3 Neils Bohr model of the Atom: Electrons can be in 1 of many “principle energy levels”, but cannot be in betweenany of these energy levels.Each Principle Energy Level (n) is given a numbern=1n=2n=3Electrons move around the nucleus like planets move around the sun.
4 Unfortunately, Bohr’s model of the Hydrogen atom turned out to be incorrect, so a new model was introduced.But, This!Not This!
5 What are the Quantum Numbers? Remember – they give the approximate location of electrons in an atom.They are actually represented by letters.N – distance (size of orbital)l – Shape of orbitalm – orientation in space of orbitals – spin of the electron
6 Erwin Schrödinger, using complex mathematics, calculated the probability of where an electron is located.The probability of an electron in the first principle energy level:An orbital is drawn that encloses the region where the electron is found 90% of the time.
7 First Energy Level (n=1) can contain 1 sublevel orbital Second Energy Level (n=2) can contain 2 sublevel orbitalsThird Energy Level (n=3) can contain 3 sublevel orbitals and so on…There are many types of sublevels:
8 ShapeNameMaximum # of electronsLowestEnergys2Sphericalp6HighestEnergyDumbellDumbell
9 Maximum # of electronsNameShapeLowestEnergyd10fHighestEnergy14f
10 The next sublevel is g. How many electrons would it hold? What type of sublevel orbital(s) would be found in the first principle energy level (n=1)? How many electrons will it hold?What type of sublevel orbital(s) would be found in the second principle energy level (n=2)? How many electrons will it hold?What type of sublevel orbital(s) would be found in the third principle energy level (n=3)? How many electrons will it hold?
12 Called the Pauli exclusion principle Each sublevel orbital can hold 2 electrons, which have opposite magnetic fields. Therefore, we say that each electron has a spin, which is opposite of each other. This is symbolized by:Called the Pauli exclusion principle
14 Electron Configurations Using quantum numbers to give the arrangement of electrons around the nucleus.There are three rules that must be followed!
15 Rule #1 AUFBAU principle Electrons fill low energy orbitals first s,p,d then fFilling order1s2s2p3s3p4s3d4p5s4d5p6s4f5d6p7s5f6d7p
16 Rule #2 Pauli Exclusion Principle Since there are two possible spins for an electron, no more than two electrons may fill an orbital.Remember: s = 1 orbital, p = 3 orbitals, d = 5 orbitals and f = 7 orbitals
17 Rule # 3Hund’s RuleWhen multiple shapes are present, electrons fill orbitals with parallel spins before pairing up.Must follow rule #2!Example 2p
18 Write the following electron configurations LiNaBeCSi
19 Using the Periodic Table Read from left to right and top to bottom.Stop when you:Reach the end of a rowChange colorReach the element of interestTry the following Mg, B, Ne and Cl
20 Short-CutSkip back to the previous Noble Gas (core electrons) and start with the element after that.Try: I, U, Fe