median lethal dose (LD50)

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1 Monday, October 22 Lecture 16 (Thursday) 5 min on Sec=ons 4.4 and 4.5 Ions (5.1) Ionic Compounds (5.2) Naming Ionic Compounds (5.3) Polyatomic Ions (5.4) Lecture 17 (Monday) Polyatomic Ions (5.4) Covalent Compounds (5.5) Naming and Wri=ng Covalent Formulas (5.6) Electronega=vity and Bond Polarity (5.7)

2 Exam #1: A Few Notes Understand the concept of median lethal dose (LD 50 ) know which type of measurement is described by each unit (g = mass, L = volume, etc) Exam format: 15 mul=ple choice Qs = 45 points 5 short to medium answer Qs = 45 points 1 long answer Q = 10 points Must show all work on non- mul=ple choice, non- fill in the blank ques=ons to get credit (or par=al credit) You will receive periodic table conversion factors equa=ons

3 Ionic and Covalent Bonds Atoms form octets to become more stable. by losing, gaining, or sharing valence electrons. by forming ionic or covalent bonds Pearson Educa=on, Inc. Chapter 5, Sec=on 1 3

4 Overview of Ions, Ionic Compounds, and Covalent Compounds Ma^er Pure Substances Mixtures Elements Compounds Homogeneous Heterogeneous There are a few types of compounds

Compounds Covalent Compounds are made of

Nonpolar Covalent Compounds H 2 (g) Form

5 Overview of Ions, Ionic Compounds, and Ionic Compounds Covalent Compounds Compounds Covalent Compounds are made of discrete molecules (groups of connected atoms) NaCl (s) monatomic ions polyatomic ions Polar Covalent Compounds Nonpolar Covalent Compounds H 2 (g) Form a repea=ng network e not shared H 2 O (l) e shared equally

6 Ionic and Covalent Bonds Atoms form octets to become more stable. by losing, gaining, or sharing valence electrons. by forming ionic or covalent bonds Pearson Educa=on, Inc. Chapter 5, Sec=on 1 6

7 Ionic Compounds The transfer of an electron from Na to Cl results in two oppositely- charged ions that each have a complete octet in their valence shells. The ionic bond is due to the electrostafc agracfon between Na + and Cl. An ionic solid consists of an extended network of anions and ca5ons.

8 Naming Ionic Compounds CaFons (M n+ ): name of atom + ca5on Magnesium: Mg magnesium ca5on Cesium: Cs +... cesium ca5on For metals that can form more than one kind of ca5on, use Roman numerals to indicate charge Iron: Fe iron(ii) ca5on Fe iron(iii) ca5on Chromium: Cr chromium(ii) ca5on Cr chromium(iii) ca5on Anions (X m- ): root of atom name + - ide Fluorine: F -... fluoride anion Sulfur: S sulfide anion Selenium: Se selenide anion Compound Name: <ca=on name> <anion name> Chemical Formula: M m X n : Al 2 O 3, MgCl 2, MgO ( Mg 2 O 2 )

9 Naming Examples Name the following compounds: KCl potassium chloride CaBr 2 calcium bromide CuCl copper(i) chloride MnO 2 manganese(iv) oxide Write formulas for the following: barium hydride BaH 2 aluminum sulfide Al 2 S 3 vanadium(v) fluoride VF 5 =n(iv) bromide SnBr 4 9

10 Ionic Compounds with Polyatomic Ions Wri=ng names and formulas is pre^y much the same as for binary compounds ca=on is named first, anion is named second mul=ples of the ions are taken to ensure charge neutrality Example: Na 2 SO 4 2Na + + SO 4 2- à sodium sulfate manganese(ii) hydroxide Mn OH - à Mn(OH) 2 The tricky part is learning where one ion ends and the next begins. Example: KHSO 4 K + + HSO 4 - à potassium hydrogen sulfate NH 4 C 2 H 3 O 2 NH 4+ + C 2 H 3 O 2 - à ammonium acetate NaH 2 PO 3... Na + + H 2 PO 3 - à sodium dihydrogen phosphite Lucky for you guys, there are only a few common polyatomic ca7ons: NH 4 + and Hg

11 From the following list select the element that is most likely to become an anion during a chemical reac=on. 1. Hydrogen (H) 2. Calcium (Ca) 3. Carbon (C) 4. Bromine (Br) Nonmetals tend to gain electrons in reac=ons. 11

12 Choose the answer for the element that is most likely to form a cafon, and has the correct charge listed 1. N with 3 charge 2. Ne with +1 charge 3. Al with +3 charge 4. Na with +2 charge. Nitrogen does not give up electrons easily; N forms anions Neon is a noble gas and does not form ions easily Metals tend to lose electrons in reac=ons. Aluminum is in group 3 Sodium forms monoca=ons, not dica=ons 12

13 Polyatomic Ions Know these!! 4 th edi=on = p. 171

14 Rules for Naming Polyatomic (PA) Ions Similar PA ions have the same base name like a root word or base units of measurement ex: - chlor- for PA ions containing Cl and O - nitr- for PA ions containing N and O prefixes and suffixes are used to describe the different PA ions within groups: per ate highest O content ClO 4 per ate usually most common PA ion in family ClO 3 per ite lower O content than ate ClO 2 hypo ite lowest O content ClO LEARN THESE RULES 14

15 Rules for Naming Polyatomic (PA) Ions (2) Some PA ions can have variable amounts of H cafons When H cafons are part of PA anions, 1) the charge of the PA anion increases by 1 2) the prefixes hydrogen or bi are used: carbonate = CO 2 3 hydrogen carbonate = HCO 3 = bicarbonate sulfate = SO 2 4 hydrogen sulfate = HSO 4 = bisulfate phosphate = PO 3 4 hydrogen phosphate = HPO 2 4 dihydrogen phosphate = H 2 PO 4 15

16 Copper Sulfate: An Ionic Compound with a Polyatomic Anion Copper(II) sulfate, CuSO4 O Cu2+ O S O O O O S O O 16

17 Ionic Compounds with Polyatomic Ions Wri=ng names and formulas is exactly the same as for binary compounds ca=on is named first, anion is named second charges must balance! Example: Na 2 SO 4 2Na + + SO 4 2- à sodium sulfate manganese(ii) hydroxide Mn OH - à Mn(OH) 2 KHSO 4 K + + HSO 4 - à potassium hydrogen sulfate ammonium sulfide 2 NH 4+ + S 2 à (NH 4 ) 2 S FePO 4... Fe 3+ + PO 4 3- à iron(iii) phosphate aluminum acetate Al CH 3 COO à Al(CH 3 COO) 3 17

18 Covalent Compounds In a covalent bond, electrons are shared between the atoms rather than transferred. H.. H H H Note that this line represents a pair of electrons. The driving force for covalent bond forma5on is to again a full outer- most electron shell.

19 Formulas of Elements The chemical formula of most elements is the atomic symbol, e.g. Li, Os, Xe, Pu Some elements form diatomic molecules. Memorize these: H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2 Horses Need Oats For Clear Brown I s Other excep=ons: P 4, S 8, C 60 19

20 Binary Covalent Compounds CO CO 2 BF 3 HCl H 2 O H 2 O 2 (two nonmetals, or a nonmetal and a metalloid) 1. The first element in the formula is named first, and the full element name is used. 2. The second element is named as though it were an anion. 3. Prefixes are used to indicate the number of atoms present. 4. The prefix mono- is never used for naming the first element. i.e., CO is carbon monoxide, not monocarbon monoxide. Prefix # Indicated mono- 1 di- 2 tri- 3 tetra- 4 penta- 5 hexa- 6 hepta- 7 octa- 8 nona- 9 deca- 10

21 Example Name the following compound: BF 3 boron trifluoride Name the following compound: I 2 O 7 diiodine heptoxide Write the formula for: phosphorus trichloride PCl 3 Write the formula for: dinitrogen trioxide N 2 O 3 21

22 Lewis Dot Structures (LDS) A Lewis structure is a 2D representa=on of the bonding pa^ern in a molecule. Central idea: the most stable arrangement of electrons is one in which all atoms have a noble gas configura=on (the octet rule). Bonding Pair Lone Pair An atom typically forms as many bonds as it has holes in its valence shell. Three basic steps for drawing Lewis structures: 1. Sum the valence electrons for all atoms to determine total number of electrons. 2. Use pairs of electrons to form a bond between each pair of atoms (bonding pairs). 3. Arrange remaining electrons around atoms (lone pairs and/or mul=ple bonds) to safsfy the octet rule for each atom ( duet rule for hydrogen).

Chapter 2. Law of Definite Proportions. Law of Definite Proportions. Law of Conservation of Mass 10/7/2011 WATER H 2 O

Chapter 2. Law of Definite Proportions. Law of Definite Proportions. Law of Conservation of Mass 10/7/2011 WATER H 2 O Chapter 2 Fundamental Chemical Laws (2.2) Dalton s Atomic Theory (2.3) Defining the Atom (2.5) Atomic Structure (2.6) Molecules and Ions (2.7) The Periodic Table (2.8) Nomenclature (2.9) Law of Conservation