Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28General Chemistry Topic 3:Chemical Compounds, Ionic and Covalent BondsObjectives: By the end of this topic, you should: 1. Understand the difference between ionic and molecular compounds. 2. Know a little bit about Lewis structures and why they are useful in visualizing chemical bonds and compounds.  3. Be familiar with the Octet rule and its usage in explaining why certain elements tend to form ionic compounds versus molecular compounds 4. Understand the nature of ionic, covalent, and polar covalent bonds, and be able to classify compounds with regard to their type of bonds. 5. Understand and be able to recognize monovalent, divalent, and polyatomic ions, as well as anions and cations.  6. Understand the difference between a compound and a mixture, and know the three types of mixtures (solutions, colloids, and suspensions).  7. Understand the nature of partial charges and nonpolar, polar, and hydrogen bonds. Suggested reading: Denniston et al., Chapter 3, pp. 83--112 (pp. 83-112)Homework problems: 3.21 (3.21), 3.23 (3.23), 3.29-3.32 (3.29-3.32), 3.43-3.45 (3.43-3.45)Additional problemsPredict whether the bond formed between each of the following pairs of atoms would be ionic, nonpolar, or polar covalent:a. S and Ob. Si and Pc. Na and Cld. Na and Oe. Ca and BrPredict whether the bond formed between each of the following pairs of atoms would be ionic, nonpolar, or polar covalent:a. Cl and Clb. H and Hc. C and Hd. Li and FAtomic number = charge of an atom = # of protons (# of+ charges). Atomic number defines the elementAtomic mass (atomic weight) = # of protons + # of neutronsAtoms are electrically neutral, so # of electrons = # of protons Chemical properties of atoms determined by electron configurations. Valence (outer shell) electrons are the major players.Atomic symbolsH11atomic massatomic numbersymbol of elementp+e-Hydrogen atom6p+6n0 6e-Carbon atomAtomic number = 1Atomic mass = 1Atomic number = 6Atomic mass = 12H11C12 6Review: Elements and AtomsForgetabouttheseelementsForget aboutthese elements too8 columns (families)213 76548Care about first 20 elements4 Rows(periods)Noble gasesValence e-everything(almost)REVIEW - The Periodic Table of ElementsElectrons at the outermost level (shell) are called valence electrons.They determine chemical stability/reactivity of a substance.The Noble gases (group VIIIA) have their outermost level completely filled with electrons.Noble gases are chemically inert (least reactive among the elements). Family Atomic Principal level number (columns) Elements number 1 2 3 4 Group IA Lithium 3 2 1Alkali metals Sodium 11 2 8 1Potassium 19 2 8 8 1Group IIA Beryllium 4 2 2Alkali earth Magnesium 12 2 8 2 metals Calcium 20 2 8 8 2Group VIIA Fluorine 9 2 7 Halogens Chlorine 17 2 8 7Group VIIIA Helium 2 2 0Noble gases Neon 10 2 8 0Argon 18 2 8 8 0Electron configurations among four families of representative elementsAtoms of the reactive elements tend to undergo chemical reactions that lead to electron configurations of the nearest noble gas. Atomic Electron configuration Electron configuration Nearest # of atoms of ions noble gasGroup Elements 1 2 3 4 5 Ions 1 2 3 4 5 IA Li 3 2 1 Li+ 2 Helium Na 11 2 8 1 Na+ 2 8 Neon K 19 2 8 8 1 K+ 2 8 8 Argon IIA Mg 12 2 8 2 Mg+2 2 8 Neon Ca 20 2 8 8 2 Ca+2 2 8 8 Argon VIA O 8 2 6 O–2 2 8 Neon S 16 2 8 6 S–2 2 8 8 Argon VIIA F 9 2 7 F– 2 8 Neon Cl 17 2 8 7 Cl– 2 8 8 Argon Br 35 2 8 18 7 Br– 2 8 18 8 Krypton I 53 2 8 18 18 7 I– 2 8 18 18 8 XenonVIIIA He 2 2 0Noble Ne 10 2 8 0gases Ar 18 2 8 8 0 The noble gases do NOT form stable ions Kr 36 2 8 18 8 0 Xe 54 2 8 18 18 8 0Formation of ions (atoms that have lost or gained electrons) shown belowlose 1 e-lose 2 e-gain 2 e-gain 1 e-outer shellfullouter shellfullouter shellfullOuter shell already fullouter shellfullReview: The Octet RuleGroup Number (columns in Periodic Table) 1 2 3 4 5 6 7 81e-2e-3e-4e-5e-6e-7e-8e-H HeLi Be B C N O F NeNa Mg Al Si P S Cl ArK CaNumberofValenceElectronsA convenient way to visualize valence shell electrons.Useful for figuring out how atoms will behave.MetalsNonmetalsMetal vs. nonmetal is important for predicting how atoms will react.Electron dot (Lewis) structuresMetalloids – some properties of bothCompound: two or more atoms of different elements joined by attractive forces, i.e., chemical bonds.Molecules – 2 or more atoms joined by covalent bond(s)•Ionic – attraction between oppositely charged ions that resultsfrom transfer of electrons, e.g., NaCl, MgCl2)•Covalent – sharing of valence electrons by atomse.g., O2, Cl2, H2O, C6H12O6 - nonpolar – equal sharing of electrons - polar – unequal sharing of electronsBond types:Chemical bonding is a function of gain, loss, or sharing of electrons. Only valence electrons (outermost shell) involved.Type of bond formed governed by octet rule - # of electrons required to fill outer shell.Chemical Compounds – An OverviewMetals tend to lose electrons to form positively charged ions (cations). Cations react with anions of nonmetals to form ionic compounds. Metals tend not to react with each other.Nonmetals tend to gain electrons to form negatively charged ions (anions) which can react with metal cations to form ionic compounds.Nonmetals can also combine with one another (or themselves) to form covalent compounds (sharing electrons between two atoms).Governs the types of bonds they tend to form and the atoms they tend to react withAtoms like to have their outer electron shell filledIonic bonds fill the outer shells of reacting atoms by transfer of e-Covalent bonds fill the outer shells of reacting atoms by