2nd Ionization Energy

By:Jonah Landau, David Miron, and Julie

Baldassano

Quantity of energy that an isolated, gaseous

atom must absorb to discharge a second electron

Energy required to remove an electron from an atom with a +1 charge

Mg+(g)→ Mg2+(g) + e-      I2= 1451kJ/mol

 I1 < I2 < I3 < ... < In

Definition

Generally, the 2nd ionization energy increases from left to right and from bottom to top, with the top right (He) being the highest

Alkali metals are separate, with the same trend of increasing from bottom to top

http://www.webelements.com/periodicity/ionisation_energy_2/

Description of Trend

Atomic radius decreases (left to right and bottom to top),

causing the amount of energy needed to break an electron out of orbit increase from left to right and bottom to top. The smaller the atomic radius, the closer the outer electrons

are to the nucleus and more attracted to the center.

Generally, Second ionization energy is greater than the first. This is because after the first ionization, most atoms become

more like a noble gas in their configuration. It is extremely difficult to remove an electron from a full valence shell.

Reasons for Trend

2nd ionization energy is measured in kilo

joules (kJ) (or electron volts (eV)).

There were two main methods that scientists used to calculate the ionization energy; the subtraction method, and Koopman’s theory.

How 2nd Ionization Energy is Measured

The subtraction method: The first step in this

method is to find the ion are looking to find. Next, you would have to subtract the energy value of the neutral atom, hence the “subtraction” method. This is the ionization energy for that ion.

Koopman’s Theory: This method involves the HOMO or highest occupied molecular orbital. It states that an atom of molecule’s ionization energy is equal to the energy of the orbital from which the electron is ejected, meaning HOMO is equal to the ionization energy. Formal equation: I = -E (I is the orbital the e- is ejected

from).

How 2nd Ionization Energy is Measured

Alkali metals are dramatically larger than the

next groups going over, which goes against the trend, saying that the elements on the left should be smaller.

It requires extra energy to lose a second electron from a filled s (lithium) or p (all the others) shell.

Anomalies in Trend

Be B should increase (left to right) but

actually decreases. Be = 899.5 kJ/mole, and B = 800.7 kJ/mole. Be

has a full 2s subshell. It is stable and wants to stay that way. It is easier to remove the 2p electron from the B atom than an electron from the full 2s subshell of Be.

H Li should decrease (up to down) but actually it increases H is –kJ/mol while Li is 7298 kj/mol. A normal

switch would be something like Be to Mg with Be being 1757 kJ/mol and Mg being 1450 kJ/mol.

Anomalies in Trend

"Ionization Energy: 2nd: Periodicity." WebElements

Periodic Table of the Elements. WebElements, n.d. Web. 30 Oct. 2013.

J.A. Dean (ed) in Lange's Handbook of Chemistry, McGraw-Hill, New York, USA, 14th edition, 1992.

"Second, Third, Fourth, and Higher Ionization Energies." Ionization Energy and Electron Affinity. Purdue, n.d. Web. 30 Oct. 2013.

"Periodic Table Trends." Periodic Table Trends. TAM, n.d. Web. 03 Nov. 2013.

 "Ionization Energy." Ionization Energy. N.p., n.d. Web. 03 Nov. 2013.

Works Cited