The helium atom is a common chemical species in the universe. When considering the nucleus of the helium atom, it is identical to the alpha particle according to the number of protons and neutrons.
What is Helium Atom?
Helium atom or helium chemical element is the atom having the atomic number 2 and chemical symbol He. It is a colorless, odorless, tasteless, nontoxic, inert monoatomic gas that comes as the first in the noble gas group. The melting and boiling temperatures of helium atoms are minimal among all elements. Moreover, it is the second most abundant chemical element in the universe.
It is an s block element having the electron configuration 1s2. It has two electrons per shell. This chemical element can be found in period 1, group 18, in the periodic table of elements. At standard temperature and pressure, helium occurs as a gas.
Helium atoms were detected for the first time as an unknown, yellow spectral line signature in sunlight during a solar eclipse in 1868. This discovery was made by Georges Rayet, Captain C.T. Haig, Normal R. Pogson, and Lieutenant John Herschel.
Helium is the second simplest atom to model in quantum mechanics. It contains two electrons in atomic orbitals that surround a nucleus consisting of two protons and two neutrons. This helium atomic nucleus is identical to an alpha particle.
What is Alpha Particle?
Alpha particle contains two protons and two neutrons that are bound together into a particle. This particle is identical to the helium-4 nucleus. Generally, these particles are formed in the process of alpha decay. However, it can also form in other ways. The alpha particle was named after the first letter in the Greek alphabet. The symbol for this particle can be given as α. However, since it is identical to the nucleus of the helium atom, we can denote it as He2+ as well. This indicates a helium atom with a +2 charge.
The net spin of the alpha particle is zero. The mechanism of production of alpha particle in radioactive decay make them have a kinetic energy of around 5 MeV, and the velocity is about 4% of that of the speed of light. Therefore, alpha particles are a highly ionizing form of particle radiation that usually have a low penetration depth.
What is the Difference Between Helium Atom and Alpha Particle?
Helium atom and alpha particle are different from each other according to the presence or absence of electrons. However, the nucleus of the helium atom is identical to the alpha particle. The key difference between helium atom and alpha particle is that helium atom has two protons, two neutrons, and two electrons, whereas alpha particle only has two protons and two neutrons. Moreover, the helium atom is unreactive, whereas the alpha particle is reactive. In addition, helium atoms are more stable than alpha particles.
The below infographic presents the differences between helium atom and alpha particle in tabular form for side-by-side comparison.
Summary – Helium Atom vs Alpha Particle
Helium atom or helium chemical element is the atom having the atomic number 2 and chemical symbol He. Alpha particle contains two protons and two neutrons that are bound together into a particle. The key difference between helium atom and alpha particle is that helium atom has two protons, two neutrons, and two electrons, whereas alpha particle only has two protons and two neutrons.
1. “Alpha Radiation.” An Overview | ScienceDirect Topics.