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# The Quantum Mechanical Model & Electron Configurations

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1. The Quantum Mechanical Model & Electron Configurations

2. Quantum Mechanical Model • Has energy levels for electrons. • Orbits are not circular (clouds). • It can only tell us the probability of finding an electron a certain distance from the nucleus.

3. The Quantum Mechanical Model • Heisenberg Uncertainty Principle---it is impossible to know both the exact position and momentum of an object at the same time. • Can’t know position if e- is moving. • Can’t know momentum if e- is not moving.

4. Where are the electrons found? Think Apartment Building: • Nucleus is the Ground Floor • Energy Levels are floors, n = 1, 2, 3,… • Each floor, or Energy level above the Nucleus has different types of Apartments or Sub orbitals

5. Electron Energy Level (Shell) • Generally symbolized by n, it denotes the probable distance of the electron from the nucleus. “n” is also known as the Principle Quantum number • Number of electrons that can fit in a shell: 2n2

6. s Orbital shape • The s orbital has a spherical shape centered around • the origin of the three axes in space. • Each s orbital can hold 2 electrons • Called the 1s, 2s, 3s, etc.. orbitals.

7. Sizes of s orbitals Orbitals of the same shape grow larger as n increases…

8. p orbitals • Start at the second energy level ( n=2 ) • 3 different directions • 3 different shapes (dumbbell shaped) • Each can hold 2 electrons , 6 total

9. d orbitals • Start at the third energy level (n=3) • 5 different shapes • Each can hold 2 electrons, 10 total

10. f orbitals • Start at the fourth energy level, (n=4) • Have seven different shapes • 2 electrons per orbital, total 14

11. Energy Levels, Suborbitals, Electrons

12. 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Increasing energy 3s 2p 2s 1s NUCLEUS

13. Electron Configurations • The way electrons are arranged in atoms. (an atom’s electron “address”) • The energy level and electron start filling from is lowest energy first (its ground state). • When we write electron configurations we are writing in the lowest energy.

14. Electron Configuration for Na… Sodium is element # 11, Na has 11 electrons that need to be put into an address: 1s2 2s2 2p6 3s1

15. Electron Configuration Notation # of electrons s 1 2 Energy Level (floor) Suborbital (apartment)

16. Let’s Practice Writing e- configurations: Don’t forget… • s suborbitals hold up to 2 electrons • p suborbitals hold up to 6 electrons • d suborbitals hold up to 10 electrons • f sub orbitals hold up to 14 electrons

17. Electron Configurations Rules that need to be followed when writing e- configurations: • Aufbau Principle - electrons enter the lowest energy first. • Pauli Exclusion Principle - at most 2 electrons per orbital – different/opposite spins!! • Hund’s Rule - When electrons occupy orbitals of equal energy they don’t pair up until they have to .

18. Rule # 1: AufbauUse the Aufbau diagram below

19. Aufbau Principle • Electrons fill the lowest energy orbitals first. • 4s will fill before 3d

20. Drawing Orbital Notation Configurations • A line or square is used to represent each orbital. • Arrows are used to represent each electron. • What element is represented in the ONC below?

21. Rule # 2 Pauli Exclusion Principle Each orbital can hold TWO electrons with opposite spins. (One electron is +, the other electron is - )

22. Rule # 3 Hund’s Rule Within a sublevel, place one e- per orbital before pairing them. RIGHT WRONG

23. 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Increasing energy 3s 2p 2s 1s Practice

24. Core Electrons Valence Electrons Notation Longhand Configuration S 16e- 2p6 2s2 1s2 3s2 3p4 Shorthand or Noble Gas configuration S 16e-[Ne]3s2 3p4

25. Electron Configurations and the Periodic Table

26. Orbital filling table

27. 1st column of s-block 1st Period s-block Electron Configurations using the Periodic Table Example - Hydrogen 1s1

28. Germanium 4s2 3d10 4p2 [Ar]