When you encounter helium, you are almost always dealing with a neutral atom. A neutral atom has an equal number of positively charged protons in its nucleus and negatively charged electrons orbiting it, resulting in no net electrical charge. Conversely, an ion is an atom or molecule that has gained or lost one or more electrons, giving it a net positive or negative electrical charge. For helium to become an ion, it must be subjected to specific, high-energy conditions that overcome its natural stability. In the vast majority of terrestrial environments, helium remains electrically neutral.
The Neutral Atom: Helium’s Stable Structure
Helium is the second element, meaning its nucleus contains two protons. A neutral helium atom has two orbiting electrons, perfectly balancing the two positive charges. This arrangement is the source of helium’s stability and chemical inertness.
The electrons occupy the lowest possible energy level, the first electron shell. This shell has a maximum capacity of two electrons, making the helium atom’s outer shell completely full.
Because its electron arrangement is energetically favorable, helium belongs to the noble gases. This means the atom is highly unreactive and generally will not combine with other atoms to form molecules. Helium exists in nature as a single, isolated, neutral atom. Forcing it to gain or lose an electron requires a significant input of energy.
How Helium Becomes an Ion
The process of turning a neutral helium atom into a charged particle is called ionization, which requires overcoming its extreme stability. The energy needed to remove the first electron, known as the first ionization energy, is the highest of any element on the periodic table (24.59 eV). This high value occurs because the two electrons are tightly bound by the nucleus’s two protons.
This energy input must be delivered by extreme means, such as intense heat, a powerful electrical discharge, or high-energy radiation like X-rays. If sufficient energy is supplied, one electron can be stripped away, creating a singly ionized helium atom, represented as He+. This ion has two protons and only one electron, resulting in a net positive charge of +1.
If even more energy is delivered, the final electron can be removed. The energy required for this, the second ionization energy, is even higher, at 54.42 eV. Removing both electrons results in a doubly ionized helium atom (He++). This particle is the bare helium nucleus, containing two protons and typically two neutrons. It is commonly known as an alpha particle in nuclear physics, and this transition requires conditions far beyond those found in normal Earth environments.
Where Ionized Helium Exists
Ionized helium exists primarily in environments where energy levels are high enough to continuously strip electrons from the atoms. The most common place to find ionized helium is in plasma, often referred to as the fourth state of matter. Plasma is an ionized gas that contains a high concentration of charged particles.
Vast quantities of He++ exist in stars, such as the Sun, where intense heat and pressure keep matter in a plasma state. Nuclear fusion, which converts hydrogen into helium, creates a constant supply of energetic alpha particles. The solar wind, a stream of charged particles emitted from the Sun’s upper atmosphere, also contains ionized helium.
On Earth, ionized helium is produced in controlled, high-energy settings. It is found in fusion research reactors, where scientists attempt to harness stellar energy. Laboratory experiments, such as those using mass spectrometers or gas discharge lamps, intentionally create helium ions for study. In contrast, the helium extracted from natural gas wells for commercial uses is in its neutral, gaseous form.