Video Transcript
Which of the energy levels below
shows the change in electronic configuration from a sulfur atom, 32 S 16, to a
sulfur two minus ion?
In this question, we are told that
a neutral sulfur atom changes to a negative sulfur ion. To determine the way the electronic
configuration of sulfur would change, we must understand the formation of a negative
ion. Generally, when a negative ion is
formed, a nonmetal atom gains electrons. This occurs so that the nonmetal
atom will attain the electronic configuration of a noble gas. All of the diagrams given in the
answer choices show the positively charged center of the atom called the
nucleus. Then, they illustrate the energy
levels ordinarily found outside of the nucleus. These energy levels are ordered
using capital letters. The numbers written on the bottom
of the diagrams show the amount of electrons present in each energy shell. The sulfur atom will gain electrons
to achieve a noble gas configuration.
Let’s have a look at some
electronic configurations of noble gases.
Helium, atomic number two, will
have two electrons in energy level K. Neon, atomic number 10, will have
two electrons in the K level and eight electrons in the L level. Argon, atomic number 18, will have
two electrons in K, eight electrons in L, and eight electrons in level M. Let’s keep these in mind as we have
a look now at sulfur.
We’ll start by comparing the atom
diagrams to the electronic configuration for a neutral sulfur atom. We are given the symbol for sulfur
in the question. The bottom left number in the
symbol represents the atomic number of sulfur. The atomic number tells us the
number of protons a sulfur atom contains in its nucleus. As a neutral atom, sulfur will also
contain the same number of electrons. Therefore, a sulfur atom will have
a total of 16 electrons.
Energy level K will hold the first
two electrons. The next energy level L will hold
the next eight electrons in the sulfur atom. With only six electrons remaining,
they will all be found in energy level M. Let’s compare this to the diagrams
given for the sulfur atom in the answer choices. We can see that answer choices (A)
and (C) do not have the correct configurations for a sulfur atom, so we can
eliminate them.
Let’s now deduce how the diagram of
a sulfur two minus ion would look.
We are told the charge of the
sulfur ion will be two minus, so we know it will have two more electrons than
protons. When we add 16 and two, we get
18. A neutral sulfur atom with 16
electrons has 6 electrons in the M energy level. With two more, it will have eight,
giving it a two minus charge. The sulfur ion achieves the noble
gas electronic configuration of argon. Let’s have a look at the remaining
ion energy level diagrams.
We can see that answer choice (D)
matches the correct energy level diagrams for both the neutral sulfur atom and the
negative sulfur ion. Therefore, the energy levels that
show the change in electronic configuration from a sulfur atom to a sulfur two minus
ion is answer choice (D).
