Ch. 12 Notes---Covalent Bonds ____________ electrons between two atoms in order to fill the outer energy level (or shell) Each bond involves the sharing of _____ _________ of electrons. Single Bonds= __ e-’s Double Bonds= __ e-’s Triple Bonds=__ e-’s Sharing one pair 2 4 6 Sharing Sharing is Caring!! Caring is Covalent!!!

Ways to Represent Covalent Bonds in Compounds Quantum Mechanical or Bohr Model of the Atom.

Ways to Represent Covalent Bonds in Compounds Quantum Mechanical or Bohr Model of the Atom.

Ways to Represent Covalent Bonds in Compounds (2) “Dots” for bonds. (Lewis Structures) a) H2 H · + · H  b) F2 :F· + ·F:  c) N2 :N · + ·N:  (triple bond) d) NH3 H:H .. .. .. .. :F:F: .. .. .. .. · · · · :N::N: · · .. H:N:H .. H

Ways to Represent Covalent Bonds in Compounds (3) “Lines” for bonds. a) H2 b) F2 c) N2 d) NH3 e) H2O H–H .. .. :F–F: .. .. :N≡N: ¨ H–N–H ׀ H .. H–O: ׀ H

Carbon’s Hybrid Orbital C …___ ___ ___ ___ (Before) 2s 2p ↑ ↓ ↑ ↑ C …___ ___ ___ ___ (After: 4 covalent bonds available) ↑ ↓ ↑ ↑ ↑ 2sp3 Practice Problem: Draw CH4 using arrows, dots, and lines for bonds. C …___ ___ ___ ___ ↑ ↑ ↑ ↑ 2sp3 H ___ 1s ↑ H ___ 1s ↑ H ___ 1s ↑ H ___ 1s ↑

“HONClBrIF” The 7 Diatomic Elements Some elements will covalently bond to themselves to form a molecule composed of ____ atoms. These elements are never found in nature as single atoms. Instead, they will be bonded as a ________ when they are in the “_________________” state. The 7 diatomic elements are the gases H, O, N, and all of the _________________, (Group 7A). H2, O2, N2, Cl2, Br2, I2, F2 “HONClBrIF” two pair elemental halogens

Air contains N2 and O2 molecules.

The decomposition of two water molecules

PCl5 (___ e-) SF6 (___ e-) BF3(___e-) Octet Rule Atoms want ___ e-’s in their outer shell when forming compounds. This will mean ___ dots around them all together. This is the stable e- configuration of a __________ _______! Important exception: Hydrogen = only needs __ to be full (like He). Other Exceptions: PCl5 (___ e-) SF6 (___ e-) BF3(___e-) 8 8 noble gas 2 10 12 6

VSEPR Theory: Molecular Shapes Most shapes are based on a __________________. Examples: CH4 CCl4 Removing the top of the tetrahedral makes the ________________ shape. Examples: NH3 PCl3 tetrahedral pyramidal

VSEPR Theory: Molecular Shapes Removing one side of the pyramid makes the _____________ shape. Examples: H2O H2S If there are only two atoms bonded, it is ______________. Examples: O2 HCl CO2 (linear because of its double bonds.) bent linear

VSEPR Theory: Molecular Shapes Another we will need to know is called “trigonal planar”. “Trigonal” means that the central atom is bonded to ___ other atoms. “Planar” means that the 3 atoms all lie in the same ______________. Example: BF3 (Notice that Boron will only have ___ e-’s around it. The missing pair of electrons will make it planar instead of ________________.) 3 plane 6 pyramidal

Polar and Nonpolar Bonds Even though the electrons in a covalent bond are shared, sometimes the attraction for the bonded pair, (the _____________________), is uneven. This gives rise to 3 bond types. nonpolar covalent bonds: ____________ sharing of the e- pair polar covalent bonds: ________________ sharing of the e- pair ionic bonds: a ___________ of e-’s from the metal to the nonmetal How To Determine the Bond Type Bond type is based on the electronegativity _____________ between the two bonded atoms. electronegativity equal unequal transfer difference

Figure 12.4 The three possible types of bonds. nonpolar polar ionic

Figure 12.4: Electronegativity values for selected elements.

How To Determine the Bond Type 0 to 0.4 = ______________ covalent bond 0.5 to 2.0 = _____________ covalent bond Above 2.0 = _______________ bond Practice Problems: Determine the type of bond that forms between the atoms in the following compounds. a) CO2 b) NaCl c) CH4 nonpolar polar ionic 2.5 3.5 0.9 3.0 2.5 2.1 1.0 = polar covalent 2.1 = ionic 0.4 = nonpolar covalent

Polarity of Molecules One side is slightly (__) and the other side is slightly (__). Polar molecules are also known as _______________. Polarity depends on the __________ and symmetry of the molecule. symmetrical molecules (looks the same on all sides)= ___________ asymmetrical molecules = ___________ Polar molecules are moved by ____________ charges. (DEMO!) + – dipole shape nonpolar polar static

a) CH4 b) NH3 c) H2O d) HCl e) BF3 Molecular Polarity Practice Problems: Determine if the following molecules are polar or nonpolar based on their shape. a) CH4 b) NH3 c) H2O d) HCl e) BF3 symmetrical tetrahedral asymmetrical pyramid asymmetrical bent asymmetrical linear symmetrical trigonal planar nonpolar polar polar polar nonpolar Dipole of NH3 Dipole of H2O

Bond Dissociation Energy This is the energy needed to ___________ the bond. Generally, the longer the bond, the _____ energy it takes to break it. Single bonds take ________ energy to break than double bonds and triple bonds require the _________ energy to break. When bonds form, energy is _____________. (Breaking bonds requires the addition of energy.) break less less most released

Bond Dissociation Energy

Intermolecular Attractions The __________ attractions between one molecule and another are called _______ ______ ________ forces. They cause gas particles to stick together and _______________ at low temperatures. weak Van der Waals condense

Dispersion Forces There are two types of intermolecular forces: (1) ____________________ forces: (the weaker type) caused by random _______________ motion generally _____________ with ________ electrons in the molecule Dispersion electron stronger more − exist between all types of molecules − This force causes Br2 to be a liquid and I2 to be a solid at room temperature.

Dipole Interaction Forces (2) ____________ interactions: (the stronger force) caused by the attraction of the (__) side of one polar molecule and the (__) side of a different polar molecule Dipole + –

Hydrogen Bonds ________________ “Bonds” are a special type of dipole interaction. This attraction between molecules is not a chemical bond. Electrons are not being shared or transferred. They occur between the hydrogen of one polar molecule and the ____, ___ or ___ of another polar molecule. Hydrogen N O F Hydrogen Bonding in Water

Hydrogen Bonds The ladder rungs in a DNA molecule are hydrogen bonds between the base pairs, (AT and GC).

Hydrogen Bonds in DNA

Intermolecular Forces At Work Substances that contain stong intermolecular forces have a ________ melting point and a _________ boiling point. Liqids containing strong intermolecular forces have higher surface tension and a higher viscosity. higher higher

Surface Tension

Ionic Bonding & Ionic Compounds Ionic Bonds Form when ___________ transfer their _____________ electrons to a _______________. The forces of attraction between the ____________ (+) and the _____________ (-) bind the compound together. How to Represent an Ionic Bond Electron Configuration: Na 1s2 2s2 2p6 3s1 Cl 1s2 2s2 2p6 3s2 3p5 metals valence nonmetal cation anion Na… ___ 3s ↑ Cl… ___ ___ ___ ___ 3s 3p ↑ ↓ ↑ ↓ ↑ ↓ ↓

How to Represent an Ionic Bond 2) Bohr Model Lithium Fluorine

How to Represent an Ionic Bond 3) Electron Dot Notations: Na + Cl  [ ] [ ] Practice Problems: (1) Draw the electron dot notation for the formation of an ionic compound between sodium and oxygen. (2) Draw the electron configuration notation for the formation of an ionic compound between magnesium and fluorine. Na+1 Cl -1

S [ S -2] K [K+1] Practice Problems: 3) a) Draw the electron dot notation for a potassium atom. b) Draw the electron dot notation for a potassium ion. (4) a) Draw the electron dot notation for a sulfur atom. b) Draw the electron dot notation for a sulfur ion. K [K+1] S [ S -2]

Properties of Ionic Compounds and Covalent Molecules _______________ of electricity when dissolved water or melted. formed between __________ and _________________ have _________ melting points usually ________ soluble in water form ___________________ solids Conductors metals nonmetals high (dissolved salt) very ionic crystalline

Crystalline Patterns

Pyrite mineral form of the iron disulfide (FeS2) with a gold-like appearance, making it also known as "fool's gold"

Gypsum Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O.

Properties of Ionic Compounds and Covalent Molecules Molecular: ________________ of electricity formed between two _______________ usually have ________ melting points solubility in water _______: (polar =dissolve; nonpolar = insoluble) forms ______________________solids. For a compound to to conduct electricity it must have: (1) Charged Particles (________) (2) Particles Free to Move (___________ or __________ phase) Insulators nonmetals low varies covalent crystalline ions liquid aqueous

Quartz Quartz is the common mineral form of silicon dioxide (SiO2). It is the dominant mineral in most sands and sandstones.

Demonstration PureH2O great conductor good conductor poor conductor nonconductor