Ionization power Trends in the periodic Table

The ionization power of an atom is the quantity of energy required to remove an electron from the gaseous type of the atom or ion.

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1st ionization power - The energy required to eliminate the highest power electron from a neutral gas atom.

For Example:

Na(g) → Na+(g)+ e-I1 = 496 kJ/mol

Notice that the ionization power is positive. This is because it requires power to remove an electron.

2nd ionization power - The power required to eliminate a second electron from a singly fee gaseous cation.

For Example:

Na+(g)→ Na2+(g)+ e-I2 = 4560 kJ/mol

The second ionization power is nearly ten times the of the first because the variety of electrons causing repulsions is reduced.

3rd ionization power - The power required to remove a third electron indigenous a double charged gaseous cation.

For Example:

Na2+(g)→ Na3+(g)+ e-I3 = 6913 kJ/mol

The 3rd ionization power is even greater than the second.


Successive ionization energies rise in magnitude because the number of electrons, which reason repulsion, steadily decrease. This is no a smooth curve over there is a huge jump in ionization energy after the atom has actually lost that valence electrons. An atom that has the same digital configuration together a noble gas is yes, really going to host on to its electrons. So, the quantity of power needed to eliminate electrons beyond the valence electron is significantly greater 보다 the power of chemical reactions and bonding. Thus, only the valence electrons (i.e., electrons external of the noble gas core) are involved in chemistry reactions.

The ionization energies the a details atom rely on the mean electron street from the nucleus and also the efficient nuclear charge

These components can be depicted by the adhering to trends:


1st ionization energy decreases under a group.

This is because the highest energy electrons are, top top average, farther native the nucleus. Together the major quantum number increases, the size of the orbital increases and also the electron is much easier to remove.


I1(Na) > I1(Cs)

I1(Cl) > I1(I)

1st ionization energy increases throughout a period.

This is since electrons in the same primary quantum shell do not totally shield the enhancing nuclear fee of the protons. Thus, electrons space held an ext tightly and also require an ext energy to be ionized.


I1(Cl) > I1(Na)

I1(S) > I1(Mg)

The graph the ionization energy versus atomic number is no a perfect line since there are exceptions come the rules that are conveniently explained.


Filled and half-filled subshells display a little increase in stability in the same way that to fill shells show increased stability. So, when trying to remove an electron from among these filled or half-filled subshells, a slightly greater ionization power is found.

Example 1:


I1(Be) > I1(B)

It"s harder come ionize one electron native beryllium than boron since beryllium has a fill "s" subshell.

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Example 2:


I1(N) > I1(O)

Nitrogen has actually a half-filled "2p" subshell so the is harder to ionize one electron from nitrogen than oxygen.