2. The Quantum Model of the Atom Mrs. Johnson

3. de Broglie Light behaves as both a wave and a particle So do eˉ ( they are particles, but also have wave like properties because they can be bent, or diffracted)

4. Bohr vs. the Quantum Model In each energy level, a certain amount of electrons can fit 2n 2 When n=1, there are 2 electrons When n=2, there are 8 electrons When n=3, there are 18 electrons When n=4, there are 32 electrons

5. Electrons do not travel around the nucleus in neat orbits, said by Bohr They exist in certain regions called orbitals Orbital-3 dimensional region around the nucleus that indicates the probable location of an eˉ Energy of eˉ are higher when further from nucleus Electrons

6. Uncertainty Principle Can confine an eˉ to a specific energy level (quanta) or region of an atom It mathematically isolates an eˉ to a specific orbital, but cannot tell its exact position Schrodinger’s equation allows physicists to find the probable location of an eˉ

7. Quantum Numbers Specify the properties of atomic orbitals and the properties of e‾ in orbitals 1 st three quantum #’s: indicate the main energy level, the shape and the orientation of an orbital 4 th #: spin #- describes a fundamental state of the eˉ that occupies the orbital

8. Principle Quantum #-n Indicates the main energy level occupied by the eˉ n-positive integers- 1,2,3… As n increases, the eˉ’s energy and its av. distance from the nucleus increases n=1, occupies the 1 st or lowest main energy level and is located closest to the nucleus

9. n More than one eˉ can have the same n value These eˉ’s are sometimes said to be in the same eˉ shell or main energy level When n=1, 2 e can fit When n=2, 8 e can fit How many e will fit when n=3 and n=4? Answers: 18, 32

10. On your own What is the value of n for electron in H? What is the value of n for the last e in Cl? What is the value of n for the last e in Cu? Answers: n=1, n=3, n=4

11. Angular Momentum Quantum #- l Indicates shape of orbital Sublevels: orbitals of different shapes Sublevels exist for a given value of n except for the 1 st main energy level The # of orbital shapes possible=n l = 0 and all possible integers less than or equal to n-1

12. Examples When n=2 How many shapes are there? Answer: 2 What is l equal to? n-1 or (2-1) So l = 1 and l =0

13. Orbital Letter Designations for values of l 0 s 1 p 2 d 3 f

14. Sublevels s-spherical p-have dumbbell shapes d-more complex f- too complex

15. Try This When n=1, how many orbitals does it have, what is the value for l and which sublevel is it in? When n=2? When n=3? When n=4?

16. Answers When n=1, there is only 1 orbital, l=0 and it is only in the s sublevel When n=2, there are 2 possible orbitals, l=0 and 1, and it is in the s and p sublevels When n=3, there are 3 possible orbitals, l=0, 1 and 2, and it is in s, p,and d sublevels When n=4, there are 4 possible orbitals, l=0,1,2 and 3, s,p,d,f sublevels

17. Magnetic Quantum #-m l Indicates the # of orbitals per sublevel(orientations) Atomic orbitals can have the same shape, but different orientations around the nucleus When l=0, m=0 When l=1, m=-1,m=0,m=1(3 orientations) When l=2, m=-2,m=-1,m=0,m=1,m=2 (5 orientations)

18. Spin Quantum # m s An e in an orbital can be thought of as spinning on an internal axis It spins in 1 of 2 possible directions or states As it spins, it creates a negative field 2 possible values +1/2 and –1/2 A single orientation can hold a maximum of 2 e which must have opposite signs

19. Electron Configuration The arrangement of e in an atom Each atom of each element has its own e arrange themselves so that they have the lowest possible energies The lowest–energy arrangement of the e’s is called the element’s ground-state config. There are rules that allow us to determine these ground-state configurations

20. Aufbau Principle-1 st Rule Shows the order in which e’s occupy orbitals An e occupies the lowest-energy orbital that can receive it Figure 11.32 (atomic orbitals in order of increasing energy) Which orbital has the lowest energy? What about the next lowest energy?

21. Aufbau con’t What looks strange about the order as energy increases? Beginning with n=3, the energies of the sublevels in different main energy levels begin to overlap The 4s sublevel is lower in energy than the 3d sublevel, so the 4s orbital is filled before any e’s enter the 3d orbitals

22. Why? Less energy is required for 2 e’s to pair up in the 4s orbital than for a single e to occupy a 3d orbital What sublevel is filled next after 3d? Pauli Exclusion Principle-no two e’s in the same atom can have the same set of quantum #’s ( 3 are the same)

23. Pauli Exclusion Principle 2 e’s can occupy the same orbital, but must have opposite spins Each arrow represents 1 of the atoms 2 e’s The direction of the arrow represents the e’s spin

24. Hund’s Rule Orbitals of equal energy are each occupied by 1 e before any orbital is occupied by a 2 nd e All e’s in singly occupied orbitals must have the same spin e-e repulsion is minimized so e arrangements can have the lowest energy possible What is the max # of unpaired e’s in a d sublevel?

25. Representing e configurations 3 notations 1)orbital notation 2)e configuration notation 3)noble-gas notation Orbital Notation _____=unoccupied orbital Orbital’s name is written below the line n&l