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Helium Symbol

Helium

Helium is element 2 in periodic table with atomic number 2, atomic weight 4.002602, symbol ‘He’, Helium has a Face Centered Cubic structure and Colorless. It is a noble gas element. Trivial name of Helium is noble gases*, aerogens.

Helium Gas

History of Helium

The element Helium was discovered by Pierre Janssen in the year 1895 in Sweden and United Kingdom . Helium derived its name from the Greek word helios, meaning ‘sun’.

Helium is a chemical element with symbol ‘He’ and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among all the elements.

How to Locate Helium on Periodic Table

Periodic table is arranged by atomic number, number of protons in the nucleus which is same as number of electrons. The atomic number increases from left to right. Periodic table starts at top left ( Atomic number 1) and ends at bottom right (atomic number 118). Therefore you can directly look for atomic number 2 to find Helium on periodic table.

Another way to read periodic table and locate an element is by using group number (column) and period number (row). To locate Helium on periodic table look for cross section of group 18 and period 1 in the modern periodic table.

Helium Facts

Name
Hydrogen
Atomic Symbol
He
Atomic Number
2
Atomic Weight
4.002602
Phase
Gas
Colour
Colourless
Classification
other nonmetal
Group in Periodic Table
18
Group Name
helium family or neon family
Period in Periodic Table
1
Block in Periodic Table
p-block
Electronic Configuration
1s2
Melting Point
NA
Boiling Point
-268.93 °C
Electronic Shell Structure
[2]
CAS Number
CAS7440-59-7

Helium Atomic and Orbital Properties

Helium atoms have 1 electrons and the electronic shell structure is [1] with Atomic Term Symbol (Quantum Numbers) 2S1/2.

Helium Atomic Structure
Helium Isotopes

Properties

Atomic Structure of Helium

Atomic Number
2
Atomic Radius
31 pm (0.31 Å)
Number of Electrons (with no charge)
2
Atomic Volume
22.4235406162 cm3
Number of Protons
2
Covalent Radius
32 pm (0.32 Å)
Mass Number
4
Van der Waals Radius
140 pm
Number of Neutrons
2
Neutron Cross Section
0.007 σa/barns
Shell structure (Electrons per energy level)
[2]
Electron Configuration
1s2
Valence Electrons
1s2
Oxidation State

Ground State Electronic Configuration of Helium – neutral Helium atom

The ground state electronic configuration of Neutral Helium atom is 1s2. The portion of Helium configuration that is equivalent to the noble gas of the preceding period, is abbreviated as 1s2]. For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used.This is important as it is the Valence electrons 1s2, electrons in the outermost shell that determine the chemical properties of the element.

Unabbreviated electronic configuration of neutral Helium

Complete ground state electronic configuration for the Helium atom, Unabbreviated electronic configuration

1s2

Atomic Spectrum of Helium

Atomic Spectrum of Helium