Electrons in Atoms

1. Electrons in Atoms

2. Bohr’s Model • Electrons move like planets around the sun. • In circular orbits at different levels. • Amounts of energy separate one level from another.

3. The Bohr Model of the Atom • Electrons of hydrogen circle the nucleus in orbits 1. orbits have a fixed amount of energy in the ground state 2. orbits are a fixed distance from the nucleus 3.orbits furthest from the nucleus have the greatest energy

4. 4. Electrons in the ground state can absorb quanta of energy – become excited- and move to a higher orbit 5. Electrons emit quanta of energy when they return to the ground state 6. Model applies only to hydrogen atoms

5. Niels Bohr (1885 – 1962) Bohr Model of the Atom

6. Bohr’s Model Nucleus Electron Orbit Energy Levels

7. Bohr’s Model } • Further away from the nucleus means more energy. • There is no “in between” energy • Energy Levels Fifth Fourth Third Increasing energy Second First Nucleus

8. Bohr • Make a model of Bohr’s Hydrogen. Bohr was only correct about Hydrogen. • Draw a nucleus • Then draw the electron.

9. Changing the energy • Let’s look at a hydrogen atom

10. Changing the energy • Heat or electricity or light can move the electron up energy levels

11. Changing the energy • As the electron falls back to ground state it gives the energy back as light

12. Changing the energy • May fall down in steps • Each with a different energy

13. II.Heisenberg Uncertainty Principle • It is impossible to know exactly the position and velocity of a particle at the same time. • The better we know one, the less we know the other. • The act of measuring changes the properties. • Look at the fan

14. Covalent clip

15. I.The Covalent Bond A. Why do atoms form bonds? 1. To get 8 valence shell electrons (noble gas configuration) 2. more stable configuration - less potential energy B. Definition of Covalent Bond 1. bond resulting from sharing electrons 2. share electrons by overlapping of orbitals

16. I.The Covalent Bond A. Why do atoms form bonds? 1. To get 8 valence shell electrons (noble gas configuration) 2. more stable configuration - less potential energy B. Definition of Covalent Bond 1. bond resulting from sharing electrons 2. share electrons by overlapping of orbitals

17. Covalent Bonds – Sharing of Electrons

18. The Lewis dot structure for Oxygen O Oxygen is in group VIA so it has 6 valence electrons

19. The Lewis dot structure for Chlorine Cl chlorine is in group VIIA so it has 7 valence electrons

20. The Lewis dot structure for calcium Ca calcium is in group IIA so it has 2 valence electrons

21. Ca + Cl Cl Ca( Cl )2 Making calcium chloride

22. H H H Lewis dot structure of a compound NH3 N

23. Lewis dot structure of a compound NH3 • How many valence electrons does N have? N is in group VA so it has 5 valence electrons 2) How many valence electrons does H have? H is in group IA so each H has one valence electron 3) How many valence electrons does Neon have.

24. H O Water - H2O Each hydrogen has 1 valence electron Each hydrogen wants 1 more The oxygen has 6 valence electrons The oxygen wants 2 more They share to make each other happy

25. O Water • Put the pieces together • The first hydrogen is happy • The oxygen still wants one more H

26. O Water • The second hydrogen attaches • Every atom has full energy levels H H

27. Lewis structure • 1. PH3 • 2. H2S • 3. HCl • 4. CCl4 • 5. SiH4

28. Lesson 3Lewis structure • Use molecular model kit to build • 1. PH3 2. H2S • 3. HCl 4. CCl4 • 5. SiH4 6. CH4 • 7. ClF3 8. PCl5 • 9. SO2 10. N2O5

29. ClF3 • PCl5 • SO2 • N2O5

30. Isomers- Build the molecule On the right using springs for double bonds.

31. 3. diatomic molecules (contain two atoms) a. periodic table (1,1-7--->group 17) elements that form diatomic molecules H2 N2 O2 F2 Cl2 Br2 b. compounds can also be diatomic HCl CO NO HF HI HBr

32. C. Examples and Diagrams H2 F2 HF Make a drawingD. What is a molecule? 1. two or more atoms bonded covalently 2. examples- Make a drawing (usually two or more nonmetals) H2O NH3 CH4 N2O5 HCl C6H12O6