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Bonding - SCH3U
Molecular Bonding Unit
Name | Related Information |
---|---|
Drawing Lewis Structures | 1)Write element symbol 2) Drow one dot for each valence electron 3) Dots are spread over the four sides |
Determining the Number of Valence Electrons | The number of valence electrons is equal to the group number with the exception of helium |
Representation of Ionic compounds | |
Covalent bonding | H-Cl (Cl would have 3 lone pairs) |
Structural Formula | H-Cl (No lone pairs are shown) |
Double and Triple bonds | Atoms can share 4 electrons for a double bond, or 6 electrons for a triple bond (ig. O=O , however each O would have 3 lone pairs) |
Bonding Capacity | The number of shared electron pairs, with covalent bonds, that an atom can form |
Drawing Lewis Structures (First 3 steps) | 1) Arrange the element symbols so the the element with the highest bonding capacity is the central atom. 2) Add up the number of valence electrons (ass 1 for each negative charge, and subtract on for each positive charge) 3) Draw a skeletal structure |
Drawing Lewis Structures (Last 3 steps) | 4) Complete the octets and peripheral atoms (Hydrogen won't have lone pairs) 5) Place extra electrons on the central atom 6) If the central atom doesn't have an octet, try forming multiple bonds by moving lone pairs |
Co-ordinate Bovalent Bonds | Both electrons are donated by the same atom |
VSEPR Accronym | Valence Shell Electron Pair Repulsion Thory |
Covalent Bond Characteristics | Highly directions, a molecule of a substance, and has a definite shape |
Why can we Predict Covalent Bond Shapes | We assume that the lone electron pairs in the valence shell of atoms stay as far apart as possible |
VSEPR Formula: AX | Name of Shape: Linear |
VSEPR Formula: AX2 | Name of Shape: Linear |
VSEPR Formula: AX3 | Name of Shape: Trigonal Planer |
VSEPR Formula: AX4 | Name of Shape: Tetrahedral |
VSEPR Formula: AX3E | Name of Shape: Trigonal Pyramidal |
VSEPR Formula: AX2E2 | Name of Shape: Bent |
Intramolecular Force | Attractive forces between atoms and ions within a molecule |
Intermolecular Forces | Attractive forces between molecules (ig. Vander Walls forces) Weaker that intramolecular forces |
Proof of Intermolecular Forces | If covalent bonds were the only forces at work, most molecular compounds would be gasses as the attraction would not be strong enough to group them as liquids or solid |
Dipole - Dipole attraction | Force of attraction between oppositely charges ends of polar molecules. Quantitative measure of the charge separation in a bond. |
Dipole - Dipole arrows | Electronegativities are used to determine the direction of the dipole moment, the arrow will point towards the more electronegative element |
London Dispersion | Attractive forces between all molecules, including non polar ones. Result of temporary displacement of electron cloud around atoms, temporary short lived dipoles, weaker than dipole - dipole |
Hydrogen Bonding | Strong dipole-dipole force between the positive hydrogen atom of one molecule and the highly electronegative atom of another molecule. (H w/ F,O or N created hydrogen bonding due to strong electronegativity) |
Non-Polar Covalent Bonds | 2 identical atoms, or atoms with similar electronegativities. Electronegativity difference must be between 0.4 |
Polar Covalent Bonds | If electronegativities are unequal. the electrons spend more time with the more electronegative bond |
Polar molecules | Not all molecules with polar bonds are polar molecules A molecule can have polar bonds but be non polar if the molecular symmetry causes the dipoles to cancel eachother Totally symmetrical atoms are non polar |
Heteronuclear diatomic molecules | These molecules have two different atoms and is polar |
Molecular Properties of Polar Compounds | Significant intermolecular attraction (Hydrogen bonding and dipole-dipole) Higher melting and boiling points Dissolve in polar compounds but not non polar |
Molecular Properties of Non-Polar Compounds | Small intermolecular attraction (London forces) lower melting and boiling points Dissolve in non polar compounds but not polar |
Electronegativity Differeces | Non polar covalent (0-0.4) Polar covalent (0.41-1.66) Ionic (1.67 or greater) |