Advanced Chemistry Unit 6 Quantum Mechanics

Advanced Chemistry Unit 6 Quantum Mechanics Things aren’t always as they seem…

Remember, Protons determine which element it is…. But Electrons determine what an element will do! In this unit, we will take a closer look at how electrons behave…..Quantum Mechanics

This is the model of the atom developed by Niels Bohr. It shows the electrons orbiting the nucleus in circular paths (1885-1962)

In the Bohr model, the valence electrons (the electrons involved in chemical bonding) are shown in the outer ring Sometimes we use this model to help us imagine how one atom can transfer an electron to another atom (ionic bonding)

In this model, the valence electrons (the electrons involved in chemical bonding) are shown in the outer ring Sometimes we use this model to help us imagine how one atom can share electrons with another atom (covalent bonding)

A more realistic model of where the electrons are in a Helium atom Bohr model of a helium atom The Bohr model works very well for many things, but it really doesn’t show the true complexity of the atom. In this chapter, we’re going to think about atoms, specifically their electrons, in a more complex way.

What do we know about electrons ? Electrons are moving around the nucleus at very high velocity – not necessarily in circular orbits Two hydrogen atoms combining to form one H2 molecule The electrons move so fast that - it would look like an electron cloud

Within the electron cloud, there are areas where you are more likely to find an electron and areas where finding an electron is less likely. Mathematicians call this “probability” An area where you are likely to find electrons is called an orbital. We will look at the different types of orbitals in a moment. But first, an analogy.

The boarding house analogy: A boarding house has many beds, in various floors and rooms. Each bed has its own designation, or address (the manager’s code)

The boarding house analogy – what’s the filling pattern?

What is the order in which the beds get filled? How does the manager keep track of which bed each guest is assigned to? We can think of electrons in a similar way. Electrons will have electron “address” that will tell us where in the atom are located.

s orbitals An s orbital can hold two electrons

p orbitals Each p orbital can hold two electrons There are three variations of bowtie shaped p orbitals (the difference between them is their orientation in space, like the x, y, and z axes on a graph)

d orbitals d orbitals really have interesting shapes…… “double dumbells” …and a “dumbell with a donut”! No, you don’t have to remember these shapes

f orbitals No, you don’t have to remember these shapes either

If an atom has several orbitals, you can see how they overlap, making the “electron cloud” have areas where it is more likely to find electrons

Ok, this is complicated… What do I really need to know about electron orbitals? Orbitals are areas where electrons are likely to be found Orbitals have different shapes (s=sphere, p=bowtie) The more electrons an atom has, the more places (orbitals) it will need to hold the electrons Showing where the electrons are located is like a game, and it is easy if you follow the rules….

Electron Orbital Notation Determine the number of electrons in the atom or ion Start with the 1s orbital and fill each orbital according to the guide (Aufbau principle) Show each electron as an arrow Add arrows (electrons) individually to the boxes until all electrons in the atom have been drawn Follow Hund’s rule and Pauli’s principle (more on this as we do the practice atoms)

Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p 3s 2p Each box can hold 2 electrons

Aufbau Principle- “building up” an electron occupies the lowest-energy orbital that can receive it This means start from the 1s and work your way upwards until you use all of electrons

Phosphorus 15 electrons For neutral atoms, the number of electrons is the same as the number of protons Let’s put them in the proper places on the orbital notation diagram

Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Phosphorus (15 electrons) The first two electrons go into the 1s orbital Notice the opposite arrow directions* 13 more electrons to go

Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Phosphorus The next electrons go into the 2s orbital 11 more to go

Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Phosphorus The next 6 electrons go into the 2p orbital One up arrow and one down arrow per box Fill separately before you double up in the same box only 5 more to go

Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Phosphorus The next 2 electrons go into the 3s orbital only 3 more to go

Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Phosphorus The last three electrons go into the 3p orbitals. They each go into separate boxes* They each show an “up” arrow*

Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Phosphorus The electron configuration for Phosphorus is 1s22s22p63s23p3

Why did we put one arrow up and one arrow down in each box? Pauli Exclusion Principle- just like no two houses can have the same address, no two electrons in the same atom can have the same “address”. If there are two electrons in the same orbital, we need to make one and the other (by tradition, we write the up arrow first)

When we filled the p orbitals, why did we put one arrow in each box before putting two in the same box? Hund’s Rule- orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second (fill each energy level separately before you double up)

The electron configuration for Phosphorus is 1s22s22p63s23p3

electron configuration! http://www.youtube.com/watch?v=Vb6kAxwSWgU

Electron Configuration ws Orbital Diagrams and Electron Configuration ws 1-12

Manganese 25 electrons For elements, the number of electrons is the same as the number of protons Let’s put them in the proper places on the orbital notation diagram

Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Manganese (25 electrons) The first two electrons go into the 1s orbital Notice the opposite arrow directions*

Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Manganese The next electrons go into the 2s orbital

Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Manganese The next 6 electrons go into the 2p orbital One up arrow and one down arrow per box

Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Manganese The next 2 electrons go into the 3s orbital

Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Manganese The next six electrons go into the 3p orbitals. That makes 18 electrons done…and 7 more to go

Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Manganese The next two go into the 4s orbital 20 electrons done….. 5 to go

Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Manganese The final five electrons go into the 3d level

Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Manganese The electron configuration for Manganese is 1s2 2s2 2p6 3s2 3p6 4s2 3d5

Let’s try some more Li Be B C N O F Ne This time we’ll save space and show the boxes as lines instead

Orbital notation (arrows) Element Electron Configuration Orbital notation (arrows) Lithium (3e-) 1s22s1 ____ ____ ____ ____ ____ 1s 2s 2p Beryllium (4e-) 1s22s2 Boron (5e-) 1s22s2p1 Carbon (6e-) 1s22s2p2 Nitrogen (7e-) 1s22s2p3 1s 2s 2p Oxygen (8e-) 1s22s2p4 Fluorine (9e-) 1s22s2p5 Neon (10e-) 1s22s2p6

Valence electrons- the electrons involved in chemical bonding….. …how are these determined?

Valence electrons are the electrons in the outermost energy level These are the electrons that determine if/how an atom will bond with other atoms 1s 2s 2p 3s 3p Silicon has 4 valence electrons

How many valence electrons does Chlorine have? 1s 2s 2p 3s 3p

Can you locate the valence electrons in this atom of Cobalt ? Valence electrons are the electrons in the outermost energy level These are the electrons that determine if/how an atom will bond with other atoms

Valence Electrons How many valence electrons does Bromine have?

How many valence electrons does a Bromine ion have?

Orbital notation (arrows) Element Electron Configuration Orbital notation (arrows) Lithium (3e-) 1s22s1 ____ ____ ____ ____ ____ 1s 2s 2p Beryllium (4e-) 1s22s2 Boron (5e-) 1s22s2p1 Carbon (6e-) 1s22s2p2 Nitrogen (7e-) 1s22s2p3 1s 2s 2p Oxygen (8e-) 1s22s2p4 Fluorine (9e-) 1s22s2p5 Neon (10e-) 1s22s2p6 How many valence electrons does each atom have?

Is there an overall pattern? What are the electron configuration patterns for different families of elements? Is there an overall pattern? Chalcogens

Electron Configuration for Alkali Metals Electron configuration end in s1 Outer level has 1 valence electron 1s2 2s2 2p6 3s1 Example: Sodium 1s 2s 2p 3s

Electron Configuration for Alkaline Earth Metals Electron configuration ends in s2 2 valence electrons 1s2 2s2 2p6 3s2 3p6 4s2 1s 2s 2p 3s 3p 4s

Electron Configuration for Halogens Electron configuration ends in p5 7 valence electrons 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5 Example: Bromine 1s 2s 2p 3s 3p 1s 2s 2p 3s 3p 4s 3d 4p 4s 3d 4p

Electron Configuration for Noble Gases Except for Helium, they all end in p6 Helium ends in s2 (it only has 2 electrons) Atoms are especially stable when the s and p sublevels are full (8 valence electrons) Example: Argon 1s 2s 2p 3s 3p 1s2 2s2 2p6 3s2 3p6 Outer level (3rd level) has a total of 8 electrons

Electron Configuration ws Orbital Diagrams and Electron Configuration ws 13-40

Even if you don’t have the electron filling cheat sheet, there are two other ways to figure out the electron configuration: Create your own cheat sheet Use the layout of the periodic table

Create your own cheat sheet … (1-7 spdf) 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f

Create your own cheat sheet … Then fill from the bottom up following the arrows 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f 1s2 = 2 electrons

Create your own cheat sheet … Then fill from the bottom up following the arrows 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f 1s2 2s2 = 4 electrons

Create your own cheat sheet … Then fill from the bottom up following the arrows 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f 1s2 2s2 2p6 3s2 = 12 electrons

Create your own cheat sheet … Then fill from the bottom up following the arrows 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f 1s2 2s2 2p6 3s2 3p6 4s2 = 20 electrons

Create your own cheat sheet … Then fill from the bottom up following the arrows 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 = 38 electrons Notice how the 4th level begins filling before the 3rd is finished filling

Create your own cheat sheet … Then fill from the bottom up following the arrows 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 = 56 electrons

Use the periodic table layout

Use the periodic table layout

More Practice: # e- Configuration Na 11 1s22s22p63s1 Cl 17 1s22s22p63s23p5 Sb 51 1s22s22p63s23p64s23d104p65s24d105p3 K 19 1s22s22p63s23p64s1

Noble Gas “Shortcut” The shape of the periodic table is a helpful clue When we get to the end of the period, the outermost energy level is full (noble gas) Write the symbol of the noble gas that comes before the element we are looking for [in brackets] Then write the rest of the electrons Magnesium is 1s22s22p63s2 But Neon is 1s22s22p6 Shortcut for Magnesium: [Ne]3s2

Noble Gas “Shortcut” Example 3 Write the symbol of the noble gas that comes before the element we are looking for Then write the rest of the electrons Chlorine is 1s22s22p63s23p5 Neon is 1s22s22p6 Shortcut for Chlorine: [Ne]3s23p5

Noble Gas “Shortcut” Example 4 Write the symbol of the noble gas that comes before the element we are looking for Then write the rest of the electrons Potassium is 1s22s22p63s23p64s1 Argon is 1s22s22p63s23p6 Shortcut for Potassium: [Ar]4s1

A noble gas cannot be its own shortcut! Noble Gas “Shortcut” Example 5 Write the symbol of the noble gas that comes before the element we are looking for Then write the rest of the electrons Ex: Argon: 1s22s22p63s23p6 Argon is 1s22s22p63s23p6 Shortcut for Argon: [Ar] NO! A noble gas cannot be its own shortcut!

Figure out the shortcut for 51Sb 1s22s22p63s23p64s23d104p65s24d105p3 1s22s22p63s23p64s23d104p6 Kr So, the shortcut is: [Kr] 5s24d105p3

Go backward until you hit a noble gas Figure out the shortcut for 51Sb using the table Kr Go backward until you hit a noble gas

Figure out the shortcut for 51Sb using the table 5p3 5s2 4d10 [Kr]

[Kr] 5s24d105p3 Figure out the shortcut for 51Sb using the table So, the shortcut for Sb is: [Kr] 5s24d105p3

Write the complete electron configuration and the noble gas shortcut electron configuration for Polonium (Po) Xenon (Xe)

Electron Configuration ws Orbital Diagrams and Electron Configuration ws