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Chemistry library
Course: Chemistry library > Unit 7
Lesson 4: Electron configurations- Shells, subshells, and orbitals
- Introduction to electron configurations
- Noble gas configuration
- Electron configurations for the first period
- Electron configurations for the second period
- Electron configurations for the third and fourth periods
- Electron configurations of the 3d transition metals
- Electron configurations
- Paramagnetism and diamagnetism
- The Aufbau principle
- Valence electrons
- Valence electrons and ionic compounds
- Valence electrons and ionic compounds
- Atomic structure and electron configuration
- Introduction to photoelectron spectroscopy
- Photoelectron spectroscopy
- Photoelectron spectroscopy
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Noble gas configuration
How to write electron configurations for atoms and monatomic ions using noble gas configuration.
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- Why do shells name by letters S, P, D, F?(40 votes)
- Great question and good trivia for any Chemistry enthusiasts:
The line groups (subshells) were called sharp, principal, diffuse, and fundamental. When the angular momentum quantum number was used to describe and explain these groups of lines, s became an abbreviation for = 0, p meant = 1, d meant = 2, and f meant = 3.
Luckily, this is now meaningless, so don't worry what they really mean :-)(92 votes)
- What would the noble gas electron configuration for an element look like if the element is a noble gas? Would it be
[Ar]
or[Ne]3s^23p^6
?(16 votes)- It depends on what your instructor wants.
Personally, I would choose [Ar].(7 votes)
- What does it mean "Full Octet" ?(4 votes)
- "Full octet" means that there are eight electrons in the outer electron shell of an atom.(15 votes)
- Please help, I did not understand what happened after we wrote Neon at. Why did we write 3s^2 and 3p^2. 3:20(5 votes)
- What she was doing was writing the electron configuration of silicon. Written in full this is 1s2 2s2 2s6 3s2 3p2. However, the first part of this long expression, 1s2 2s2 2s6, is the electron configuration of neon. Therefore, to shorten the configuration for silicon she wrote [Ne] 3s2 3p2.
All that this means is that silicon has a core structure that is the same as neon, but then has four more electrons (3s2 3p2). It's just a short cut and it is commonly used. Furthermore, it is helpful because the outer electrons (3s2 3p2) are the valence electrons and these are the ones that are of most importance.(10 votes)
- For Calcium, why is the electron configuration not contain "d", for the 3rd subshell section, before writing 4s2?(6 votes)
- For potassium and calcium, the 4s orbital is at a lower energy than the 3d orbitals.(4 votes)
- So the first shell consists of s orbitals, second shell s and p orbitals , third shell s,p and d orbitals and fourth shell s,pd,and f orbitals, what about the other shells like the fifth shell and beyond, does it remains as s p d and f orbitals only or it extends to g h and so on ? Also correct me if I am wrong about the shell part,thanks in advance !(4 votes)
- It does extend to g, h, i, and so on. However, there are no elements currently known which use anything beyond f orbitals in their ground state electron configuration.(6 votes)
- How can we tell what shell can fit what number of electrons? From the examples i figured- the 's' shells can take a maximum of 2 electrons and 'p' shells can take a maximum of 6 electrons. Is this right?(3 votes)
- See the 4 subshells we know till now are S,P,D,F and each has value given below
S=2 , P=6 , D=10 , AND F=14 . these numbers are no. of electrons the respective sub shells can hold .(4 votes)
- Can someone please remind me why she has written another s after the p atand then another p. 2:53
Also, why does she have a 6 at the top of the first p at? 2:53
Why not a 2?(3 votes)- Pay attention to the numbers in front of the letters, they’re important. It’s not just s and p, it’s 1s then 2s then 2p then 3s etc.
p orbitals can hold 6 electrons, s orbitals can hold 2 electrons(4 votes)
- what exactly are valence electrons?(2 votes)
- They are the electrons that take part in bonding and chemical reactions(4 votes)
- So why does calcium prefer to lose 2 electrons? Why can't silicon gain or lose 4 valence electrons?(3 votes)
- Because Ca has 2 electrons in its outermost shell and it’s much easier to lose 2 than gain 6.
Silicon could...but we find it forms covalent bonds instead, it shares electrons with other elements to fill its outermost shell. Nonmetals generally behave like this rather than forming ions.(3 votes)
Video transcript
- [Voiceover] In this video,
we're going to be talking about how you can write electron configurations using noble gas notation. And to be more specific, in this video we're also
going to be focusing on examples using main group elements. So, we're doing that because
the transition metals, right here, and the lanthanides, are a little bit more complicated, so we won't be doing that
in this particular video. So the rule for writing the noble gas notation for something is pretty simple. It is, you take the noble gas immediately preceding your atom or ion, so what do I mean by
immediately preceding? That means we want the
noble gas that comes right before it, so you go up a row, and you go over to here, where the noble gases live. And you put that in brackets
and then you write your other electrons, and you write
your other electrons using the same notation
that you normally write electron configurations in. If you don't remember what that is, we'll go through a couple
examples right now. So hopefully it will become more clear. So before we get started, I'm just going to remind you
why we call the noble gases noble, and that is because they have a full octet of electrons. And so, since they have a
full octet, they're not very reactive, they have all of the electrons they want, and as a result, you will see in chemistry
that a lot of chemistry, chemical reactions will be driven by other non-noble gases trying
to get a full octet. So the first example
we're going to talk about and write the configuration
for is silicon. Silicon is right below
carbon in the Periodic Table, and we can write its full
electron configuration, just for comparison, so if we start up here, with hydrogen, silicon has
the electron configuration 1s2 2s2 2p6, so as a reminder, these
are our S electrons because they're in S orbitals. These are our P electrons because they're in P orbitals, and then once we're through our 2p6 electrons, we go to 3s2 and we have two more electrons, so it's 3p2. So that's the electron
configuration for silicon. Now, we can write it out
using noble gas notation. And compare, so, the noble gas immediately
preceding silicon, if we go up a row and then move over, we see that it's neon. So we write neon in brackets. And then, the other electrons are the ones that come after neon. So we go down, and the electrons that
aren't included in neon would be our 3s2 electrons, right here, and the 3p2 electrons. So if we compare these two ways of writing our electron configuration, you can see that these electrons right here, so everything up to 3s2 3p2, that gives us the electron
configuration for neon. And so we don't have to write that, we just write neon, and assume that whoever's reading it knows what the electron
configuration for neon is. The other thing you might notice is that these other electrons here, that we wrote outside of the brackets, these are our valence electrons. So, writing your electron configuration this way, using noble gas notation, makes it really obvious where
your valence electrons are and what kind they are, so that's helpful. We are going to go
through one more example and that will be calcium. So calcium is over here, and so, we're not going
to write the full electron configuration this time. We're just going to write
the noble gas notation. So calcium, the noble gas
immediately preceding it, we go up a row and then
over and we see that the noble gas is argon, so we write argon in our brackets, and then, what electrons are not in argon? So we move down and we
see that we have our 4s electrons, and we have two of them. So this is the noble gas
configuration for calcium. So does calcium have a full octet? And we know that these
are the valence electrons and we also know that if
it did have a full octet, it would actually already have
a noble gas configuration, so it would either have krypton or argon and in this case, it
turns out that calcium prefers to lose two electrons, as opposed to gaining a bunch. It would be gaining 10 plus six. So, lose two electrons,
and when calcium loses two electrons, it becomes the
calcium 2-plus cation. And then we can write the electron configuration really short, or it'll be really short because we know it's going
to lose these two valence electrons and then, it will have the electron
configuration which is just the same as argon. And we can tell, really
easily, looking at this, that calcium 2-plus has a full octet. So, one of the many pros of writing things
in noble gas notation, besides the fact that it, you know, makes your hand less tired, is that it makes it
really easy to see where your valence electrons are, and whether or not your ion
or atom has a full octet.