Chapter 13: Orbitals and Electron Configurations Atomic Orbitals and Electron Configurations (Chap 13)

Quantum Mechanics (Heisenburg and Schrodinger) http://www Better than any previous model, quantum mechanics does explain how the atom behaves. Quantum mechanics treats electrons not as particles, but more as waves (like light waves) which can gain or lose energy. But they can’t gain or lose just any amount of energy. They gain or lose a “quantum” of energy. A quantum is just an amount of energy that the electron needs to gain (or lose) to move to the next energy level. In this case it is losing the energy and dropping a level.

Atomic Orbitals http://milesmathis.com/bohr2.jpg Much like the Bohr model, the energy levels in quantum mechanics describe locations where you are likely to find an electron. Orbitals are “geometric shapes” around the nucleus where electrons are found. Quantum mechanics calculates the probabilities where you are “likely” to find electrons.

Atomic Orbitals http://courses. chem. psu. edu/chem210/quantum/quantum Of course, you could find an electron anywhere if you looked hard enough. So scientists agreed to limit these calculations to locations where there was at least a 90% chance of finding an electron. Think of orbitals  as sort of a "border” for spaces around the nucleus inside which electrons are allowed. No more than 2 electrons can ever be in 1 orbital. The orbital just defines an “area” where you can find an electron.

Sub-levels = Specific Atomic Orbitals There are 4 types of atomic orbitals: s, p, d and f Each of these sub-levels represent the blocks on the periodic table. Blue = s block Yellow = p block Red = d block Green = f block

Energy Levels http://www.chem4kids.com/files/art/elem_pertable2.gif Quantum mechanics has a principal quantum number. It is represented by a little n. It represents the “energy level” similar to Bohr’s model. n=1 describes the first energy level n=2 describes the second energy level Etc. Each energy level represents a period or row on the periodic table. s sublevel begins at energy level 1 p sublevel begins at energy level 2 d sublevel begins at energy level 3 f sublevel begins at energy level 4

Orbitals http://media-2. web. britannica In the s block, electrons are going into s orbitals. In the p block, the s orbitals are full. New electrons are going into the p orbitals. In the d block, the s and p orbitals are full. New electrons are going into the d orbitals. What about the f block?

f-orbital = rosette VERY COMPLICATED SHAPE

Electron Configurations What do I mean by “electron configuration?” The electron configuration is the specific way in which the atomic orbitals are filled. Think of it as being similar to your address. The electron configuration tells me where all the electrons “live.”

No more than 2 Electrons in Any Orbital…ever. http://www. fnal The Pauli Exclusion Principle states that an atomic orbital may have up to 2 electrons and then it is full. The spins have to be opposite. We usually represent this with an up arrow and a down arrow. Wolfgang Pauli, yet another German Nobel Prize winner

Hund’s Rule http://intro. chem. okstate Hund’s Rule states that when you get to degenerate orbitals, you fill them all half way first, and then you start pairing up the electrons. Each orbital will get one electron before any gets two. Think of this rule as….. “SHARE BEFORE YOU PAIR” Don’t pair up the 2p electrons until all 3 orbitals are half full.

PRACTICE! NOW that we know the rules, we can try to write some electron configurations. Remember to use your orbital filling guide to determine WHICH orbital comes next. Lets write some electron configurations for the first few elements. Let’s start with hydrogen.

One last thing. Look at the previous slide and look at just hydrogen, lithium, sodium and potassium. Notice their electron configurations. Do you see any similarities? Since H and Li and Na and K are all in Group 1A, they all have a similar ending. (s1)

Electron Configurations Element Configuration H Z=1 1s1 Li Z=3 1s22s1 Na Z=11 1s22s22p63s1 K Z=19 1s22s22p63s23p64s1 This similar configuration causes them to behave the same chemically. It’s for that reason they are in the same family or group on the periodic table. Each group will have the same ending configuration, in this case something that ends in s1.

The End