Chemical Bonding

1. Chemical Bonding Joining atoms together to make compounds

2. Chemical Bonding: combining atoms of elements together to form new substances • Bond: force that holds atoms together to form molecules

3. Molecules • Two or more atoms that form a new substance • Smallest part of a compound

4. Review of atomic structure • Atoms: electrons, protons, neutrons • Electrons are negatively charged • Protons are positively charged • Neutrons have no charge • Electrons are in energy levels • First level = 2 electrons • Second level = 8 maximum electrons • Third level = 18 maximum electrons

5. Valence electrons: the outermost electrons • Determine how and with what the atom will bond • Electrons and energy levels video

6. FACT: Atoms become stable (won’t react chemically) when they have a full outer energy level.

7. Bohr model review • Start with a circle (nucleus) • Put in proper number of protons (atomic number) • Calculate number of neutrons • Atomic mass – mass of protons = neutrons • Place electrons: • Start in inner ring, fill first then move to next • Start at “12:00”, then “3”, then “6”, then “9” • Once shell is half full, electrons pair up

8. Electron Dot Diagrams • Electron dot diagrams used to show how many valence electrons are in an element Rules: • Start with the symbol for the element • Represents nucleus and “inner” energy levels • Count how many valence electrons are in the outer shell • Place one dot at a time working around the symbol, usually start at “3:00” position o- -

9. Electron dot diagramsExamples

10. Octet Rule: Fill the outer shell to give a total of 8 shared electrons • Makes a stable molecule, will not react further

11. Types of Bonds • Ionic Bonds: transfer of electrons from one atom to another • Ions: Positively or negatively charged atoms • Since negatives and positives attract, the atoms bond to each other • Usually happens between a metal and a nonmetal • Ionic Bonding video

12. Which elements do you think will bond together?

13. e e e e e e e e e e e e e e e e e e e e e e 11P 17P 12N 18N e e e e e e Na Cl

14. e e e e e e e e e e e e e e e e e e e e e e 11P 12N 17P 18N e e e e e e + Na Cl –

16. + Na Cl –

17. Na Cl

18. Salt video

19. Covalent bonding: Sharing electrons equally between two or more atoms • Example: Hydrogen has one valence electron so it needs one more to fill up its energy level • Covalent bonds often happen between like elements • Usually happens in non-metals • Cl2, H2, O2 Covalent Bonds video

21. e e e 6P e e e 6N 1P e C H

22. e e e 6P e e e 6N e e 1P 1P 1P 1P e e

23. e e e 6P e e e 6N e e 1P 1P 1P 1P e e

24. e e 6P 6N 1P 1P 1P 1P C H 4 e e e e e e e e

25. C H 4

26. Structural Formula: • shows the actual arrangement of the molecule • replace dots between atoms with lines to indicate the bonds