Electron Orbitals and Configurations: Lecture Summary and Key Concepts

Name: More on Orbitals and Electron Configuration
Uploaded: 2015-05-07T14:26:20+00:00
Duration: 14 min 30 s
Channel: Saylor University
Description: Summary and key takeaways on More on Orbitals and Electron Configuration: Summary & Key Takeaways, covering The Nature of Orbitals Electrons do not travel in

Saylor University

May 07, 2015

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14 min video

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1 min read

YouTube video ID: HKQCdYgz45g

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Electrons do not travel in simple circular paths; they exist as probability density functions around the nucleus. An orbital marks the region where there is a high chance of locating an electron, and diagrams typically outline the volume that contains the electron 90 % of the time. This probabilistic view replaces the outdated Bohr model of fixed orbits.

Filling Energy States

Electrons occupy orbitals beginning with the lowest energy level. The 1s orbital, a spherical region, holds two electrons; once it is full, additional electrons move to the next higher energy state, such as the 2s orbital. Higher shells are added as concentric layers, each with its own set of orbitals that follow the same two‑electron capacity rule.

P‑Orbitals and Visualization

P‑orbitals possess a dumbbell shape and appear in three mutually perpendicular orientations: pₓ (left/right), p_y (forward/backward), and p_z (up/down). These shapes correspond to standing‑wave patterns that indicate where the probability of finding an electron is greatest within the subshell. The three p‑orbitals together can accommodate six electrons, and their filling follows the same energy‑order principle, with Hund’s rule governing the distribution among degenerate orbitals.

Determining Electron Configuration

The periodic table is organized to reflect the sequential filling of s, p, and d orbitals. To write an element’s electron configuration, locate its period (row) and block (s or p), then count electrons from the lowest energy orbital upward, ensuring the total number of electrons matches the atomic number. For example, hydrogen is 1s¹, helium is 1s², lithium adds a 2s¹ electron, nitrogen fills to 1s² 2s² 2p³, and silicon completes to 1s² 2s² 2p⁶ 3s² 3p².

Takeaways

Orbitals are probability density functions that define where an electron is likely to be found, typically visualized as the region containing the electron 90 % of the time.
Electrons fill orbitals from the lowest to higher energy levels, with each orbital holding a maximum of two electrons.
P‑orbitals have a dumbbell shape in three orientations (pₓ, p_y, p_z) and represent the highest‑probability regions for electrons in that subshell.
The periodic table maps directly onto orbital filling order, allowing electron configurations to be derived by counting electrons across periods and blocks.
A correct electron configuration must have superscript totals that equal the element’s atomic number, confirming charge neutrality for a neutral atom.

Frequently Asked Questions

What does the 90% probability boundary mean for an orbital?

The 90% probability boundary marks the surface that encloses the region where an electron is expected to be found 90 % of the time. It provides a visual limit for orbital diagrams, helping illustrate the most likely space an electron occupies without implying a fixed path.

How does the periodic table help determine electron configurations?

The periodic table arranges elements so that their positions reflect the order in which s, p, and d orbitals fill. By identifying an element’s period and block, one can count electrons from the lowest energy orbital upward, ensuring the total matches the atomic number and yielding the correct configuration.

Who is Saylor University on YouTube?

Saylor University is a YouTube channel that publishes videos on a range of topics. Browse more summaries from this channel below.

Does this page include the full transcript of the video?

Yes, the full transcript for this video is available on this page. Click 'Show transcript' in the sidebar to read it.

Helpful resources related to this video

If you want to practice or explore the concepts discussed in the video, these commonly used tools may help.

Molecular Model Kit For Chemistry Students Recommended

Provides a physical, 3D way to visualize atomic structures and orbital geometries, helping students grasp the concepts of s and p orbitals.

Amazon →

Large Laminated Periodic Table Of Elements

Serves as a constant reference tool for determining electron configurations and identifying orbital blocks as described in the lecture.

Amazon →

General Chemistry Textbook With Orbital Diagrams

Offers detailed illustrations and written explanations of probability density functions and electron filling rules to reinforce the lecture content.

Amazon →

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Full Transcript YouTube

in the last few videos we learned that
the configuration of electrons in an
atom aren't in kind of the simple
classical Newtonian orbit configuration
and that's the bore model of the
electron and I'll just keep reviewing it
just because I think it's an important
point if that's the nucleus remember
it's just a tiny tiny tiny dot if you
think about the entire volume of the
actual atom and instead of the electron
being in kind of orbits around it which
would be how a how a planet orbits the
Sun so instead of being orbits around it
it's described by orbitals which are
these probability density functions so
an orbital let's say that's the
nucleus it would describe if you took
any point in space around the nucleus
the probability of finding the electron
so actually any volume of of any volume
of space around the nucleus it would
tell you the probability of finding the
electron within that volume and so if
you were to just take a bunch of
snapshots of electrons uh let's say in
the 1 s orbital and that's what the 1 s
orbital looks like it's just a little
it's a it's a you can barely see it
there but it's a sphere around the
nucleus and that's the lowest energy
state that an electron can be in if you
were to just take a number of snapshots
of electrons let's say you were take a
number of snapshots of helium which has
two electrons both of them are in the 1
s orbital it would look like this if you
took one snapshot maybe it'll be there
the next snapshot maybe like electron is
there then the electron's there then the
electron is there then it's there and if
you kept doing the snapshots you would
have a bunch of them really close and
then it gets a little bit sparser as you
get out as you get further and further
out away from the electron but you see
it was you're much more likely to find
the electron close to the center of the
of the of the atom than further out
although you might have had an
observation with the electron sitting
all the way out there or sitting over
here so it really could have been
anywhere but if you take multiple
observations you'll see what that
probability function is describing it's
it's saying look there's a much lower
probability of finding the electron out
in this little cube of volume space and
it is in this little cube of volume
space and when you see these diagrams
that draw this orbital like this let's
say they draw it they draw it like a
shell like a sphere and I'll try to make
it look threedimensional so let's say
this is the outside of it and then the
nucleus sitting someplace in the inside
they're just saying what where they just
are cut off where can I find the
electron 90% of the time so they're
saying okay I can find the electron 90%
of the time within this circle if I were
to do the cross-section but every now
and then the electron can show up
outside of that right because it's all
probabilistic so this can still happen
you can still find the electron if this
is the orbital we're talking about out
here right and then we in the last video
we said okay the electrons fill up the
orbitals from lowest energy State low
low
energy to high energy state to high
energy State I mean you could imagine it
you know if I'm if I'm playing Tetris
well I don't know if Tetris is a thing
but if I'm stacking cubes I I lay out
cubes from low energy if this is the
floor I put the first Cube at the lowest
energy State and let's say I can't put
cubes and let's say I could put the
second Cube at a low energy State here
but I only have that much whoops I only
have I only have this much space here to
work with so I have to put the third
Cube at the next highest energy state in
this case our energy would be described
as potential energy right this is just a
classical Newtonian physics example but
that's the same idea with with electrons
once I have two electrons in the in this
one s orbital so let's say the electron
configuration of helium is 1 S2 the
third electron I can't put any put there
anymore because there's only room for
two electrons and the way I think about
it is these two electrons are not going
to repel the third one I want to add so
then I have to go to the 2s orbital and
now if I were to plot the 2s orbital on
top of this one it would look something
like this where I have a high
probability of finding the electrons in
this shell that's essentially around the
ons
orbital right so and right now if I'm
maybe I'm dealing with I'm dealing with
lithium right now so I only have one
extra electron so this one extra
electron that might be where I observed
that extra electron but every now and
then it could show up there it could
show up there it could show up there but
the high probability is there so when
you say where is where is it going to be
90% of the time it'll be like this shell
that's around the center remember when
it's threedimensional you would kind of
cover it up so it' be this shell but so
that's what they drew here I don't know
if you can barely they Dre the 1s is
just a red shell and then the 2s the in
the second energy shell is just this
blue shell over it you can see it a
little bit better in actually the higher
energy orbits the higher energy shells
where the seventh s energy shell is this
red area and then you have the Blue Area
then the red and the blue and so I think
you get the idea each of those are
energy shells so you kind of keep
overlaying the S orbitals around each
other but you probably see this other
stuff here and the general principle
remember is that the the electrons fill
up the orbital from lowest energy
orbital to higher energy orbital so the
first one that's filled up is the 1 s
this is the one this is the S so this is
the 1 s it can fit two electrons then
the next one that's filled up is 2s it
can fill two more electrons and then the
next one and this is where it gets
interesting you fill up the 2p orbital
the 2p orbital that's this right here 2
p orbitals and notice the P orbitals
have something p subz p subx p sub y and
then you're what does that mean well if
you look at the P orbitals they have
these these dumbbell shapes and they
look a little unnatural but I think in
in future videos we'll show you how
they're they're analogous to standing
waves but if you look at these there's
three ways that you can configure these
dumbbells one in the Z Direction up and
down one in the X Direction left to
right and then one in the Y Direction
This Way forward and backwards right and
so if you were to draw let's say you
wanted to draw the the P orbitals so
let's say so this this is what you fill
next and actually you fill one electron
here then another electron here then
another electron there then you fill
another electron we'll talk about spin
and things like in the future but there
there and there and that's actually
called Huns rule but we'll maybe I'll do
a whole video on Huns rule but that's
not relevant to a first year chemistry
lecture but it fills in that order and
once again I I I want you to have the
intuition of what this what this would
look like look I should put look in in
in quotation marks because it's it's
very abstract but if you wanted to
visualize the P orbitals let's say we're
looking at the electron configuration
for let's say for
carbon so the electron configuration for
carbon the first two electrons go into
so 1 S1 1 S2 so then it fills sorry you
can't see everything so it fills the 1s2
so carbon's
configuration so
carbon it fills 1 S1 then 1
S2 and this is just the configuration
for helium then it goes to the second
shell which is the second period right
that's why it's called the periodic
table we'll talk about periods and
groups in the future and then you go
here so this is filling the S the 2s
we're in the second period right here
that's the second period see one two
have to go off the so you can see
everything so it fills these two so 2 S2
and then it starts filling up the P
orbitals so then it starts filling one p
and then 2 p so and we're still in the
second shell so 2 s 2 2 P2 so the
question is what would this look like if
we just wanted to visualize this orbital
right here the P orbitals so we have two
electrons so one electron is going to be
in the let's say if this is I'll try to
draw some
axes that's too
thin so if I draw a
three-dimensional volume kind of
axes if I were to make one a bunch of
observations of say one of the electrons
in the P orbitals let's say in the pz
dimension sometimes it might be here
sometimes it might be there sometimes it
might be there sometimes and then if you
keep taking a bunch of
observations you take a bunch of
observations you're going to have
something that looks
like this Bell shape this barbell shape
right there and then for the other
electron that's in maybe in the X
Direction you make a bunch of
observations let me do in a different in
a noticeably different color it'll look
like this you take a bunch of
observations say wow you know it's it's
a lot more likely to find that electron
in kind of the dumbbell in that dumbbell
shape but you could find it out there
you could find it there you could find
it there this is just a probability much
higher probability of finding it in here
than out here and that's the way that
that's the best way I can think of to
visualize it now what we were doing here
this is called an electron configuration
and the way to do it and there's
multiple ways that are that are taught
in chemistry class but the way I like to
do it is you take the periodic table and
you say okay
these groups when I say groups I mean
the columns these are going to
fill s the s subshell or the S orbitals
these over here are going you can just
write s up here just right there these
over here are going to fill the P
orbitals
actually let me take helium out of the
picture the P orbitals let me just do
that let me take helium out of the
picture these take the P orbitals and
actually for the sake of figuring out
these you should take helium and and
throw it right over there right the
periodic table is just a way to organize
things so it makes sense but in terms of
trying to figure out orbitals you could
take helium let me do that the magic of
computers cut it out and then let me
paste it right over
there right and now you see that helium
you get 1 s then you get 2s so helium's
configuration is sorry you get 1 S1 then
1 S2 we're in the First Energy
shell right so the
configuration of
hydrogen the configuration of
hydrogen is 1 S1 you only have one
electron in the in the S subshell of the
one of the first energy shell the
configuration of helium is 1
S2 and then you go you fill you start
filling the second energy shell the
configuration of
lithium lithium is 1 S2 that's where the
first two electrons go and then the
third one goes into
2s1 right and then I think you start to
see the pattern and then when you go to
nitrogen you say okay it has three in
the p in the P sub orbital so you can
almost start backwards right so two this
is we're in Period two right so this is
2
P3 right let me write that down so I
could write that down first 2
P3 so that's where those kind of the
last three electrons that go into the p
orbital then it'll have these two that
go into the two S2 orbital 2 S2 orbital
and then at the first two or the the
kind of the electrons in the lowest
energy state will be 1 S2 so this is the
electron configuration right
here of nitrogen of nitrogen and just to
make sure you did your your
configuration right what you do is you
count the number of electrons so 2 + 2
is 4 + 3 is 7 and we're talking about
neutral atoms so the electrons should
equal the number of protons the atomic
number is the number of protons so we're
good 7 proton so this is so far when
we're dealing just with the S's and the
PS this is pretty straightforward if I
wanted to figure out the configuration
of
silicon right there what is it well
we're in the third period one 2 three
that's just the third row so it's start
and this is the P block right here so
this is the second row in the P block
right one two 3 4 five 6 right we're in
the second row of the P block so we
start off with three 3
P2 3
P2 and then we have 3 S2 3 S2 and then
it filled up all of this P block over
here so it's 2 P6 2 P6 and then here 2
S2 and then of course it filled up the
first shell before it could fill up
these other shells so 1 S2 so this is
the electron
configuration for silicon and if we can
confirm that we should have 14 electrons
2 + 2 is 4 + 6 is 10 10 + 2 is 12 + 2
more is 14 so we're good with silicon I
think I'm running low on time right now
so in the next video we'll start
addressing what happens when you Cod to
these elements or the d block and you
can kind of already guess what happens
we're going to start filling up these D
orbitals these D orbitals here that have
even more bizarre shapes and the way I
think about it this just not to waste
too much time is that as you go further
and further out of the electron out from
the nucleus there's more space in
between the lower energy orbitals to
fill in more of these Bizarro shaped
orbitals but that these are kind of the
the balance well we'll talk about
standing waves in the future but these
are kind of the balance between trying
to get close to the nucleus and the
proton and those positive charges
because the electron charges are
attracted to them while at the same time
avoiding the other electron charges or
at least their Mass distribution
functions anyway see you in the next
video so

Filling Energy States

P‑Orbitals and Visualization

Determining Electron Configuration

Takeaways

Frequently Asked Questions

What does the 90% probability boundary mean for an orbital?

How does the periodic table help determine electron configurations?

Who is Saylor University on YouTube?

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