U1C2,3 Flashcards
what is the structure of ionic compounds
There are many ionic bonds in a compound arranged as a giant lattice structure
what are the properties of ionic compounds
Composed of metal and non metal
Hard, brittle, high melting point, conduct electricity if melted or dissolved
what is a formula unit
A formula unit is the smallest repeating unit in an ionic crystal
define molecular elements and compounds
Two or more non-metals (typically)
properties of molecular compounds
can be solid, liquid or gas, Solids can be soft, waxy, flexible or crystalline, Low melting/boiling points, Poor electrical conductivity when dissolved in water or melted
Molecular compounds form molecules
How do you find formal charge? What should never occur in a molecular compound?
Formal Charge = Valence Electrons - Lone Pair Electrons - Bonded Electrons/2
A negative ion should never be bonded with a positive one
What is AXE? What does each letter mean?
A - Central Atom
X - The Bonds Formed To The Central Atom
E - The Amount of Lone Pairs the Central Atom Has
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What are the 3 common VSEPR shape names? What are the 2 modification? How are they all formed?
What are their angles?
Linear - Two Surrounding Atoms, No Lone Pairs (Also For 2 Atoms Bonded) 180 degrees
Trigonal Planar - Three Surrounding Atoms, No Lone Pairs. 120 degrees
Tetrahedral - 4 Surrounding Atoms, No Lone Pairs. 109.5 degrees.
Trigonal Pyramidal - 3 Surrounding Atoms, Lone Pairs. <109.5 degrees.
Bent/Angular - 2 Surrounding Atoms, Lone Pairs. «109.5 degrees.
What is electronegativity?
Electronegativity is a unit less form of measurement that represents the amount of attraction electrons have towards an element in a bond.
How do you determine the Polarity of a bond? What does each Polarity represent?
Bond Polarity = Higher EN Atom - Lower EN Atom
Non-polar - <0.5 Electronegativity
Polar - 0.5-1.7 Electronegativity
Ionic - 1.7+ Electronegativity
How are bond and molecule dipoles drawn?
Bond dipoles are drawn as such -+—-> and point to the more electronegative element on each bond. A molecule dipole is drawn the same way and points to the direction where the more electronegativity is. Dipoles are not present on non-polar molecules.
How can you tell if a molecule is polar
Molecular polarity depends on the polarity of the bonds within the molecule and on the shape of the molecule.
- A diatomic molecule will be polar if the covalent bond is polar and non-polar if the bond is non-polar.
- A polyatomic molecule with only non-polar covalent bonds will be non-polar.
- A polyatomic molecule with several polar covalent bonds will be polar if the molecule is asymmetrical and non-polar if the molecule is symmetrical.
- Molecular diagrams and models help us to visualize whether a molecule is symmetrical or asymmetrical.
Define intra and intermolecular bonds
An intramolecular force is a force that binds the atoms in a molecule together.
An intermolecular force is a force that binds separate molecules together.
What are the 3 forms of intermolecular bonding from weakest to strongest? How does each form/work? Which molecules does each apply to?
London Dispersion Forces - Attractions caused by temporary shifts in the electron cloud. Very weak. Applies to every molecule, always.
Dipole-Dipole Forces - Attractions caused by the intermolecular force between oppositely charged ends of polar molecules. Dipoles will always rotate to face the opposite ends to stick together. Applies to most polar molecules.
Hydrogen Bonding - A very strong dipole-dipole force. Each molecule consists of a hydrogen atom covalently bonded to an atom of nitrogen, oxygen, or fluorine.
Describe the special properties of water and the role of hydrogen bonds.
Water has unusually high melting and boiling points. This is because of the molecules bent shape and it’s hydrogen bonds, making it particularly strong and polar.
