IB Chemistry HL Notes according to official criteria/checkpoints. IB Chemistry. Year 2016 Mark 7.00 Pages 58 Published Jan 11, 2017

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1 IB Chemistry Year 2016 Mark 7.00 Pages 58 Published Jan 11, 2017 IB Chemistry HL Notes according to official criteria/checkpoints By Anya (99.95 ATAR)

2 Powered by TCPDF ( Your notes author, Anya. Anya achieved an ATAR of in 2016 while attending Presbyterian Ladies' College Currently studying Commerce (Chancellor's Scholars Program) at University of Melbourne Anya says: I have been doing the IB Diploma program for the past 2 years, and finished it in I received a perfect IB score of 45 (ATAR equivalent of 99.95) by receiving perfect 7s in higher level chemistry, history, economics, and standard level maths, english and french b. Much of this success can definitely be attributed to my comprehensive yet succinct notes and the way in which they address and were made according to the IB criteria obtained from the IB study guides. These notes are compiled from a number of different course companions, study guides, online resources and school notes

3 Topic 4: Chemical bonding and structure 4.1 Ionic bonding and structure Deduction of the formula and name of an ionic compound from its component ions, including polyatomic ions. Naming ionic compounds: The metal is named first. The non-metal s ending changes to ide E.g. Sodium + chlorine = Sodium Chloride Polyatomic ions: Explanation of the physical properties of ionic compounds (volatility, electrical conductivity and solubility) in terms of their structure. Volatility Non-volatile: The forces of electrostatic attraction in their lattice structure is so strong that they take large amounts of heat to melt and don t vaporise easily Electrical conductivity As a solid they don t conduct: Ions aren t free to move so they can t carry a charge In a liquid or aqueous state: If they can dissolve or are melted to molten, the charged ions can move and conduct electricity Solubility Generally soluble in ionic or polar solvents (e.g. water) Not soluble in non-polar solvents This is because polar solvents can pull apart the charged ions in their structure and disperse them through the solvent to form a solution

4 4.2 Covalent bonding Deduction of the polar nature of a covalent bond from electronegativity values. Non polar When two elements covalently bond, if they are the same element, there is no electronegativity difference and they re non polar. The only intermolecular attraction they have is weak dispersion forces Polar If the elements are different there s an electronegativity difference. The one with higher electronegativity gets a partial negative charge and the other gets a partial positive charge. Polar molecules can have 2 or 3 different intermolecular attractions: Dispersion forces AND Dipole-dipole OR H-FON 4.3 Covalent structures What does the min. electronegativity difference have to be so the molecule is classified as polar? Is it 1.8? Deduction of Lewis (electron dot) structure of molecules and ions showing all valence electrons for up to four electron pairs on each atom. It shows the valence (outer shell) electrons 1) There are four electron places that fit two electrons each 2) You put one electron in each first 3) If the four electron places are filled, you then add an electron to the electron that s already there since electrons like being in twos Types of Domains 1) Lone pair/non-bonding pair: There are two electrons in the doman 2) Bonding pair: There is one electron that likes being in twos and can bond with other electrons in other atoms The use of VSEPR theory to predict the electron domain geometry and the molecular geometry for species with two, three and four electron domains. 2 electron domains (Domain geometry = linear) Linear and electron domains (Domain geometry = Trigonal planar) 1) No lone pairs: Trigonal planar and 120 2) 1 lone pair: Bent and electron domains (Domain geometry = tetrahedral) 1) No lone pairs: Tetrahedral and ) 1 lone pair: Trigonal pyramidal and 107 2) 2 lone pair: Bent and electron domains (Domain geometry = triangular bipyramidal) 1) No lone pairs: Triangular bipyramidal 90, 120 (sticking out), 180 2) 1 lone pair: See-saw/unsymmetrical tetrahedron 90, 117 3) 2 lone pairs: T-shaped 90 4) 3 lone pairs: Linear 180 (NON-POLAR) 6 electron domains (Domain geometry = octahedral) 1) No lone pairs: Octahedral 90 2) 1 lone pair: Square pyramidal ) 2 lone pairs: Square planar 180 (NON POLAR) 4) 3 lone pairs: Trigonal pyramidal 5) 4 lone pairs: Linear

5 Prediction of bond angles from molecular geometry and presence of nonbonding pairs of electrons. Refer above Prediction of molecular polarity from bond polarity and molecular geometry. If the atoms in the bond have different electronegativity values AND their shape is not symmetrical so the charges balance out, the molecule is polar Shapes and Symmetry Linear, trigonal planar and tetrahedral molecules are symmetrical and nonpolar if the charges balance out Bent molecule and trigonal pyramidal molecules are always polar even if the elements are the same e.g. ozone (O3) Deduction of resonance structures, examples include but are not limited to C6H6, CO3 2- and O3. Explanation of the properties of giant covalent compounds in terms of their structures. Diamond: 1) Non-conductor of electricity (els aren t mobile) 2) Very efficient thermal conductor better than metals (If you push an atom, has an effect on the atoms bonded to it) and insulator (no els mobile) 3) Highly transparent lustrous crystal, 4) Very high melting point (strong covalent bond in all 3 dimensions) 5) Insoluble (weak dispersion forces between carbon and water compared to carbon to carbon) 6) Hard (strong covalent bonds hold structure) and brittle (bonds are directional) Graphite: 1) Good electrical conductor: (One non-bonded delocalised electron) 2) Not good thermal conductor: But it can conduct across the layers but between there are only weak disp. Forces and the electrons can t carry heat 3) High MP: Strong covalent bonding within layers 4) Non-lustrous grey crystalline, soft/slippery (because of layers) 5) Most stable carbon allotrope 6) Brittle (Bonds are directional) and hard (strong covalent bonds) 7) Insoluble (Same for diamond)

6 Powered by TCPDF ( C 60 buckminsterfullerene: 1) Semiconductor of electricity (accepts els to form negative ions) 2) Very low thermal conductivity 3) Yellow crystalline solid, soluble in benzene, light, strong, 4) Soft and slippery (weak disp. between some molecules) 5) Low melting point (only dispersion forces have to be melted) 6) Brittle (Soft weak crystals) 7) Electrical insulator (nano-tubes conduct) 8) Soluble in water Graphene 6) Insoluble in water 1) Very good electrical conductor (one delocalised electron) 2) Best thermal conductor () 3) Almost completely transparent 4) Very flexible (flat like paper) 5) Strong (Covalent bonds) Very high melting point (strong covalent bonds) 1) High melting point (strong covalent bonds) 2) Very hard (strong covalent bonds) 3) Non-conductor of electricity (no mobile electrons) 4.4 Intermolecular forces Deduction of the types of intermolecular force present in substances, based on their structure and chemical formula. Dispersion forces: All covalent molecules including non-polar molecules have this Dipole-dipole forces: Polar molecules have this and some have a special dipole-dipole (below) H-FON: When a molecule containing H is covalently bonded to fluorine, oxygen or nitrogen and another molecule s FON bonds to H or H bonds to the FON intermollecularly. Note: When asked to name the intermolecular forces present in a substance, name ALL of them, including dispersion forces even if they have H-FON as well