Nonmetals

1. Nonmetals Ashton Lokar AP Chem

2. Hydrogen (H) Helium(He) Carbon (C) Nitrogen (N) Oxygen (O) Fluorine (F) Neon(Ne) Phosphorus (P) Sulfur (S) Chlorine (Cl) Argon (Ar) Selenium (Se) Bromine (Br) Krypton (Kr) Iodine (I) Xenon (Xe) Radon (Rn) The Nonmetals are:

3. Reactivity of Nonmentals • Nitrogen is least reactive due to triple bonds that hold the N2 molecule together • A large exothermic reaction occurs giving off hundreds of kilojoules of energy when the N2 molecule is broken, this is why explosives commonly contain nitrogen

4. Reactivity of Nonmetals (cont.) • Fluorine is the most reactive element because of the weakness of the single bond in the F2 molecule • It has an E * red of +2.889 V • It bonds with all elements except for He, Ne and Ar • It even bonds with water which means reactions of compounds containing fluorine reacting with water cannot occur

5. Reactivity of Nonmetals (cont.) • Chlorine is slightly less reactive than fluorine • It still reacts with most metals • Heat is often required to induce reactions

6. Occurrence and preparation • 3 Nonmetals: oxygen, nitrogen and sulfur occur in nature such as in the earth and in the air • Fluorine is found in minerals • Chlorine is found in underground deposits of rock salt • Bromine is found in brine wells

7. Allotropy • By definition allotropy is when two or more structural forms of an element in the same phase occur in a reaction • Ex. 2O3(g) -> 3O2(g) • Phosphorus has several allotropes • 2 most common: red phosphorus and white phosphorus • Sulfur can have more than 20 allotropic forms in its solid state, this is done by solid sulfur forming different crystalline structures • Ex. S8(rhomibic)-> S8(monoclinic)

8. Examples of Allotropy Problems • For the allotropic conversion P(white)-> P(red) H is -17.6 KJ and S is -18.3 J/K At what temperature are the two allotropes in equilibrium? • Taking that H = TS : • T= H/S = -17.6 KJ/-.0183KJ/K = 962K or 690 degrees C

9. Hydrogen Compounds of the Nonmetals (Classified by Group)

10. Oxygen Compounds of Nonmetals

11. Reactions of Nonmetal Oxides with Water • When many nonmetals react with water acids are formed • These acids are called acid anhydrides • Ex: SO3(g) +H2O(l) -> H2SO4(l)

12. Oxoacids and Oxoanions

13. Acid Strength • Increasing Oxidation number of the central atom (HClO< HClO2< HClO3<HClO4) • Increasing electronegativity of the central atom (HIO<HBrO<HClO) • X is a highly electronegative atom such as Cl • Additional, strongly electronegative oxygen atoms are bonded to X

14. Oxidizing and Reducing Strength • A species in which a nonmetal is in its highest oxidation state can act only as an oxidizing agent, never as a reducing agent. Ex: ClO4 – ion, where chlorine is in its highest oxidation state, +7 • A species in which a nonmetal is in an intermediate oxidation state can act as either an oxidizing agent or a reducing agent Ex: ClO3- is a much stronger oxidizing agent (E*red = +1.442 V) than reducing agent (E*ox = -1.226 V)

15. Oxidizing and Reducing Strength (cont.) 3. Sometimes, with a species such as ClO3-, oxidation and reduction occur together, resulting in disproportionation: Ex: 4ClO3-(aq) -> 3ClO4-(aq) +Cl-(aq) E* = +0.216 V In general a species in an intermediate oxidation state is expected to disproportionate if the sum E*ox +E*red is a posotive number

16. Oxidizing and Reducing Strength (cont.) • 4. The oxidizing strength of an oxoacid or an oxoanion is greates at high [H+] (low pH). Conversely, its reducing strength is greatest at low [H+] (high pH) • - when ClO3- acts as an oxidizing agent, the H+ ion is a reactant, so increasing its concentration makes the process more spontaneous • - when ClO3- acts as a reducing agent, the H+ ion is a product; to make the process more spontaneous, [H+] should be lowered