium-3 (two protons & one neutron). A link can be found below for more information.
In a simple sense, protons and neutrons keep each other balanced. If there's an uneven number of either, this balance is destroyed.
Hydrogen-1 (protium):1 proton, 0 neutrons (stable) Helium-2 (diproton): 2 protons, 0 neutrons (unstable - short half-life) Helium-3: 2 protons, 1 neutron (stable) Lithium-4: 3 protons, 1 neutron (unstable - extremely short half-life) Lithium-5: 3 protons, 2 neutrons (unstable - extremely short half-life) Beryllium-5: 4 protons, 1 neutron (mostly theoretical, unstable, extremely short half-life if formed) Beryllium-5: 4 protons, 2 neutron (unstable - extremely short half-life) Beryllium-5: 4 protons, 3 neutron (unstable - extremely short half-life) Boron-6: 5 protons, 1 neutron (mostly theoretical, extremely short half-life if formed) Boron-7: 5 protons, 2 neutron (unstable - extremely short half-life) Boron-8: 5 protons, 3 neutron (unstable - short half-life) Boron-9: 5 protons, 4 neutron (unstable - extremely short half-life) Carbon-8: 6 protons, 2 neutrons (unstable - extremely short half-life) Carbon-9: 6 protons, 3 neutrons (unstable - short half-life) Carbon-10: 6 protons, 4 neutrons (unstable - short half-life) Carbon-11: 6 protons, 5 neutrons (unstable - short half-life) Nitrogen-10: 7 protons, 3 neutrons (unstable - extremely short half-life) Nitrogen-11: 7 protons, 4 neutrons (unstable - extremely short half-life) Nitrogen-12: 7 protons, 5 neutrons (unstable - short half-life) Nitrogen-13: 7 protons, 6 neutrons (unstable - short half-life) Oxygen-12: 8 protons, 4 neutrons (unstable - extremely short half-life) Oxygen-13: 8 protons, 5 neutrons (unstable - extremely short half-life) Oxygen-14: 8 protons, 6 neutrons (unstable - short half-life) Oxygen-15: 8 protons, 7 neutrons (unstable - short half-life) Fluorine-14: 9 protons, 5 neutrons (unstable - extremely short half-life) Fluorine-15: 9 protons, 6 neutrons (unstable - extremely short half-life) Fluorine-16: 9 protons, 7 neutrons (unstable - extremely short half-life) Fluorine-17: 9 protons, 8 neutrons (unstable - short half-life) Neon-16: 10 protons, 6 neutrons (unstable - extremely short half-life) Neon-17: 10 protons, 7 neutrons (unstable - extremely short half-life) Neon-18: 10 protons, 8 neutrons (unstable - short half-life) Neon-19: 10 protons, 9 neutrons (unstable - short half-life) ... and the list goes on
The natural isotope 4He has 2 protons and 2 neutrons. The natural isotope 3He has 2 protons and 1 neutron.
Protons: 2 neutrons: 2 electrons: 2 Helium-3: 2 protons, 1 neutron, 2 electrons Helium-4: 2 protons, 2 neutrons, 2 electrons
It is true that unstable nuclei will undergo radioactive decay in order to gain stability. These include nuclei of #43 Technitium (Tc), any nucleus containing more that 83 protons and any nucleus with a high neutron-to-proton ratio, such as carbon-14. The most common forms of decay are by emission of an alpha particle (2 protons and 2 neutrons ... a helium nucleus!) or a beta-negative decay in which a neutron bcomes a proton by emitting an electron and an antineutrino.
A proton can be divided into 2 Ups and a Down quark, and a neutron into 2 Downs and an Up quark. In general the quark is the elementary particle from which protons and neutron are formed.
Hydrogen-1 (protium):1 proton, 0 neutrons (stable) Helium-2 (diproton): 2 protons, 0 neutrons (unstable - short half-life) Helium-3: 2 protons, 1 neutron (stable) Lithium-4: 3 protons, 1 neutron (unstable - extremely short half-life) Lithium-5: 3 protons, 2 neutrons (unstable - extremely short half-life) Beryllium-5: 4 protons, 1 neutron (mostly theoretical, unstable, extremely short half-life if formed) Beryllium-5: 4 protons, 2 neutron (unstable - extremely short half-life) Beryllium-5: 4 protons, 3 neutron (unstable - extremely short half-life) Boron-6: 5 protons, 1 neutron (mostly theoretical, extremely short half-life if formed) Boron-7: 5 protons, 2 neutron (unstable - extremely short half-life) Boron-8: 5 protons, 3 neutron (unstable - short half-life) Boron-9: 5 protons, 4 neutron (unstable - extremely short half-life) Carbon-8: 6 protons, 2 neutrons (unstable - extremely short half-life) Carbon-9: 6 protons, 3 neutrons (unstable - short half-life) Carbon-10: 6 protons, 4 neutrons (unstable - short half-life) Carbon-11: 6 protons, 5 neutrons (unstable - short half-life) Nitrogen-10: 7 protons, 3 neutrons (unstable - extremely short half-life) Nitrogen-11: 7 protons, 4 neutrons (unstable - extremely short half-life) Nitrogen-12: 7 protons, 5 neutrons (unstable - short half-life) Nitrogen-13: 7 protons, 6 neutrons (unstable - short half-life) Oxygen-12: 8 protons, 4 neutrons (unstable - extremely short half-life) Oxygen-13: 8 protons, 5 neutrons (unstable - extremely short half-life) Oxygen-14: 8 protons, 6 neutrons (unstable - short half-life) Oxygen-15: 8 protons, 7 neutrons (unstable - short half-life) Fluorine-14: 9 protons, 5 neutrons (unstable - extremely short half-life) Fluorine-15: 9 protons, 6 neutrons (unstable - extremely short half-life) Fluorine-16: 9 protons, 7 neutrons (unstable - extremely short half-life) Fluorine-17: 9 protons, 8 neutrons (unstable - short half-life) Neon-16: 10 protons, 6 neutrons (unstable - extremely short half-life) Neon-17: 10 protons, 7 neutrons (unstable - extremely short half-life) Neon-18: 10 protons, 8 neutrons (unstable - short half-life) Neon-19: 10 protons, 9 neutrons (unstable - short half-life) ... and the list goes on
2 protons, 2 electrons, and 1 neutron
The natural isotope 4He has 2 protons and 2 neutrons. The natural isotope 3He has 2 protons and 1 neutron.
Helium-4 has 2 protons and 2 neutrons. The less common helium-3 has 2 protons but only 1 neutron. There are also several additional isotopes (that is, different number of neutrons), but those are unstable (radioactive).
1 neutron It has in its nucleus 1 neutron and 2 protons so its mass number is 3, hence whay it is called helium-3. (Mass number = # of protons + # of neutrons)
Atomic nuclei with more than 84 protons or a large neutron-to-proton ratio is unstable. These nuclei will lose alpha-particles (generally reduces the nucleus by 2 protons and 2 neutrons) or beta-particles (generally turns a neutron to a proton) until it becomes stable. This can take billions of years or a fraction of a second, depending on the isotope.
2 protons and 2 neutron
2
A proton can be divided into 2 Ups and a Down quark, and a neutron into 2 Downs and an Up quark. In general the quark is the elementary particle from which protons and neutron are formed.
2 protons, 2 neutrons
The isotope helium-3 has only one neutron. It has 1 neutron, 2 protons and 2 electrons. You can get an atom's number of neutrons by subtracting its atomic number from its mass (nucleon) number.
Protons: 2 neutrons: 2 electrons: 2 Helium-3: 2 protons, 1 neutron, 2 electrons Helium-4: 2 protons, 2 neutrons, 2 electrons