Ionization Energy and Electronegativity
Date: Fall 2009
What is the relationship between ionization energy and
electronegativity, are they inversely related, or unrelated?
There are some general trend relationships between ionization energy
and electronegativity. In general, since the first ionization energy
tends to increase as you go left to right along a period (row), and
electronegativity does the same - we say that they follow the same
trend. Similarly as you go from top to bottom of a group (column),
both first ionization energy and electronegativity decreases, again
we say that they follow the same trend.
However, we do have to be a bit careful with this. This is a
*trend*. This means that there are some variations, a few exceptions
that do not fit the trend. In general though, we can say that they
are directly related.
Another important point is that, ionization energy is an actual set
of data that is determined experimentally. Electronegativity is a
derived information based on many different data only one of which
is ionization energy.
Greg (Roberto Gregorius)
These two characteristics of an element are related, but not absolutely.
The first ionization energy is the energy required to remove one electron from a
gaseous neutral atom (it is usually given as a value per mole of atoms). The more
strongly the outer electron that would be removed in ionization is attracted to the
nucleus, the more energy is required. The more repulsion from other electrons in the
atom, the less energy is required.
Electronegativity is the ability for the atom to attract electrons in a chemical
bond. It is measured on the Pauling scale where F = 4.0 (the most electronegative).
I'm sure that you can see that these two are related. If it takes more energy to
remove an electron from an atom then the nucleus of that atom has a strong attraction
to the outer electrons and will therefore have a strong attraction to electrons in any
bond the atom is involved with, so the atom will also be electronegative.
The relationship is fairly clear and you could show this by plotting electronegativity
vs 1st ionization energy for all the elements you can find data on.
The term ionization energy (EI) (of an atom or molecule) is most commonly
used to refer to the energy required to remove (to infinity) the outermost
electron in the atom or molecule when the gas atom or molecule is isolated
in free space and is in its ground electronic state. This quantity was
formerly called ionization potential, and was at one stage measured in
Electronegativity, symbol ÷, is a chemical property that describes the
ability of an atom (or, more rarely, a functional group) to attract
electrons (or electron density) towards itself in a covalent bond. An
atom's electronegativity is affected by both its atomic weight and the
distance that its valence electrons reside from the charged nucleus. The
higher the associated electronegativity number, the more an element or
compound attracts electrons towards it.
So it does not look like either are dependent (related to) on the other.
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Update: June 2012