Atomic Number
2
Element 2
Helium (He)
Helium is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table.
Atomic Mass
4.0026 u
Category
Noble Gas
Period
1
Group
Group 18: noble gases
Phase
gas
Density
0.0001785 g/cm3
Electron Shells
2
Atomic Structure
Protons: 2. Electrons: 2. Neutrons: Varies by isotope.
Electron configuration: 1s²
Why Helium Matters
Helium helps connect atomic number 2, noble gas behavior, period 1 trends, and electron shell structure. Its gas phase, atomic mass of 4.0026 u, and electron configuration 1s² make it useful for comparing bonding patterns across the periodic table.
Discovery and Occurrence
Helium was discovered 1868 by Pierre Janssen, Norman Lockyer. Helium is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table.
Safety and Handling Context
Helium is a noble gas and is generally chemically inert. The main safety concern for many gases is displacement of breathable air in confined spaces.
Related Elements
Frequently Asked Questions
- What is the atomic number of Helium?
- Helium has atomic number 2, which means a neutral atom has 2 protons and 2 electrons.
- What is the chemical symbol for Helium?
- The chemical symbol for Helium is He.
- What category is Helium in?
- Helium is classified as a noble gas and sits in period 1 of the periodic table.
Explore Helium in 3D
Use the interactive table above to rotate atomic models, compare periodic trends, and move from Helium to neighboring elements without losing your place.