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Description
Flashcards by Talya Hambling, updated more than 1 year ago
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Created by Talya Hambling
about 9 years ago
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| Question | Answer |
| definition of ionic bonding | strong electrostatic force of attraction between charged molecules, due to transfer of electrons |
| how does ionic radius have an affect on bond strength | smaller ones can pack closer together so will have a stronger attraction |
| how does ionic charge have an affect on bond strength | greater charge means stronger bonds, so higher melting and boiling points too |
| what are ionic radii trends down a group, and why | they get bigger, since there is a higher atomic number and there are more electron shells |
| how do physical properties provide evidence for ionic bonding | -high melting points due to strong attraction -soluble in water but not in non polar substances, since they're charged -only conduct electricity when molten or liquid -they're brittle and cant be shaped |
| how does migration of ions provide evidence for ionic bonding | electrolysing ionic compounds give different colours at the anode and cathode, showing that one is negative and the other positive (they are charged) |
| what is a cathode/anode | cathode = negative stick anode = positive stick |
| definition of a covalent bond | strong electrostatic force of attraction between two nuclei and the shared pair of electrons between them |
| what is a dative bond | a covalent bond where both electrons come from one atom |
| what is bond length | distance between the two nuclei in a covalent compound. this is where the attractive (toward the electrons) and repulsive (from each other) forces balance out |
| how does electron density affect bond length and enthalpy | more shared electrons, stronger force, smaller length and higher bond enthalpy |
| what is molecular shape determined by | repulsion between the electron pairs surrounding the central atom |
| what are the different names for each shape of a molecule | 2 ELECTRON PAIRS linear 3 ELECTRON PAIRS trigonal planar bent 4 ELECTRON PAIRS tetrahedral trigonal pyramidal bent 5 ELECTRON PAIRS trigonal bipyramidal seesaw distorted T 6 ELECTRON PAIRS octahedral square pyramidal square planar |
| what is electronegativity | ability of an atom to attract to the bonding electrons in a covalent bond |
| what is polarity | a difference in electronegativity |
| how to tell if something is more electronegative | increases with higher charge and smaller radius. therefore increases across period and up a group (or look at Pauling scale!!!) |
| what are the three types of IM forces | London dipole - dipole hydrogen |
| describe London forces | -occur in everything -can hold molecules in a lattice -stronger London forces when there are larger electron clouds, and larger surface area |
| describe dipole - dipole forces | -stronger than London forces -occur in polar molecules |
| describe hydrogen bonding | -strongest of them all -occurs between hydrogen and oxygen, nitrogen or fluorine -has high melting/boiling points |
| why does water have a high melting/boiling point | it can form hydrogen bonds, which are very strong and take a lot of energy to overcome |
| why does ice float/why is it less dense | lattice structure, so more space between the hydrogen bonds. As it melts, some bonds are broken allowing molecules to fill the space. This shows that it is much less dense and can therefore float on water. |
| why do alcohols have high boiling points | they always have a hydroxyl group, which is polar (oxygen negative hydrogen positive). this helps oxygen to form a hydrogen bond with another positive hydrogen |
| for a substance to dissolve in another, what has to happen | -bonds in the substance have to break -bonds n the solvent have to break -new bonds have to form between them |
| describe polar and non polar solvents | POLAR = polar molecules, but don't necessarily form hydrogen bonds NON-POLAR = non polar molecules such as hexane (where they balance each other out) |
| why can ionic substances dissolve in water | water is polar, and ionic substances also have charged parts. therefore the opposite charges will attract to form new bonds between the solvent and substance. |
| why can alcohols dissolve in water | they have a hydroxyl end which is polar, so will attract to the charged parts in H2O (H is positive, O is negative). it is less soluble than Ionics though since the alcohol chain isn't attracted to water |
| why can halogenoalkanes dissolve in water | they only have dipole dipole bonds so cant break the hydrogen ones in water. they will however bond with other dipole dipole bonded substances without hydrogen bonds. |
| state the properties of ionic bonding | POINTS - high STATE - solid SOLID CONDUCTS - no LIQUID CONDUCTS - yes SOLUBLE - yes |
| state the properties of simple covalent bonding | low usually gas/liquid (but iodine is solid) no no depends on hydrogen bonds |
| state the properties of giant covalent bonding | high solid no no no |
| state the properties of metallic bonding | high solid yes yes no |
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