Video Transcript
Which of the following elements has
the lowest value of electronegativity according to the Pauling scale? (A) S, (B) Si, (C) Al, (D) Cl, (E)
Mg.
Electronegativity is the tendency
of an atom to attract the shared electrons of a bond. We can use the location of elements
on the periodic table to get a general sense of their relative electronegativity
values. Electronegativity generally
increases going from left to right across the periodic table as well as up a
group. The elements given in the question
are all found in the third period of the periodic table. Based on the periodic trend for
electronegativity, we should expect magnesium to have the lowest electronegativity
and chlorine to have the highest. We can get an idea as to why this
might be the case by looking at an atom of each of these elements.
Atoms of each of these elements
have the same number of electron shells and the same number of innermost
electrons. Electrons in a shared bond with
each of these atoms will experience a similar force of repulsion due to the
innermost electrons. These atoms differ in their number
of protons, with magnesium having the fewest and chlorine having the greatest. The protons in an atom of chlorine
will more strongly attract the shared electrons of a bond than the protons in an
atom of magnesium. So, chlorine has the highest
effective nuclear charge and should therefore have the highest value of
electronegativity, while magnesium has the lowest effective nuclear charge and
should therefore have the lowest value of electronegativity.
Based on effective nuclear charge
and the periodic trend for electronegativity, we believe that magnesium has the
lowest value of electronegativity. But to be sure, we can consult the
Pauling electronegativity scale. The Pauling electronegativity
scale, proposed by Linus Pauling, is a unitless scale that quantifies the
electronegativity of each element. The scale ranges from zero to four,
with zero being the least electronegative and four being the most. If we look at the Pauling
electronegativity values for each element, we find that magnesium does in fact have
the lowest value of electronegativity.
Therefore, of the elements
provided, the element that has the lowest value of electronegativity according to
the Pauling scale is Mg, answer choice (E).
