Orbital Diagrams & Electron Configuration: Step-by-Step Guide

hello everyone and welcome back my name is mr cobalt and in this video i'm going to go over

orbital diagrams and electron configuration so in a previous video i talked about uh

the different uh strategies or different principles and rules that you need to follow in order to fill in the table so

i'm going to use those principles and that rule to fill in some examples and then i'm

going to show you how you can write electron configurations and what the electron configuration is

okay so let's get into this so if you remember there was the aufbau

principle and the aufbau principle said that electrons want to be in the lowest

energy possible so they're going to start low and then they're going to work our way

up so when we're putting our electrons into the orbital diagram we're going to start low

and one of the things i want to say off the off the bat is we want to think of the orbital diagram

as kind of a hotel if you will and each orbital is a room in the hotel

so we can break this down so let's say this is our hotel and

our hotel has various rooms and so there are different

floors to the hotel so think of the energy level as the floor

of your hotel so we have energy level number one we have energy level number two

energy level number three and so on so these would be floors of the hotel

and then we have what they're called the sub levels the p the s

the d and the f so we have these sub levels that are broken down into orbitals and each sub-level has a

certain amount of orbitals in it right so you can think of the sub-level

as kind of a suite right so there are different suites on the

floor of your hotel there are suites that have one room there are suites that have

two rooms or three rooms or four rooms so depending on how big the suite is right so you can think of

different sub levels as being the suites of the floor

and so in the suite you have rooms and you can think of the

orbitals in the suite as the rooms right so here we have

the d suite and in the d suite there are five rooms that you can occupy

and so there's a maximum of two people per room right so let's say imagine there's two beds

in each room so you can

you can house or have two as as the maximum of only two roommates possible

so if we kind of follow that that analogy then we can think of the

electrons as people going into the hotel and choosing their rooms right and it's like first come

first serve and electrons don't want to go into the higher levels because in this hotel there is no elevator there's

only the stairs so who wants to take the stairs so when you're putting electrons into the

orbital diagram think of it as people or guests coming to the hotel and they're going to want to fill in the bottom

first right so as we're

putting electrons into their locations different rooms of the hotel this is

uh how the electrons are structured in the atom so the question is where are all these electrons so you have uh some

atoms have 84 electrons well where are they all well this is the answer to the question

this is where they are right so some electrons are down in the energy level number one

some electrons are in energy levels number four uh

some are in the s sub level some are in the p somewhere in the d so where are they

so the answer to this question is the

orbital diagram so the number of electrons of the atom is going to be important how we fill them in is going

to be important to figure out where they are at and so that's the reason for the aufbau principle the pauli exclusion

principle and hund's rule so it's it's those are to help us figure out where the electrons are

okay so with that in mind let's go over some examples so i'm going to pick uh some examples on the periodic table so

let's let's go ahead and pick um

chlorine so chlorine is number 17 on the periodic table so here

uh chlorine so number 17 it has

uh 17 electrons because it's number 17 it has 17 protons that's the atomic number we're assuming the atom is

neutral and so we are going to put in 17 electrons and so the alpha rule says that electrons want to be the lowest

energy possible so when we're putting electrons into our hotel if you will

uh we're gonna start with the low energy and work our way up until we've put all of our electrons into the orbital

diagram our hotel right so we're going to start here

so this is the sub level so this sublevel s the s sublevel only has one orbital so each line represents an

orbital or a room so the first floor of your hotel only has one suite and that's one sweep only has one room so we're

going to put two people into that room and they've got to be

spin up spin down you could think of this as they have to be male and female in order to occupy a room that's just

the rule it can't be two males can't be two females got to be male and female so that's kind of a fitting the analogy

there um so so we take our 17 electrons and we start filling in our hotel so we start

with the bottom and work our way up so spin up spin down so that

that level is now full so this

um this floor is full it only has one suite only has one room so now whoever wants

to go in is going to need to go to the next floor so now we're going to fill in the next four

so the sweet 2s gets filled up so here we're going to put

two of our electrons spin up spin down that suite is full with its one room now we go to the next suite the p suite

the two p sweep on the second floor right two means second floor second energy level

uh so notice there's three rooms three orbitals remember that's the px pypz

and so we're gonna put electrons into there but remember hund's rule says that you need them if you have equal

orbital orbitals of equal energy you're going to fill in one electron at a time and they have to have

the same spin so here we're going to fill in one two

three so this is like three people wanting to have a single room by themselves first

so if this electron goes into this room this electron is not going to bunk bed or share a room so they want their own

room so they're going to go to this one and the third one goes this one but then if you have more electrons then there's

no choice you're gonna have to you're gonna have to be roommates with someone okay

so then here we have one two three four five six seven we have ten more electrons so we

got to keep filling so sorry we gotta put two together so spin out spin down

spin up spin down spin up spin down so now we have 10 electrons we need

seven more so we keep going so the next one is the 3x so we keep going up in energy 3s

so we put two electrons in there spin up spin down so there's two now we gotta go in next

level and we gotta follow hund's row remember the fact that we have to have spin up

spin down in one orbital is the poly exclusion principle so remember the poly exclusion principle says that we can

only have a maximum of two electrons in an orbital and they have to be opposite spins

okay so here we have three p so we're gonna have to fill that in with electrons so

again following hund's rule we put them up one at a time we get our room by ourselves

first spin up spin out spin up so they're all the same spin

that's three right so right now we have one two three four five six seven eight nine 10 11 12

13 14 15. so we have 17 electrons two more to put in so now we have to do spin down

and spin down so that's 17 electrons so this is the electron structure of

chlorine this is where the electrons are at in the atom these are the sublevels these are the orbitals that the

electrons are occupying in the atom chlorine and so

this is what the orbital diagram shows us and so one of the things i want to point

out is you'll notice that the chlorine

has almost a full

third shell here so we have 3s and you have this electron here that doesn't have a pair now that's

electron wants to be paired um because that nut would complete this kind of level here the 3s so that

makes chlorine quite reactive it wants to get an electron so it can complete that

outer shell okay so what can i do with this there's a

shorthand way that i can represent and write this out to represent how the electrons are housed in my orbital

diagram in my hotel if you will so how can i represent this where can i say

the electrons are well all i do is i start from the bottom

and i work my way up following offball principle and i write down the number of the energy level

the letter for the sub level and then i write uh i write a

superscript for the number of electrons at that level so what do i mean so let's do this

so notice i have two electrons in the 1s so what do i do

i write 1 s so that's the first

sublevel i write that and how many electrons do i have i have two so i put a superscript two so 1s2 so that means i

have two electrons in this 1s sublevel now

i go to the 2s so next i write 2x how many electrons do i have in a 2s 2

so i put a superscript 2 for the number of electrons i have at that sub level and all i'm doing is i'm going up as i

go up in energy i'm following the energy and i'm increasing energy i'm going from low to high and as i'm going through the

floors through the different levels i'm writing down the number

the ladder and the number of electrons in that sublevel so here 2s what follows the 2s

the 2p and how many electrons do i have that's 6. so i'm going to write 2p

6. so superscript 6 tells me those are the six electrons that go into these three

orbitals at this level okay next is going up to the next higher higher level that's 3s so i'm going to

write 3s and then how many electrons do i have 2 so i'm going to put

superscript 2. and then i go to the next one so the next one is 3p

and so i write 3p and how many electrons do i have in here 1 2 3 4 5.

so there there it is so

the order of the electrons in my chlorine atom is written out according to from according

from lowest energy to highest energy and all i do is i write it out this way

in the same order writing down the number of electrons that i have in each sublevel going from

lowest energy to highest energy and that's it and this ladies and gentlemen

is referred to as electron configuration

sorry about that lights so this is the electron configuration so the electron configuration of

chlorine comes directly from how you put the electrons in the orbital diagram so if the electrons are are

structured in this way then you write it this way and this is the electron configuration

of the atom of chlorine let's go ahead and do another example

so instead of chlorine let's do another one let's do silver

silver is number 47. so we got 47 electrons so here we have

excuse me here we have uh 17 so now we have to add 30 more electrons

so we're going to go to 47. so we keep adding so we put spin

down here that's 18 so we have 3p so let me put silver here oops

we're going to put silver all right so i again i start from the bottom up and i continue

so here i have 18 3p and then after the 3p the next is 4s so

this is 18 spin up spin down that's 20 and then i go to

3d is next i'm not going to 4p because 3d is lower in energy so we're going to go to this one because again we want

electrons want to be in the lowest energy possible so as our guests to the hotel are coming in they want the lowest

floors possible they don't want to go up any more stairs than they have to so this

after the 4s is the 3d and so hund's roll we're going to do spin up

spin up spin up spin up

spin up and then we keep going spin down

spin down spin down spin down spin down so that's 10

so this was 20 this is 30. so we have 47 electrons so we got 17 more to go so this is 30

next is p4 so next in energy is p4 so hun's rule again spin up

spin up spin up they want the rooms by themselves

and then we keep adding and now we pair them up so that's six

so now we have 36 so keep going we got 11 more

so after the 4p what's next the next energy is the 5s so we're going to add

to that spin up spin down so we're going to put electrons into that room and so now

we have 38 so we want 47

so let me double check so we have 2 4 10 18 20

30 36 38

and now we want to put in 47 and so the next one over is going to be the 4d

so we got 40 we got

38 so this is going to be 36

37 38 39

40 and then 41 42

[Music] 43 uh

40 hello uh i miscounted 2 4

10 18 20 30 36 38

39 40 41 for two for three foot four 45 46 47 there we go i had i needed one more

all right so here we have 47 and so this here is where the electrons are in the atom of silver

so now if we write our electronic configuration all we need to do is copy

everything from the bottom following the order of increasing energy levels and we write it in the

order so again we start at 1s so the electron configuration is going to be 1s

2 because we have 2 electrons here next 2s 2 electrons so 2s2

next 2p six electrons so that's going to be 2p6

next 3s 2 electrons 3s2

next 3p 6 electrons so that's going to be

3 p6 next

4s 2 electrons four s two

okay we gotta keep going so next is going to be three d that's gonna be

three d and we have ten electrons so that's going to be 3d 10.

next is 4p they have 6 electrons so 4 p6 next is 5s with two electrons

five s two oops that's an ugly two five s two and then next is

four d nine so we're gonna put four d so we're in 4d and there's 9 electrons

so we put superscript 9. so this this is where the electrons are located

in silver so if you count the subscripts 2 4

10 12 18 and you count you'll get 47 you'll

count 47 and this tells you where the electrons are in silver

we have two in the 1s sublevel we have 2 and the 2x we have 6 in the 3 orbitals in the 2p and so on

so this tells you what the structure of the electrons are in

in the atom so i hope this was helpful i hope these examples clarified everything if you like this video please hit that

like button subscribe to my channel hit that notification bell if you want to get

more videos that i post out on a regular basis please put a comment in the comment section let me

know what you think and ask me questions thanks for joining me have a great day