3. Chemical Bonding What holds things together?

4. Bonding Involves the valence electrons or outermost electrons Outermost electrons in the last energy shell How many valence electrons does N have? Group 5A – 5 valence electrons

6. Bonding… Lewis dot structures show the valence electrons around at atom and for most molecules and compounds a complete octet for the elements N Al

7. Write out the electron configuration for the following atoms and ions: He Ne Ar Kr

8. NaCl NaCl + - electron transfer and the formation of ions ionic bond This is the formation of an ionic bond. Cl Cl 2 covalent bond This is the formation of a covalent bond. sharing of a pair of electrons and the formation of molecules

9. Ionic Bond Between atoms of metals and nonmetals with very different electronegativity Bond formed by transfer of electrons Produce charged ions all states. Conductors and have high melting point. Examples; NaCl, CaCl 2, K 2 O

11. Ionic Bonds: One Big Greedy Thief Dog!

12. 1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

14. COVALENT BOND bond formed by the sharing of electrons

15. Covalent Bond Between nonmetallic elements of similar electronegativity. Formed by sharing electron pairs Stable non-ionizing particles, they are not conductors at any state Examples; O 2, CO 2, C 2 H 6, H 2 O, SiC

17. Chlorine atom 2,8,7

18. 2 Chlorine atoms Outer shells only

19. Chlorine molecule Cl 2 Molecules have no overall electric charge Molecular or covalent compounds are usually gases or liquids – they have low melting points and low boiling points Forces between molecules very weak Forces (bonds) between atoms in the molecule very strong Each outer shell has 8 electrons Electrons shared

20. Covalent Bonds: Water H 2 O MethaneCH 4 AmmoniaNH 3 HydrogenH 2 Hydrogen ChlorideHCl OxygenO 2 N.B. Oxygen has a double bond

21. Oxygen O 16 8 Oxygen atom 2,6

22. 2 Oxygen atoms (outer shells only) Double covalent bond O O

23. More sharing examples O2O2 N2N2 O ONNOOO O NNNN NN double bond (2 pairs) triple bond (3 pairs) Share until octet is complete. octet complete

24. NH 3 NH H H normal covalent bond (each atom supplies an electron) Some more sharing examples

25. ioniccovalent valence electrons Comparison of Bonding Types sharing of electrons transfer of electrons ions molecules conductive non- conductive