# Electron Configurations The 2 nd address of the e -

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Electron Configurations The 2 nd address of the e -

Electron Configurations Electron configurations are a list of all the electrons in an atom (or ion). Electrons are attracted to a nucleus. They will move around the nucleus in predictable patterns. They will fill up available space inside the atom’s e- cloud. Electrons are attracted to a nucleus. They will move around the nucleus in predictable patterns. They will fill up available space inside the atom’s e- cloud. The Spaces allotted to electrons are inside the energy levels and are sub-energy levels or orbitals named s, p, d, & f. The Spaces allotted to electrons are inside the energy levels and are sub-energy levels or orbitals named s, p, d, & f.

S sub-energy sub-energy Number of Orbitals in Sub-energylevel Number of electrons in sub-energy level 1 35 2 610 7 14 How many electrons can be in a sublevel? A maximum of two electrons can be placed in any one orbital. p sub-energy sub-energyd f

How do electrons fill orbitals? fill orbitals?

Aufbau principle To Build up…. To Build up…. states that electrons fill from the lowest possible energy to the highest energy

Main energy level n=1 n=2 n=3 n=4 2 e - 8 e - 18 e - 32 e - 1s 2s 3s 4s 2p 3p 4p 3d 4d 4f 2 e - 6 e - 10 e - 14 e - ENERGYENERGY Max # of e- Sub-energy levele- per orbital

Electron Configurations 3p 2 Energy Level Sublevel Number of electrons in the sublevel 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 … etc.

Diagonal Rule s s 3p 3d s 2p s 4p 4d 4f s 5p 5d 5f 5g** s 6p 6d 6f** 6g** 6h** s 7p 7d** 7f** 7g** 7h** 7i** 1234567 Steps: 1.Write the energy levels top to bottom. 2.Write the orbitals in s, p, d, f order. Write the same number of orbitals as the energy level. 3.Draw diagonal lines from the top right to the bottom left. 4.To get the correct order, follow the arrows! **By this point, we are past the current periodic table so we can stop.

Let’s Try It! Write the electron configuration for the following elements: Write the electron configuration for the following elements: K, Zn, Pb K1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 Zn1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 Pb1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 2

Shorthand Notation We are only concerned about the outermost electrons. We are only concerned about the outermost electrons. We can use the noble gases as a method to represent all completely filled sub-energy levels. We can use the noble gases as a method to represent all completely filled sub-energy levels.

Shorthand Notation Step 1: It’s the Showcase Showdown! Step 1: It’s the Showcase Showdown! Find the closest noble gas to the atom, WITHOUT GOING OVER the number of electrons in the atom Write the noble gas in brackets [ ]. Step 2: Find where to resume by finding the next energy level. Step 2: Find where to resume by finding the next energy level. Step 3: Start with that energy level and use the __s 2 Resume the configuration until it’s finished. Step 3: Start with that energy level and use the __s 2 Resume the configuration until it’s finished.

Shorthand Notation Chlorine  Longhand is 1s 2 2s 2 2p 6 3s 2 3p 5 1s 2 2s 2 2p 6 3s 2 3p 5 You can abbreviate the first 10 electrons with the noble gas, Neon. [Ne] replaces 1s 2 2s 2 2p 6 3 is the next energy level after Ne So you start at level 3 with the diagonal rule start at level 3 with the diagonal rule (all levels start with s) Finish the configuration by adding 7 more e - to total 17 The Shorthand for Cl  [Ne] 3s 2 3p 5

Practice Shorthand Notation Write the shorthand notation for each of the following atoms: Write the shorthand notation for each of the following atoms: Ca, I, Bi Ca[Ar]4s 2 I[Kr]5s 2 4d 10 5p 5 Bi[Xe]6s 2 4f 14 5d 10 6p 3

Electron configuration of the elements of the first three series

e- configuration polka There’s a little game that’s as easy as can be, With numbers & letters & lots of chemistry. It comes from quantum theory & wave mechanic stuff, But for now just learn the game & that will be enough.

e - configuration polka Chorus 1s 2, 2s 2 then comes 2p 6, The e- configuration game is really slick. From the alkali to halogen and on to noble gas, Now you can understand the Periodic Law at last.

e- configuration polka Atoms have orbitals where e - like to play And those e - fill the orbitals in a special way. It’s a “building up” process-you can learn it in a second. And you can call it “Aufbau” if Deutsch is what you sprechen.

e - configuration polka Chorus 1s 2, 2s 2 then comes 2p 6, The e- configuration game is really slick. From the alkali to halogen and on to noble gas, Now you can understand the Periodic Law at last.

e- configuration polka The outermost e- in atoms have to be, The most important ones for understanding chemistry. These valence e- are shared, or lost or gained, In chemical reactions when atoms rearrange.

e - configuration polka Chorus 1s 2, 2s 2 then comes 2p 6, The e- configuration game is really slick. From the alkali to halogen and on to noble gas, Now you can understand the Periodic Law at last.

e - configuration polka But the joy is that now… in this point in history, But the joy is that now… in this point in history, We can finally solve the periodic table mystery. Why do elements form families, what is the explanation? Their valence e- have the same configuration.

e - configuration polka Chorus 1s 2, 2s 2 then comes 2p 6, The e- configuration game is really slick. From the alkali to halogen and on to noble gas, Now you can understand the Periodic Law at last.

Exceptions to the Aufbau Principle  Chemistry wouldn’t be any fun if it didn’t throw you a curve ball every now and then.  Some Atoms break the rules because they can exist in a configuration that maintains a lower energy.  There are many exceptions, but the most common ones are atoms that end with a d 4 and d 9 configuration.

Exceptions to the Aufbau Principle d 4 is one electron short of being HALF full ↑ ↑ ↑ ↑ __  In order to become more stable one of the closest s electrons will actually move over to the open d orbital. Ex.: Cr by rule would be [Ar] 4s 2 3d 4 The Exception makes it, [Ar] 4s 1 3d 5. The Exception makes it, [Ar] 4s 1 3d 5. Procedure: Find the closest s orbital. Steal 1 electron from it, and add it to the d. This will create a ½ filled lower energy, more stable configuration.

Exceptions to the Aufbau Principle OK, so this helps the d, but what about the poor s orbital that loses an electron? Remember, half full is good… and when an s loses 1, it too becomes half full! So… having the s half full and the d half full is usually a lower energy configuration than leaving the s full and the d sub-energy level with one empty orbital.

Exceptions to the Aufbau Principle d 9 is one electron short of being full ↑↓ ↑↓ ↑↓ ↑↓ ↑ _  Just like d 4, one of the closest s electrons will go into the d, this time making it d 10 instead of d 9. Ex: Au by rule would be [Xe] 6s 2 4f 14 5d 9, The exception makes it [Xe] 6s 1 4f 14 5d 10 Procedure: Same as before! Find the closest s orbital. Steal one electron from it, and add it to the d.

Irregular confirmations of Cr and Cu Chromium steals a 4s electron to half fill its 3d sublevel Copper steals a 4s electron to FILL its 3d sublevel

Try These Exceptions  Write the shorthand notation for: Cu, W Cu[Ar] 4s 1 3d 10 W[Xe] 6s 1 4f 14 5d 5

Electron Notations The 3 rd address of the e -

Orbital Diagrams Graphical representation of an electron configuration Graphical representation of an electron configuration Arrows are used to represent electrons. The direction and position of each arrow identifies the spin and which orbital within a sublevel an e- exists. sublevel an e- exists. Same rules apply  1. Aufbau principle 2. Pauli’s Exclusion principle 3. Hund’s Rule

Orbital Diagrams Hund’s Rule Hund’s Rule In orbitals of EQUAL ENERGY (p, d, and f), electrons will fill in each orbital before pairing up. In Monopoly, you have to build houses EVENLY. You can not put 2 houses on a property until all the properties in the set have at least 1 house.

LithiumLithium Group 1A Atomic number = 3 1s 2 2s 1 ---> 3 total electrons  . 1s 2s

CarbonCarbon Group 4A Atomic number = 6 1s 2 2s 2 2p 2 Here we see for the first time HUND’S RULE. When placing electrons in a set of orbitals having the same energy, we place them singly without pairing up.    . 1s 2s 2p

Draw these orbital diagrams! O, Cr, Hg O = [He]    . 2s 2p 2s 2p Cr = [Ar]       {Exception to Aufbau} 4s 3d 4s 3d Hg = [Xe]              6s 4f 5d 6s 4f 5d

Quantum Numbers The Final address of the e - The zip code of the electron!

Quantum Numbers Describe the location of electrons in an atom 1) n – principal (energy level) 2) l – azimuthal (energy sublevel) 3) m – magnetic (orbital) 4) s – spin (direction of electron spin) No two electrons in the same atom can have the same set of all four quantum numbers!

Assigning the Numbers  The three quantum numbers (n, l, and m) are integers.  The principal quantum number (n) cannot be zero. n must be 1, 2, 3, etc.  The angular momentum quantum number (l) can be any integer between 0 and n - 1. Ex. For n = 3, l can be either 0, 1, or 2.  The magnetic quantum number (m) can be any integer between -l and +l. Ex. For l = 2, m can be either -2, -1, 0, +1, or +2.

Quantum Numbers What are the quantum numbers of the last electron placed on Aluminum.

Quantum Numbers The Steps 1. Write out e- configurations for the element. 1. Write out e- configurations for the element. 2. Determine the e- notations for the element. Identify the last placed e- Example: Al  1s 2, 2s 2, 2p 6, 3s 2, 3p 1 Al  1s 2, 2s 2, 2p 6, 3s 2, 3p 1 Al  [Ne] ↑↓ ↑ _ __ __ 3s 3p Last placed electron

Quantum Numbers 3. Identify each quantum number for the last e- placed in the highest energy orbital. n  the energy level of the e- n = 1,2,3,..7 n  the energy level of the e- n = 1,2,3,..7 l  the sub-energy of the e- l = {s = 0, p=1, d=2, f=3} l  the sub-energy of the e- l = {s = 0, p=1, d=2, f=3} m  the specific orbital in which the e- is located. m  the specific orbital in which the e- is located. (Treat as a number line) m = 0 -1 0 +1 -2 -1 0 +1 +2 -3 -2 -1 0 +1 +2 +3 m = 0 -1 0 +1 -2 -1 0 +1 +2 -3 -2 -1 0 +1 +2 +3 s p d f s p d f s  The specific e- in the orbital. s = +½ for 1 st e- (up arrow) s  The specific e- in the orbital. s = +½ for 1 st e- (up arrow) s = -½ for 2 nd e- (down arrow) s = -½ for 2 nd e- (down arrow)

Quantum Numbers -1 0 +1 -1 0 +1 Ex.: Al  [Ne] ↑↓ ↑ _ __ __ 3s 3p 3s 3p Al  Last placed e- has the quantum #s Al  Last placed e- has the quantum #s n = 3, l = 1, m = -1, s = +½

Quantum Numbers Determine the Quantum # for these elements. Determine the Quantum # for these elements. Mg, Zn, and Kr Mg, Zn, and Kr Mg  [Ne] 3s 2    3, 0, 0, -½ Zn  [Ar] 4s 2, 3d 10         3,2,2, -½ Kr  [Ar] 4s 2, 3d 10, 4p 6            4, 1, 1,-½

Quantum Numbers Try to name these elements!! A) 3, 1, -1, -½ 3p 4  Sulfur B) 4, 1, 0, +½ 4p 2  Germanium c) 3, 2, -2, -½ 3d 6  Iron