hello and welcome to the chemistry
solution this tutorial is on effective
nuclear charge
although negatively charged electrons
and atoms are attracted to the
positively charged nucleus there at the
same time repelled by other electrons in
the atom and so the effective nuclear
charge is the average nuclear charge
felt by an individual electron in an
atom taking into consideration the
shielding effect of inner shell
electrons and we'll explore in more
detail what that means as we go through
this tutorial the effective charge is
equal to Z minus s where Z is the number
of protons in the nucleus and s is the
number of inner shell electrons now
remember the number of protons in the
nucleus is the same as the atomic number
and can be easily determined by using
your periodic table in this tutorial
we'll go through how to determine the
number of inner shell electrons let's
look at an example what is the effective
nuclear charge felt by an electron in
the N equals 3 shell of sulphur remember
that the effective charged is equal to
the number of protons in the nucleus
minus the number of inner shell
electrons the atomic number of sulphur
is 16 and that means sulphur has 16
protons in the nucleus now let's start
diagramming the electrons around the
nucleus of sulphur remember that for a
neutral atom the number of electrons is
equal to the number of protons and so a
neutral sulphur atom has 16 electrons
remember that the N equals 1 shell of
sulphur can hold two electrons we now
need to place 14 more electrons around
the nucleus of sulphur the N equals 2
shell can hold 8 electrons so now we've
diagrammed 10 electrons the N equals 3
shell can hold 14 electrons total but
because sulphur only has 16 electrons
and we've already diagrammed 10 of them
there will only be 6 electrons remaining
to put into the N equals 3 shell
now the question is asking us what the
effective nuclear charge is felt by an
electron in the N equals 3 shell that
means that both the N equals 2 and N
equals 1 shells are inner shells and so
the number of inner shell electrons is
equal to 10
this makes the effective charge for an
electron in the N equals 3 shell of
sulfur equal to 6 now whenever you are
looking for the effective nuclear charge
felt by an electron in the outermost
shell of an atom and in Sulphur the
outermost shell is the N equals 3 shell
the effective charge will always be
equal to the group number on the
periodic table but in some cases you'll
be asked to find the effective charge
for an electron not in the outermost
shell so let's go through how we would
do that and we're going to use pretty
much the same method what is the
effective nuclear charge felt by an
electron in the N equals 2 shell of
chlorine a neutral chlorine atom has 17
protons and 17 electrons for this
example I'm going to show you another
way to diagram out the electrons so you
don't have to draw an elaborate picture
each time remember that the N equals 1
shell can hold two electrons the N
equals 2 shell can hold 8 electrons so
now we have 7 electrons left 17 minus 8
minus 2 that means in the N equals 3
shell there will be 7 electrons even
though total N equals 3 shell could hold
14 now remember that Z is equal to the
atomic number of chlorine which is equal
to the number of protons which is 17 and
s is the number of inner shell electrons
remember that the inner shells are
between the shell of interest and the
nucleus of the atom and in this case
because we're looking for the effective
nuclear charge fault by an electron in
the N equals 2 shell the only inner
shell electrons will be in the N equals
1 shell and there are only two of them
this means that the effective nuclear
charge felt by an electron in the N
equals 2 shell of chlorine is equal to
15
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solution we hope you enjoyed this
tutorial
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