4.3 Electron Configurations
Summary
TLDRThis educational video script explains electron configurations in atoms, emphasizing the preference for the lowest energy state. It outlines the Aufbau principle, which directs electron placement starting from 1s to higher energy levels. The Pauli exclusion principle is highlighted, stating no two electrons can share all four quantum numbers identically, affecting their spin states. Hund's rule is also discussed, advocating for single electron occupancy in equal energy orbitals before pairing. The script further illustrates how to represent electron configurations using orbital notation, electron configuration notation, and noble gas notation, simplifying the depiction of atoms' electron structures.
Takeaways
- π¬ Atoms and electrons prefer to be in the lowest energy state possible, with electrons tending to occupy lower energy orbitals first.
- π The Aufbau principle dictates that electrons fill the lowest energy orbitals first, following a specific order: 1s, 2s, 2p, 3s, 3p, and so on.
- π The energy levels don't simply increase sequentially; for example, the 4s sublevel has lower energy than the 3d sublevel.
- π₯ The Pauli exclusion principle states that no two electrons in the same atom can have the same set of four quantum numbers, leading to opposite spins in the same orbital.
- 𧲠Hund's rule asserts that equal energy orbitals must each be occupied by one electron before any can be doubly occupied, minimizing electron repulsion and lowering energy.
- π Orbital notation is a way to represent electron configurations by drawing lines for orbitals and arrows for electrons, indicating their spin states.
- π Electron configuration notation simplifies the representation by using the orbital name with a superscript to show the number of electrons, e.g., 1sΒ² for helium.
- π The highest energy level with electrons is known as the highest occupied energy level, and its electrons are the valence electrons, which are reactive in chemical reactions.
- π Inner shell electrons are those in lower energy levels and are generally unreactive, being 'hidden' by the outer energy levels.
- πΊ Noble gas notation is a shorthand for electron configurations, using the configuration of the preceding noble gas and adding the outermost electrons, making it easier to write configurations for elements beyond the first few periods.
Q & A
What is the primary preference of electrons in atoms?
-Electrons in atoms prefer to be in the lowest energy state possible, which means they tend to occupy the ground state and fill lower energy orbitals first.
What is the Aufbau principle and how does it relate to electron configuration?
-The Aufbau principle states that electrons fill the lowest energy orbitals first, following a specific order: 1s, 2s, 2p, 3s, 3p, and so on, as indicated by increasing energy levels.
Why do electrons fill the 4s orbital before the 3d orbital even though 3d is higher in the periodic table?
-According to the Aufbau principle, the 4s orbital is lower in energy than the 3d orbital, so electrons fill the 4s orbital before the 3d orbital, despite the order in the periodic table.
What does the Pauli exclusion principle state about electrons in an atom?
-The Pauli exclusion principle states that no two electrons in the same atom can have the same set of four quantum numbers, which means that electrons in the same orbital must have opposite spins.
What is Hund's rule and how does it affect the filling of orbitals?
-Hund's rule states that equal energy orbitals must each be occupied by one electron with the same spin before any orbital is doubly occupied, which minimizes electron repulsion and lowers the overall energy of the atom.
How is orbital notation used to represent electron configurations?
-Orbital notation represents electron configurations by drawing lines for orbitals and arrows for electrons, with the arrows indicating the spin state of each electron and the name of the orbital below it.
What is electron configuration notation and how is it different from orbital notation?
-Electron configuration notation is a simpler way to represent electron configurations by writing the name of the orbital with a superscript to indicate the number of electrons in that orbital, as opposed to drawing out each electron and orbital.
What are valence electrons and why are they important in chemistry?
-Valence electrons are the electrons in the highest energy level of an atom, which are involved in chemical reactions. They are important because they determine the reactivity of an element.
What is the significance of the term 'octet' in the context of electron configurations?
-The term 'octet' refers to a complete outer energy level with eight electrons, which is a stable configuration that makes elements unreactive, like those found in the noble gases group of the periodic table.
How does noble gas notation simplify writing electron configurations for elements?
-Noble gas notation simplifies electron configurations by using the electron configuration of the preceding noble gas in brackets, followed by the additional electrons that are unique to the element, thus avoiding the need to write out the entire configuration.
Why are the 1s electrons in an atom considered inner shell electrons?
-The 1s electrons are considered inner shell electrons because they are in a lower energy level and are less involved in chemical reactions, being 'hidden' behind the higher energy levels where valence electrons are located.
Outlines
π¬ Electron Configurations and Energy States
This paragraph introduces the concept of electron configurations, emphasizing that electrons, like the rest of the universe, prefer to be in the lowest energy state possible. It explains that electrons fill orbitals in a specific order, starting with the lowest energy orbitals (1s, 2s, 2p, etc.) and following the Aufbau principle, which dictates that electrons occupy the lowest energy orbitals first. The paragraph also discusses the energy levels of suborbitals, noting that the 3d suborbital is higher in energy than the 4s suborbital. It introduces the Pauli Exclusion Principle, stating that no two electrons in the same atom can have the same set of four quantum numbers, leading to electrons in the same orbital having opposite spins. Lastly, it mentions Hund's Rule, which states that electrons will occupy equal-energy orbitals singly before pairing up to minimize repulsion and maintain lower energy states.
π Representing Electron Configurations
The second paragraph delves into the different ways to represent electron configurations. It starts with orbital notation, which involves drawing lines for orbitals and arrows for electrons, indicating their spin states. The paragraph then moves on to electron configuration notation, a simpler method that uses the orbital name with a superscript to show the number of electrons it contains. Examples are given for hydrogen, helium, and lithium, illustrating how the notation reflects the electron filling process. The concept of valence and inner shell electrons is introduced, with valence electrons being in the outermost energy level and thus more reactive. The paragraph also explains the highest occupied energy level and how it relates to chemical reactivity. A visual representation using color-coded energy levels and suborbitals is briefly mentioned, providing a simplified model for understanding electron configurations.
βοΈ Noble Gas Notation for Electron Configurations
The final paragraph discusses the use of noble gas notation as a shorthand for writing electron configurations, particularly useful for elements beyond helium. It explains that the electron configuration of a noble gas can be used as a base, with additional electrons noted separately. This method simplifies the process of writing electron configurations, as it eliminates the need to write out the full configuration of inner shell electrons. The paragraph uses sodium as an example, showing how its electron configuration can be abbreviated using neon's configuration followed by the additional 3s1 electron. This notation is especially helpful for elements with more complex electron configurations, making it easier to represent and understand their electronic structures.
Mindmap
Keywords
π‘Electron Configurations
π‘Ground State
π‘Aufbau Principle
π‘Pauli Exclusion Principle
π‘Hund's Rule
π‘Orbital Notation
π‘Electron Configuration Notation
π‘Valence Electrons
π‘Inner Shell Electrons
π‘Noble Gas Notation
π‘Octet Rule
Highlights
Atoms and electrons prefer to be in the lowest energy state possible.
Electrons occupy lower energy levels first, such as 1s before 2s, 2p, etc.
The Aufbau principle dictates that electrons fill the lowest energy orbitals first.
Electron configuration follows a pattern: 1s, 2s, 2p, 3s, 3p, with exceptions for higher energy levels.
The Pauli exclusion principle states no two electrons in an atom can have the same set of four quantum numbers.
Electrons in the same orbital must have opposite spins due to the Pauli exclusion principle.
Hund's rule states that equal energy orbitals must each be occupied by one electron before any can be doubly occupied.
Electron configurations can be represented in orbital notation with arrows indicating spin.
Electron configuration notation simplifies representation by using superscripts to indicate electron count.
The highest occupied energy level contains valence electrons, which are involved in chemical reactions.
Inner shell electrons are unreactive and are 'hidden' by the outer energy level's electrons.
The octet rule states that a complete outer energy level with eight electrons results in an unreactive atom.
Noble gases have full outer energy levels, making them unreactive and placing them on the far right of the periodic table.
Noble gas notation is a shorthand for electron configuration, using the noble gas's configuration plus additional electrons.
Electrons fill orbitals following the Aufbau principle, starting with the lowest energy and moving upwards.
The electron configuration for neon, a noble gas, is 1s2 2s2 2p6, representing a full outer shell.
For elements following neon in the periodic table, noble gas notation is used for electron configuration.
Transcripts
so today we're gonna be covering chapter
4 section 3 which is electron
configurations and the first thing you
need to know is that atoms and electrons
like most the rest of the universe like
to be in the lowest energy state
possible now what does that mean it
means that for electrons they like to be
in the ground state as close as possible
so as you can see this arrow indicates
increasing energy going down this way so
electrons tend to be in the lower
elements at least they occupy 1s first
than 2s 2p etc following these arrows
which indicate higher and higher energy
so there are some rules that govern how
electrons are configured in atoms and
the first is something called the Alpha
principle and what the Aufbau principle
basically says is that electrons will
first occupy the lowest energy possible
so they follow this rule right here and
you can see that again on the diagram
where they start here at the low energy
and then gradually increase following
these red arrows another thing you'll
notice is it tends to follow and a
pattern regards the number of the
orbital so it starts with 1 s and then
2s 2p 3s 3p etc but once you get up
above 1 & 2 it follows a strange thing
where the D or suborbital is actually
higher energy than the S sub orbital of
the next energy level so what ends up
happening is that electrons will fill up
for example the 4s orbital before they
fill up the e3d the next rule is
something called the Pauli exclusion
principle which is something you find in
both chemistry and physics and what the
poly exclusion principle says is that no
two electrons in the same atom can
have the same four quantum numbers and
basically what that means is that two
electrons that are in the same orbital
for example this one s orbital have to
have opposite spins because their other
three quantum numbers are the same so
let's say one has a spin of 1/2 that
means the other electron in that orbital
has to have a spin of negative 1/2 and
the last rule which we're covering today
which is hund's rule says that equal
energy orbitals must each be occupied by
one electron before they can be filled
by two and what this does is that minify
minimizes electron repulsion and ensures
that they have a lower energy because
there's not as much repulsion and so
basically what this means is if we
represent the spin numbers of negative
1/2 and 1/2 for electrons with arrows if
you're filling up an orbital let's say
this is a p orbital so that has three
subl rules of each let's say it's the 2p
over here it means that you have to fill
up each sub orbital with one electron so
if you were to go keep going you could
fill these three if you were to add
another electron you'd have to fill
these three before you could go back in
and then fill in this one with two
electrons and opposite spin States
because having these two electrons in
the same sub orbital while it is allowed
it's required that you do this state
first which has a lower energy because
these electrons will tend to repel each
other so how do we simplify this system
and represent these electron
configurations in like a better manner
well there's a few ways the first is
called orbital notation which is
probably the simplest way because it
involves drawing out every single
electron and in this case orbitals are
represented by lines like this and
electrons are represented simply by
arrows indicating their spin state
with the name of the orbital below it so
let's say this is the 1s orbital and if
we just put one electron in there that
would be hydrogen and then if you put a
second one in there
notice how I'm flipping the arrow around
to obey the Pauli exclusion principle
then this would become helium and then
we would do is go on to the next orbital
in the width in which case the next
lowest energy orbital is 2s and you'd
throw another electron in there and then
it would become lithium the second way
is something known as a simply electron
configuration notation and this is a lot
simpler because it just involves writing
and is more representative and basically
what you do is you use the name of the
orbital but with a superscript to
indicate the number of electrons in that
orbital let me demonstrate
so for example for hydrogen you would
write the orbital 1s 1 or 1 s rather and
then indicate the number of electrons in
this case just one helium you would do
I'm sorry 1 s and then 2 electrons and
for lithium the third element you would
fill up that orbital 1s 2 to obey the
outfile principle and then you would
move on to the next lowest orbital 2s
and then the number of electrons is just
1 again and just for some quick
terminology this 2s which is the highest
energy level in lithium which has an
electron in it is called the highest
occupied energy level and what that
means for the other electrons this is
also the electrons that are in this
energy level the two are also known as
valence electrons because they are the
ones that end up reacting during
chemical reactions and what that means
is these
1s2 electrons become what are known as
inner shell electrons which basically
means their unreactive they're sort of
hidden behind the energy level the shell
of the second orbital alright so here we
have what is somewhat close to a Bohr
model of the atom it's not quite
accurate but each orbital is represented
or sorry each energy level is
represented by color associations so or
energy level one is blue and energy
level two is red and then the sub
orbitals are represented by rings again
this is inaccurate the P orbitals are
actually sort of dumbbell shaped things
oriented around the new creel nucleus
differently but what this gives us is a
chance to see how you fill the orbitals
or at least the notation corresponding
to adding electrons so let's say you had
an atom of hydrogen so you just had one
electron here you just add the arrow
there or helium you'd again follow this
to obey the Pauli exclusion principle
and then if you moved on up to lithium
yet you're out of room in this lower
lowest energy level of 1s so you have to
move on up to obey the Aufbau principle
and then again you fill it up here and
again flipping the arrows to make sure
the spin states are opposite so that the
electrons can coexist and then here's
where it gets trickier if you want to
move on to boron let's say which is 1s2
2s2 2p1 you had the electron and then
let's skip a few let's go there's carbon
there's nitrogen there's oxygen alright
so then you had the arrow here here and
then you can come back and start filling
in like this
and you can continue with fluorine and
neon by filling in the rest of the
arrows and these all here in the second
energy level are valence electrons
because these are in the reactive outer
shell whereas these 1s1 are what are
called inner shell electrons and if you
wanted to write this all in electron
configuration notation you would put the
1s with two electrons 2's two electrons
and 2p with six electrons and that
corresponds to neon on the periodic
table now because neon has this full
outer shell or frontal outer energy
level rather it's the same thing with
different terminology of eight electrons
it follows something as which is called
the octet which basically means that
once it's filled completely this outer
energy level with eight electrons
it is now unreactive which is why it's
in a group called the noble gases which
you can see on the far right of your
periodic table and while this seems like
a lot of writing every time luckily
there is a shorthand known as noble gas
notation so for example if you wanted to
write the electron configuration
notation for sodium which has an
electron out here as well as the 1s2 2s2
2p6 you'd have to write out 1s2 2s2 2p6
3s1 and that would take forever if you
were to write it out for every element
so what you'll notice is that this part
is the exact same as neon so what you
can do is take the noble gas element
that precedes any element in the
periodic table obviously you can't do
this for hydrogen because it doesn't
have a noble gas that precedes it only
helium is the first one and that comes
after hydrogen but what you can do is
for every other element you can put that
in brackets as a substitute for all this
writing over here and then just add on
the additional part so the noble gas
notation for
sodium would be neon in parentheses with
the 3s1 on the end
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