The Representative Elements

1. The Representative Elements Ch 18 & 19

3. Representative Elements • Their chemical properties are determined by their valence (s and p) electrons. • Properties are similar within a group, but first element in a group tends to act differently due to smaller size. • Most abundant element is oxygen, followed by silicon. • Most abundant metals are aluminum and iron, which are found as ores.

4. Group 1 (1A) – Alkali Metals • Have Valence electron configuration ns1 • Will lose 1 electron to form M+ Ions • React vigorously with water to form M+ and OH- ions and hydrogen gas. • React with oxygen to form oxides. Lithium will form a regular oxide (Li2O) while sodium will form a peroxide (Na2O2). Potassium, rubidium and cesium form superoxides (MO2)

6. Hydrogen • Can form covalent compounds with other nonmetals. • Will form salts, hydrides, with very active metals (group 1A and 2A). • Hydride ion, H-, is a strong reducing agent. • Covalent hydrides form when hydrogen bonds with other nonmetals. • Metallic hydrides occur when hydrogen atoms migrate into transition metal crystals.

7. Group 2 (2A) – Alkaline Earth Metals • Have valence electron configuration ns2 • Called Alkaline earth because of the basicity of their oxides. • React less vigorously with water than group 1. • Heavier alkaline earth metals form ionic nitrides and hydrides. • Hard water is caused by the presence of Ca+2 and Mg+2 ions.

9. Group 13 (3A) • Have valence electron configuration ns2 np1 • Show increasing metallic character goingdown the group. • Boron forms covalent compounds with hydrides called boranes. These compounds are highly electron deficient and very reactive. • Aluminum has some covalent characteristics as do indium and gallium. • Thallium is completely metallic in character.

11. Group 14 (4A) • Have valence electron configuration ns2 np2 • Show a change from nonmetallic to metallic properties going down the group. • All elements in this group form covalent bonds with nonmetals. • MX4 compounds (except carbon)react with Lewis bases to form two additional covalent bonds.

13. Group 15 (5A) • Have varied chemical properties. • All members except nitrogen form molecules with 5 covalent bonds. (Nitrogen has no d sublevel) • Nitrogen and Phosphorous are nonmetals and form 3- anions in salts with active metals. • Antimony and bismuth are metallic. However their 5+cations tend to be molecular rather than ionic.

14. Nitrogen • The strength of the triple bond in the N2 molecule is important both thermodynamically and kinetically as they decompose exothermically. • The nitrogen cycle is the process through which nitrogen is recycled through the environment. • Nitrogen forms a series of oxides in which it has an oxidation state ranging from 1 to 5. • Nitric acid is a strong acid which is important as a reducing agent. • Ammonia is the most important nitrogen hydride. • Has pyramidal molecules with polar bonds. • Hydrazine (N2H4) is a powerful reducing agent.

15. Phosphorous • Exists in three elemental forms: white, black and red. • Phosphine (PH3) has a structure analogous to that of ammonia but with bond angles closer to 90o. • Forms two oxides with oxidation states of 3+ and 5+.

16. Group 16 (6A) • Shows the usual tendency of increasing metallic properties going down the group. • None behave as typical metals • Achieve noble gas configurations by adding two electrons to form 2- anions. • Form covalent bonds with other nonmetals. • Oxygen exists in two elemental forms: O2 and O3. • Sulfur has two elemental forms, both of which contain stacks of S8 rings. • Sulfur also forms two oxides: SO2 and SO. • Sulfur forms a variety of compounds in which it has a +6, +4, +2, 0 or -2 oxidation state.

17. Group 17 (7A) - Halogens • This group consist of all nonmetals. • Form hydrogen halides (HX) that behave as strong acids in water, except for hydrogen fluoride. • Oxyacids of the halogens become stronger as the number of oxygen atoms attached to the halogen increase. • Interhalogens are compounds of two different halogens • Halogen-carbon compounds are important industrially: examples are Teflon, PVC and the Freons.

18. Group 18 (8A) – Noble Gases • Full valence shells ns2 np6 • Generally unreactive. • Krypton, xenon and radon will form compounds with the highly electronegative elements fluorine and oxygen.

19. Transition Elements Ch 20

20. The last electron in transition metals occupy the d sublevel. Because these inner orbitals cannot participate as easily in bonding as the s and porbitals the chemistry is not greatly affected by the gradual change in the increased number of electrons in the d orbital.

21. Have metallic physical and chemical properties. • In forming ionic compounds with nonmetals, the transition metals exhibit several typical characteristics: • More than one oxidation state is usually found • Cations are often complex ions • Most compounds are colored • Most compounds have paramagnetic properties

22. Transition metals form a variety of ions by losing one or more of their electrons. • The maximum possible oxidation state for a given transition element corresponds to the loss of all the s and d electrons. • Transition metals form coordination compounds which consist of complex ions and counter ions. • These coordination complexes are very important to biological chemistry.

24. Naming Coordination Compounds • The cation is named before the anion • The ligands are named before the metal ion • An o is added to the root name of an anion in the ligand • Prefixes are used to denote the number of simple ligands • The oxidation state of the central metal ion is designated by a Roman numeral in parenthesis • If more than one ligand is present, name them alphabetically (prefixes do not count) • If complex ion has a negative charge, the suffix –ate is added to the name of the metal