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21 Cards in this Set
- Front
- Back
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How does ionic bonding occur? |
Between a metal and non metal. Electron (s) from 1 atom go to another. Become cation and anion and electrostatic attraction keeps them together. |
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What are the properties of ionic structures |
Ionic crystals are giant lattices - high boiling point Soluble in water Can't conduct as a solid, can when molten. |
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How does metallic bonding occur? |
Outer shell electrons of metal atoms are delocalised. Metal atoms - [ions]+ and a sea of delocalised electrons |
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What are the properties of metals?
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Ductile + Malleable - no bonds holding ions together Good thermal and electrical conductors Insoluble because of strong bonds Higher no. of delocalised electrons = higher the m.p |
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How does covalent bonding occur? What are the 2 types? |
Between 2 non-metals and electrons are shared. Simple covalent molecules. Macromolecular (giant covalent structure). |
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How are simple covalent compounds formed? What are the properties? |
Atoms in molecule held together by strong covalent bonds. Molecules held together by weaker Intermolecular forces. Low b.p - van der waal forces easily overcome Poor solubility in water No conductivity - no free electrons |
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What are macromolecular structures? |
Type of crystal structure. Carbon atoms can form it has it can form 4 strong, covalent bonds |
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What is graphite? |
Sheets of flat hexagons covalently bonded with 3 bonds each. Sheets bonded together by weak van der Waal forces 4th outer electron is delocalised.
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What properties does graphite have? |
Weak van der Waal forces - sheets slide over each other - dry lubricant & pencils
Delocalised electrons - conduct electricity
Low density - sports equipment
Bonds in hexagon sheets - high m.p (3900k+)
Insoluble - bonds in sheets too strong |
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What is diamond? |
Crystal lattice structure. Each C atom covalently bonded to 4 other C atoms. |
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What are the properties of diamond? |
Extremely hard - drills/saws Cant conduct electricity Good thermal conductor - vibrations can travel through Very high m.p (3800k+) Insoluble |
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What are dative covalent bonds? |
One atom provides both of the shares electrons. E.g. NH3 has a lone pair, can donate it to a hydrogen atom to form NH4+ |
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Define: Charge Cloud |
An area where there's a high chance of finding electrons (as they don't stay still) |
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Define: Electronegativity |
The ability to attract the bonding electrons in a covalent bond. Measured on Pauling Scale F is most electronegative Every element to the left is 0.5 less |
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Define: non-polar |
Equal electronegativity between 2 atoms (e.g diatomic gases). Equally attracted to the nuclei. |
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Define: polar |
Difference in electronegativity caused by shift in electron density. (Delta+, Delta-) Causes a dipole |
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What are Polar Molecules? |
When the charge is distributed unevenly over a whole molecule, causing a permanent dipole. E.g. HCl has uneven charge = polar molecule CO2 symmetrical = dipoles cancel = no permanent dipole = non-polar |
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What are (permanent) dipole-dipole intermolecular forces? |
Weak electrostatic forces between delta+ and delta- |
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What are hydrogen intermolecular forces? |
Hydrogen bonding with electron pair of F, N, O Strongest |
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What are van der Waal intermolecular forces? |
Electrons in charge clouds move rapidly and likely to be on 1 side (temporal dipole) Weakest forces |
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How is Valences shell electron pair replusion theory used for shapes of molecules? |
1) find central atom & electrons in outer shell 2) add electron for each atom bonded to central atom 3) if a positive ion: minus electron 4) add up all electrons. Divide by 2 (to give electron pairs) 5) compare electron pairs to bonded pairs and lone pairs |
