CHEMICAL BONDING and CHEMICAL INTERACTIONS

1. CHEMICAL BONDING and CHEMICAL INTERACTIONS PSc.2.2 OBJECTIVE: Understand chemical bonding and chemical interactions.

2. Objectives PSc.2.2.1 Infer valence electrons, oxidation number, and reactivity of an element based on its location on the Periodic Table.

3. Bonding and Molecules • The outer electrons are involved in bonding. • These are called valence electrons.

4. Bonding and Molecules • Most stable atoms have eight valence electrons. • When an atom has 8 valence electrons, it is said to have an octetof electrons.

5. The Octet Rule

6. Oxidation Number • An oxidation number indicates how many electrons are lost, gained, or shared when bonding occurs.

7. The elements in the A groups are called the representative elements. 8A0 1A 2A 3A 4A 5A 6A 7A

8. 1A • Group 1A elements haveonevalence electron. • They form1+ions after losing the one valence electron. • 1+ is referred to as theoxidation numberfor Group 1A elements.

9. Group 2A elements havetwovalence electrons. • They form2+ions after losing the 2 valence electrons. • 2+ is referred to as theoxidation numberfor Group 2A elements. 2A

10. Group 3A elements havethree valence electrons. • They form3+ions after losing the 3 valence electrons. • 3+ is referred to as theoxidation numberfor Group 3A elements. 3A

11. Group 4A elements havefour valence electrons. • They form4+ions after losing the 4 valence electrons. • They could just as easily form4-ions after gaining four additional electrons. 4A

12. Group 4A elements could have a 4+ or 4-oxidation number, depending on the element with which they are bonding. 4A

13. Group 4A • Two elements in Group 4A have multiple oxidation numbers of 2+ and 4+. • These two elements are tin (Sn) and lead (Pb).

14. Group 5A elements havefive valence electrons. • They form3-ions after gaining 3 additional electrons. • 3- is referred to as theoxidation numberfor Group 5A elements. 5A

15. Group 6A elements havesix valence electrons. • They form2-ions after gaining 2 additional electrons. • 2- is referred to as theoxidation numberfor Group 6A elements. 6A

16. Group 7A elements haveseven valence electrons. • They form1-ions after gaining 1 additional electron. • 1- is referred to as theoxidation numberfor Group 7A elements. 7A

17. Group 8A elements haveeight valence electrons, except helium which only has 2. • Group 8A elements, with a full complement of valence electrons, are generally not reactive. 8A

18. Question How many valence electrons are in an atom of each of the following elements? a) Magnesium (Mg) (2) b) Selenium (Se) (6) c) Tin (Sn) (4)

19. Question Determine the oxidation number of each of the following elements. a) Potassium (K) (1+) b) Chlorine (Cl) (1-) c) Tin (IV) (Sn) (4+)

20. Reactivity of Metals In general, the reactivity of metals increases from top to bottom and decreases from left to right.

21. Reactivity of Metals

22. Reactivity of Nonmetals In general, the reactivity of nonmetals increases from left to right and decreases from top to bottom.