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26 Cards in this Set
- Front
- Back
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What are the terms bond length and bond angle?
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Bond length - Distance between the nuclei of 2 bonded atoms
Bond angle - Angle between two covalent bonds |
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What is the bond angle of a tetrahedral?
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107.5 degrees
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What is the electron pair repulsion theory?
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Lone Pair - Lone Pair repels more then Lone Pair - Bond Pair repels more than Bond Pair - Bond Pair.
LP-LP > LP-BP > BP-BP |
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How many lone pairs and bond pairs are in a pyramidal shaped molecule?
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3 Bond Pairs
1 Lone Pairs e.g. NH3 |
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What is the name given to this term?
'Different forms of the same element in the same physical state' |
Allotropes
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What makes Diamond different to Graphite? (3 differences)
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1.The Carbon in Diamond has 4 bonded electrons where as in Graphite it has 3 bonded electrons.
2.Due to the bonding Diamond doesn't conduct electricity where as Graphite does. 3.Graphite has weak intermolecular forces between layers where as Diamond doesn't due it's rigid structure. |
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What is electronegativity?
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a measure of the tendency of a atom a covalent bond to attract other bonding electrons
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Why does electro-negativity increase along a period?
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Atomic radius decreases so outer electrons are more attracted to the nucleus.
No. of protons in nucleus increases so greater puller on electrons. |
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Why does electro-negativity decrease down a group?
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Atomic radius increases so outer electrons are far away from the nucleus therefore less attracted
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What character will a molecule resemble when the electro-negative difference is large and when the difference is small?
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Large electronegative difference = Ionic character
Small electro-negative difference = Covalent character |
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When do polar bonds exist?
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When there's a difference in electro-negativity between 2 atoms
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What does a positive and negative dipoles indicate about electro-negativity in a molecule?
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Positive dipole - atom is slightly positive
Negative dipole - atom is slightly negative Electro-negativity - Negative dipole > Positive dipole |
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Why do noble gases have on electro-negative value?
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They have full outer shells therefore wouldn't have a tendency to attract other atoms
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What properties do polar molecules share?
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1.Different bonds
2.Identical bonds and lone electron pairs on central atom 3.Asymmetrical |
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What do non-polar molecules share?
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1.Symmetrical
2.Same bonds 3.No lone pairs |
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What does the term intramolecular mean?
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Bonding within a molecule e.g. ionic, covalent bonding
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What does the term intermolecular mean?
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Forces of attraction between molecules, they determine melting and boiling points. e.g. London forces and hydrogen bonds
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What are the 3 main intermolecular forces?
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1.Hydrogen bonds (strongest)
2.Permanent dipole-dipole attraction 3.London forces (weakest) |
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What are London forces also known as?
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Van Der Waals forces
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What are London forces?
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Intermolecular forces that exist between molecules. They arise from temporary attraction between neighbouring dipoles.
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Which of the 3 main intermolecular forces is the strongest?
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Hydrogen bonds
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Why is ice less dense than water?
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The hydrogen bonds in solid ice holds the molecules further apart than in a liquid
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What type of bond holds the double-helix in DNA (deoxyribonucleic)?
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Hydrogen bonds between base pairs
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What property does a substance have if it can form hydrogen bonds with water?
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Becomes more soluble e.g. ethanol
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What bond does HF form (hydrides)?
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Hydrogen bonds
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What bond develops when a molecule has many electrons?
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Strong London forces
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