chemistry AS level topic 2 bonding

Frage	Antworten
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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chemistry AS level topic 2 bonding

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	Erstellt von Talya Hambling vor etwa 9 Jahre