Chapter 4

Chapter 4

Chapter 4 Covalent Compounds Dalton Trans., 2016,45, 15481-15491 Covalent Compounds

Covalent Compounds: compounds composed of atoms bonded to each other through the sharing of electrons Electrons NOT transferred No + or charges on atoms Non-metal + Non-metal Also called molecules Examples: CO2

Cl2 CH4 Dihydrogen Monoxide (DHMO)!!!!!! Properties Deadly, colorless, odorless liquid Hazards!!! Can mutate DNA!! Death due to accidental inhalation of DHMO, even in small quantities. Prolonged exposure to solid DHMO causes

severe tissue damage DHMO is a major component of acid rain Contributes to soil erosion. Dihydrogen Monoxide H2O, commonly known as water Can mutate DNA!! water can get ionized to react with DNA Death due to accidental inhalation of DHMO, even in small quantities--- when

someone drowns Prolonged exposure to solid DHMO causes severe tissue damage--- Ice DHMO is a major component of acid rain Contributes to soil erosion--- water corrodes the landscape over time Covalent Bonding or Duet or

H-H Naming Covalent Compounds 1) Name the first non-metal by its elemental name 2) Add a prefix to indicate how many mono 6 hexa 3) If only1one atom, dont put mono 2 3 4

5 di tri tetra penta 7 8 9 10 hepta

octa nona deca 4) Name the 2nd non-metal and change its ending to -ide 5) Add a prefix to indicate how many Problems Write the name of the following compounds: carbon monoxide 1) CO 2) NI3

3) N2O 4) SF6 nitrogen triiodide dinitrogen monoxide sulfur hexaflouride diboron trioxide 5) B2O3 Write the formula for the following compounds: 6) Phosphorous Pentachloride

PCl5 7) Nitrogen Monoxide NO 8) Dinitrogen Tetroxide 9) Tetraphosphorous Decoxide N2O4 P4O10 Problems

1) KCl 2) Na2S 3) H2O 4) SO2 5) K3PO4 6) FeCl3 7) (NH4)2SO4 8) SCl2 9) Cu(OH)2 10) P2O5 Potassium chloride Sodium sulfide

Dihydrogen monoxide Sulfur dioxide Potassium phosphate Iron(III) chloride Ammonium sulfate Sulfur dichloride Copper(II) hydroxide Copper(II) hydroxide 8) Sodium Iodide NaI

9) Aluminum Sulfate Al2(SO4) 10) Phosphorous Pentabromide PBr5 11) Magnesium Nitride Mg3N2

Naming Acids Acids that do not contain oxygen 1) Begin the name with

hydro 2) Name the anion, but change the ending to -ic 3) Add acid on the end HCl = hydrochloric acid HF = hydrofluoric acid EXCEPTION, if in the gas phase, treat like a regular covalent compound for naming with no prefixes HCl(g) = hydrogen chloride

Acids that contain oxygen/oxyanions 1) Do not put hydro at the beginning 2) Begin the name with the anion 3) If the anion has the ending -ate, change this to -ic acid 4) If the anion has the ending -ite, change this to -ous acid HClO4 perchloric acid HClO3 chloric acid

HClO2 chlorous acid HClO hypochlorous acid Problems Name the following 1) 2) 3) 4) 5) 6)

7) 8) 9) 10) HBr(g) HBr(aq) HNO2(aq) HNO3(aq) HI (aq) HI (g) H2CO3 (aq) H3PO4 (aq)

H3PO3 (aq) HCN (aq) Hydrogen bromide Hydrobromic acid Nitrous acid Nitric acid Hydroiodic acid Hydrogen iodide Carbonic acid Phosphoric acid Phosphorous acid hydrocyanic acid

Molecular Structures Ball & Stick Models Water H2O Methane CH4 Space-Filling Models

Octet Rule or Duet or H-H Making Lewis Dot Structures 1) 2)

Count the total number of valence electrons in the molecule. Ex: PCl3 Use atomic symbols to draw a proposed structure with shared pairs of electrons Pick a central atom atom that wants to make the most bonds Atoms dont tend to bond to other atoms of the same element when they can avoid it Exception: Carbon

3) Place lone pair electrons around each outside atom (except H) to satisfy the octet rule, beginning with the terminal atoms 4) Place any leftover electrons on the central atom 5) If the number of electrons around the central atom is less than 8, change single bonds to the central atom to multiple bonds (double or triple). 6) Ex: CH2O Atom Covalence chart

Covalence Non number bonding electrons H C or Si P or N O or S F, Cl, Br, or I

1 4 3 2 1 0 0 1 2 3 B

3 0 What Certain Atoms Like To Do Halogens Like to have one single bond and 3 lone pairs (non-bonding electrons) F,Cl, Br, I Cl Cl C Cl

Cl Carbon Likes to have 4 single bonds and no lone pairs A double bond counts as two singles A triple bond counts as three singles Likes to be central Cl Cl Cl Likes to bond to other carbons Cl C C C C C Cl

Cl Silicon Likes to do what carbon does Cl Cl Si Cl Cl Oxygen Likes to have two single bonds and 2 lone pairs H O H

Sulfur Likes to do what oxygen does May expand its octet H S H Nitrogen Likes to have 3 single bonds and one lone pair H H N C C H H N H H

O O S O H O H Phosphorous Likes to do what nitrogen does May expand its octet H H P H H O H

H C P C H H H C H H H Hydrogen Likes to be terminal with only one single bond H No lone pairs! N C C H H

Boron Likes 3 bonds and no lone pairs (sextet) H H B H Draw the LDSs for the following molecules: 1)Cl2O Problems 2)C2H4

3)C2H6O Problems Draw the Lewis Structures for the following molecules: 1) SH2 2) C3H8 3)

5) CH3OH 6) C2H2 Si2H6 7) BF3 9)

N2 H4 10) CH2OS 11) C2H6O 12) P4 Dot structures for ions Polyatomic ions contain covalent bonds Covalent chart can be violated, but the octet rules is not

Comparing current e-s to expected valence e-s can tell you charge of an atom One less e- = positive charge One more e- = negative charge Resonance Two or more electron arrangements are possible for the same arrangement of atoms The structures differ

in only the multiple bond and lone pair placement Resonance meaning The true structure is an average of all resonance structures Resonance allows electros to move (spread) across multiple atoms, this stabilizes the molecule as a whole

Spread out electrons aka delocalized electrons Practice with resonance O3 N2O Electronegativity The measure of the

ability of an atom to attract electrons to itself Increases across period (left to right) and Decreases down group (top to bottom) fluorine is the most electronegative element

francium is the least electronegative element Electronegativity Scale Types of Bonding 1) Non-Polar Covalent Bond:

Difference in electronegativity values of atoms is 0.0 0.4 Electrons in molecule are equally shared Examples: Cl2, H2, CH4 ENCl = 3.0 3.0 - 3.0 = 0 Pure Covalent 2) Polar Covalent Bond:

Difference in electronegativity values of atoms is 0.4 2.0 Electrons in the molecule are not equally shared

The atom with the higher EN value pulls the electron cloud towards itself Partial charges Examples: HCl, ClF, NO ENCl = 3.0 ENH = 2.1 3.0 2.1 = 0.9 Polar Covalent 3) Ionic Bond:

Difference in EN above 2.0 Complete transfer of electron(s) Whole charges ENCl = 3.0 ENNa = 1.0 3.0 0.9 = 2.1

Ionic Problems Draw the lewis dot structure then predict the type of bonding in the following compounds using differences in EN values of the atoms. Indicate the direction of the dipole moment if applicable 1) KBr

2) HF 3) BrI 4) O2 Valence Shell Electron Pair

Repulsion Theory VSEPR theory: Electrons repel each other Electrons groups in a molecule arrange themselves so as to be as far apart as possible Minimize repulsion Determines molecular geometry Defining Molecular Shape Electron pair geometry: the geometrical

arrangement of electron groups around a central atom Atoms and lone pairs count as electron groups Molecular Geometry: the geometrical arrangement of atoms around a central atom Ignore lone pair electrons 2 e- groups surrounding the central atom e- pair geometry: linear MG: linear

AXE designation: AX2E0 A: Central Atom X: Bonding pairs E: Non-bonding pairs Example: BeCl2, CO2 O C O 3 e- groups 3 Bonds, 0 Lone Pairs e- PG: Trigonal Planar

(Triangular planar) MG: Trigonal Planar AX3E0 BF3 2 Bonds, 1 Lone Pair e- PG: Trigonal Planar (Triangular planar) MG: Bent/angular AX2E1 GeCl2

4 e groups - 4 bonds, 0 Lone Pairs e- PG: Tetrahedral MG: Tetrahedral AX4E0 CH4 3 bonds, 1 Lone Pair e- PG: Tetrahedral

MG: Triangular Pyramidal AX3E1 NH3 2 bonds, 2 Lone Pairs e- PG: Tetrahedral MG: Bent/Angular AX2E2 H2O Molecular Polarity

Drawing LDS With Correct Geometry Commonly seen for tetrahedral geometry Problems Draw the 3D Lewis Dot Structures, using wedges and dashes when applicable, for the following molecules and then identify the net dipole, if any. 1) BF3 2)

CH2O 3) CBr4 4) CHCl3 Chapter 4 checklist Covalent compounds- what is a covalent compound?

Know the rules for naming. Lewis dot structures how to draw molecules Electronegativity What is it and how does it determine the type of bond? Pure covalent, covalent, and ionic bonds depend on the electronegativity difference between the each atom in question Valence shell electron pair repulsion theory Resonance Molecular Geometry and molecular polarity

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