The Periodic Table

1. The Periodic Table

2. Phases of Matter Solids • Atoms tightly bound • Fixed volume and shape (does not conform to container) • A chemical is denoted as solid by labeling it with (s) S(s)

3. Phases of Matter Liquids • Atoms less tightly bound than solids • Has a definite volume, but not definite shape (assumes the shape of its container) • Denoted by (L) H2O (L)

4. Phases of Matter Gases • Free atoms • No shape, no definite volume • Can be expanded or compressed (like engine piston) • Denoted by (g) ; ex. O2 (g)

5. Elemental Classifications • Elements can be metals, nonmetals, or semiconductors(intermediates between metals and nonmetals) • Physical Characteristics of Metal • Solids at room temperature (except Mercury) • Malleable and ductile • Conductive of electricity and heat • Have luster and shine • Very High Melting Points

6. Elemental Classifications Physical Characteristics of Nonmetals • Non conductive • Most are gases, but some are solid. The solids tend to be brittleand powdery • Low melting points He (g) S(s)

7. All elements LEFT of the black line are treated as metals, except Hydrogen.

8. Chemical Groups and Diatomic Molecules • Certain elements are unstable, and hence, do not commonly exist as individual neutral species, but rather as diatomic molecules • These include H, O, N, and all of the halogens (group 17) H  H2 (Hydrogen gas) O  O2 (Oxygen gas) N  N2 (Nitrogen gas) F, Cl, Br, I  F2, Cl2, Br2, I2 (Fluorine (g), chlorine (g), bromine (L) and iodine (s))

9. Nomenclature: Ionic Compounds • Example • KF Potassium Fluoride • Molecules are formed by atomic bonding. For purposes of naming, we consider two types of molecules: IONICand COVALENT. Special rules exist for naming molecules of each type. • Ionic “bonds” form between metal ions and nonmetal ions • To name an ionic compound, you do the following • Write the name of the metal • Follow it with the ionic name of the nonmetal ion

10. Nomenclature: Covalent Compounds • Examples • CO carbon monoxide • N2S dinitrogensulfide • CO2carbon dioxide • P4Se10tetraphosphorusdecaselenide • Covalent bonds form between nonmetals • To name an covalent compound: • Write the name of the first nonmetal. For non-unity subscripts, use greek prefixes (shown on right) • Follow that with the ionic name of the second nonmetal. Again, include greek prefixes. Only use mono- for oxygen containing molecules.

11. Nomenclature: The Strange Rules of Hydrogen • Hydrogen chalcogenides and halides are named according to ionic rules, if the hydrogen is listed first. Ex. H2S (g) = hydrogen sulfide; HF (g) = Hydrogen Fluoride • Hydrogen halides dissolved in water(anything dissolved in water is called an “aqueous solution”, abbreviated “aq”) are acidsand are named as such. • We drop –gen and end the second nonmetal with the suffix “–icacid” HCl(aq) = hydrochloric acid ; HF (aq) = hydrofluoric acid • If hydrogen is listed last, it is a hydride anion (H-). The name is ionic or covalent depending on what it is paired with. Ex. MgH2= magnesium hydride (ionic); TeH2= telleriumdihydride (covalent)

12. Conservation of Mass • All chemical reactions obey the law of conservation of mass. • Therefore, in a chemical reaction, atoms are merely rearranged to create new molecules. The total mass of matter present at the end of a reaction must equal the mass present at the beginning. • You can not create elements via chemical reaction! Matter can not created or destroyed.

13. Chemical Reactions • As you can see from the chemicalequationshown to the left, productstypically exhibit vastly different characteristics the reactants • Also recall our discussion on the law of conservation of mass. Based on this law, can you find a problem with the equation written shown?

14. Balanced Reactions • Mass can not be created or destroyed. This means that every element contained in the reactants must be accounted for in the product(s) • There are two chlorine atoms on the reactant side, and only one chlorine atom one the product side. To balance the chlorine atoms, we add a coefficientof 2 to the product side • We now add a coefficient of 2 to the Na (s). The reaction is now balanced.

15. Coefficients And Subscripts • The balanced equation above says that two Na atoms react with one chlorine gas moleculeto produce two molecules of NaCl • The coefficientof 2 means that there are two separate Na atoms • The subscriptof 2 indicates two Cl atoms bonded together in a single molecule • Do not confuse coefficients and subscripts. Do not alter subscripts when balancing. NaCl Na Cl Cl NaCl Na

16. Tips For Balancing Reactions • Before carrying out any calculations, it is imperative that you first confirm that a given chemical equation is balanced. • The rules for balancing a chemical equation are provided below. • First, balance those elements that appear only once on each side of the equation • Balance the other elements as needed. Pay attention to subscripts. • Include phases

17. Tips For Balancing Reactions • Let’s balance the equation below using the rules from the previous slide. C3H8 (s) + O2 (g) C3H8 (s) + O2 (g) C3H8 (s) + O2 (g) C3H8 (s) + 5 O2 (g) CO2 (g) + H2O (L) 3 CO2 (g) + H2O (L) 3 CO2 (g) + 4 H2O (L) 3 CO2 (g) + 4 H2O (L) • We’ll balance C first. • Now balance H. • Now balance O.

18. Group Work • Balance the following reactions: Sulfur trioxide (g)  Sulfur dioxide (g) + Oxygen (g) Dichlorineheptaoxide (g) + Water (L)  Hydrochloric acid (aq) + Oxygen (g) C4H10(g) + Oxygen (g)  Carbon Dioxide (g) + Water (g)