Helium – Electron Affinity – Electronegativity – Ionization Energy of Helium

Electron Affinity and Electronegativity of Helium

Electron Affinity of Helium is — kJ/mol.

Electronegativity of Helium is .

First Ionization Energy of Helium is 24.5874 eV.

Electron Affinity

In chemistry and atomic physics, the electron affinity of an atom or molecule is defined as:

the change in energy (in kJ/mole) of a neutral atom or molecule (in the gaseous phase) when an electron is added to the atom to form a negative ion.

X + e → X + energy        Affinity = – ∆H

Helium - Electron Affinity - Electronegativity - Ionization Energy
In other words, it can be expressed as the neutral atom’s likelihood of gaining an electron. Note that ionization energies measure the tendency of a neutral atom to resist the loss of electrons. Electron affinities are more difficult to measure than ionization energies.

An atom of Helium in the gas phase, for example, gives off energy when it gains an electron to form an ion of Helium.

He + e → He        – ∆H = Affinity = — kJ/mol

Electron affinity is one of the most important parameters that guide chemical reactivity. Molecules with high electron affinity form very stable negative ions which are important in the chemical and health industry as they purify the air, lift mood, and most importantly, act as strong oxidizing agents. To use electron affinities properly, it is essential to keep track of signs. When an electron is added to a neutral atom, energy is released. This affinity is known as the first electron affinity, and these energies are negative. By convention, the negative sign shows a release of energy. However, more energy is required to add an electron to a negative ion which overwhelms any release of energy from the electron attachment process. This affinity is known as the second electron affinity, and these energies are positive.

Halogens have the highest electron affinities among all elements. In fact, the electron affinity of Cl, 3.62 eV is the largest of all the elements. Superhalogens are molecules that have electron affinities (EA) greater than that of Cl, the element with the highest EA (3.62 eV).

It is well known that noble gases have closed electronic shell structure and hence have high ionization potentials and low electron affinities, due to which they are chemically inert and resistant to salt formation under most conditions.

Affinities of Nonmetals vs. Affinities of Metals

  • Metals: Metals like to lose valence electrons to form cations to have a fully stable shell. The electron affinity of metals is lower than that of nonmetals. Mercury most weakly attracts an extra electron.
  • Nonmetals: Generally, nonmetals have more positive electron affinity than metals. Nonmetals like to gain electrons to form anions to have a fully stable electron shell. Chlorine most strongly attracts extra electrons. The electron affinities of the noble gases have not been conclusively measured, so they may or may not have slightly negative values.

Learn more about electron affinities.

Electronegativity

Electronegativity, symbol χ, is a chemical property that describes the tendency of an atom to attract electrons towards this atom. For this purpose, a dimensionless quantity, the Pauling scale, symbol χ, is the most commonly used.

The electronegativity of Helium is:

χ = —

In general, an atom’s electronegativity is affected by both its atomic number and the distance at which its valence electrons reside from the charged nucleus. The higher the associated electronegativity number, the more an element or compound attracts electrons towards it.

As it is usually calculated, electronegativity is not a property of an atom alone, but rather a property of an atom in a molecule. Even so, the electronegativity of an atom is strongly correlated with the first ionization energy, and negatively correlated with the electron affinity. Electrons with low ionization energies have low electronegativities because their nuclei do not exert a strong attractive force on electrons. Elements with high ionization energies have high electronegativities due to the strong pull exerted by the positive nucleus on the negative electrons. Therefore the electronegativity is greatest at the top-right of the periodic table and decreases toward the bottom-left.

Caesium is the least electronegative element (0.79); fluorine is the most (3.98).

Learn more about electronegativities.

 

electron affinity and electronegativity

First Ionization Energy of Helium

First Ionization Energy of Helium is 24.5874 eV.

Ionization energy, also called ionization potential, is the energy necessary to remove an electron from the neutral atom.

X + energy → X+ + e

where X is any atom or molecule capable of being ionized, X+ is that atom or molecule with an electron removed (positive ion), and e is the removed electron.

A Helium atom, for example, requires the following ionization energy to remove the outermost electron.

He + IE → He+ + e        IE = 24.5874 eV

The ionization energy associated with removal of the first electron is most commonly used. The nth ionization energy refers to the amount of energy required to remove an electron from the species with a charge of (n-1).

1st ionization energy

X → X+ + e

2nd ionization energy

X+ → X2+ + e

3rd ionization energy

X2+ → X3+ + e

Ionization Energy for different Elements

There is ionization energy for each successive electron removed. The electrons that circle the nucleus move in fairly well-defined orbits. Some of these electrons are more tightly bound in the atom than others. For example, only 7.38 eV is required to remove the outermost electron from a lead atom, while 88,000 eV is required to remove the innermost electron. Helps to understand the reactivity of elements (especially metals, which lose electrons).

In general, the ionization energy increases moving up a group and moving left to right across a period. Moreover:

  • Ionization energy is lowest for the alkali metals which have a single electron outside a closed shell.
  • Ionization energy increases across a row on the periodic maximum for the noble gases which have closed shells.

For example, sodium requires only 496 kJ/mol or 5.14 eV/atom to ionize it. On the other hand neon, the noble gas, immediately preceding it in the periodic table, requires 2081 kJ/mol or 21.56 eV/atom.

Learn more about ionization energy.

ionization energy

Helium – Properties

Element Helium
Atomic Number 2
Symbol He
Element Category Noble Gas
Phase at STP Gas
Atomic Mass [amu] 4.0026
Density at STP [g/cm3] 0.1785
Electron Configuration 1s2
Possible Oxidation States 0
Electron Affinity [kJ/mol]
Electronegativity [Pauling scale]
1st Ionization Energy [eV] 24.5874
Year of Discovery 1895
Discoverer Ramsey, Sir William & Cleve, Per Teodor
Thermal properties
Melting Point [Celsius scale] -272.2
Boiling Point [Celsius scale] -268.9
Thermal Conductivity [W/m K] 0.1513
Specific Heat [J/g K] 5.193
Heat of Fusion [kJ/mol]
Heat of Vaporization [kJ/mol] 0.0845

 

Helium in Periodic Table

Hydro­gen1H He­lium2He
Lith­ium3Li Beryl­lium4Be Boron5B Carbon6C Nitro­gen7N Oxy­gen8O Fluor­ine9F Neon10Ne
So­dium11Na Magne­sium12Mg Alumin­ium13Al Sili­con14Si Phos­phorus15P Sulfur16S Chlor­ine17Cl Argon18Ar
Potas­sium19K Cal­cium20Ca Scan­dium21Sc Tita­nium22Ti Vana­dium23V Chrom­ium24Cr Manga­nese25Mn Iron26Fe Cobalt27Co Nickel28Ni Copper29Cu Zinc30Zn Gallium31Ga Germa­nium32Ge Arsenic33As Sele­nium34Se Bromine35Br Kryp­ton36Kr
Rubid­ium37Rb Stront­ium38Sr Yttrium39Y Zirco­nium40Zr Nio­bium41Nb Molyb­denum42Mo Tech­netium43Tc Ruthe­nium44Ru Rho­dium45Rh Pallad­ium46Pd Silver47Ag Cad­mium48Cd Indium49In Tin50Sn Anti­mony51Sb Tellur­ium52Te Iodine53I Xenon54Xe
Cae­sium55Cs Ba­rium56Ba Lan­thanum57La 1 asterisk Haf­nium72Hf Tanta­lum73Ta Tung­sten74W Rhe­nium75Re Os­mium76Os Iridium77Ir Plat­inum78Pt Gold79Au Mer­cury80Hg Thallium81Tl Lead82Pb Bis­muth83Bi Polo­nium84Po Asta­tine85At Radon86Rn
Fran­cium87Fr Ra­dium88Ra Actin­ium89Ac 1 asterisk Ruther­fordium104Rf Dub­nium105Db Sea­borgium106Sg Bohr­ium107Bh Has­sium108Hs Meit­nerium109Mt Darm­stadtium110Ds Roent­genium111Rg Coper­nicium112Cn Nihon­ium113Nh Flerov­ium114Fl Moscov­ium115Mc Liver­morium116Lv Tenness­ine117Ts Oga­nesson118Og
1 asterisk Cerium58Ce Praseo­dymium59Pr Neo­dymium60Nd Prome­thium61Pm Sama­rium62Sm Europ­ium63Eu Gadolin­ium64Gd Ter­bium65Tb Dyspro­sium66Dy Hol­mium67Ho Erbium68Er Thulium69Tm Ytter­bium70Yb Lute­tium71Lu
1 asterisk Thor­ium90Th Protac­tinium91Pa Ura­nium92U Neptu­nium93Np Pluto­nium94Pu Ameri­cium95Am Curium96Cm Berkel­ium97Bk Califor­nium98Cf Einstei­nium99Es Fer­mium100Fm Mende­levium101Md Nobel­ium102No Lawren­cium103Lr