Chemistry - Electronegativity
Another quantity that may be linked with core charge values is
electronegativity . Given that the electronegativity of an element is a
measure of the ability of its atoms to attract electrons, it would seem
logical that the stronger the attraction for the outer-shell electrons from
the nucleus the more likely it is that the atom will attract electrons from
Since core charge increases across a period, it follows that
electronegativity will increase across a period.
There is much evidence to support this claim.
Consider the elements in period 3. Na, Mg and Al are all metals. They lose
electrons to form Na, Mg and Al ions respectively. Clearly, these atoms
have low electronegativity.
Si and P, however, form covalent bonds through attracting and sharing the
electrons of other atoms. S and Cl form covalent bonds and Sand Cl ions
respectively. So great is the electron-attracting ability of these last two
elements that they take electrons from other atoms. In the case of NaCl,
consisting of Naand Cl ions, the electronegativity difference between Na
and Cl atoms is so great that electrons are transferred from Na atoms to Cl
Further study of period 3 supports the claim that metals have low
electronegativity and non-metals have moderate to high electronegativity.
This is also consistent with the trend from metal to non-metal across a
period of the periodic table.
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