Last Minute As Chemistry Revision

Front 1

definition of mass number

Back 1

number of protons plus number of electrons

Front 2

definition of atomic number

Back 2

number of protons

Front 3

relative atomic mass

Back 3

average mass of one atom of an element compared to 1/12th mass of an atom of carbon-12

Front 4

relative molecular mass

Back 4

avarage mass of one molecule compared to 1/12th mass of an atom of carbon-12

Front 5

what are the four key stages of a mass spectrometer?

Back 5

ionisation, acceleration, deflection, detection

Front 6

what happens when an ion hits the detector in a mass spectrometer?

Back 6

they lose their charge and create a current which is proportional to the abundance of each ion.

Front 7

which ions travel fastest in a mass spectrometer?

Back 7

the lightest ones

Front 8

what does the deflection of an ion depend on?

Back 8

its m/z (mass to charge ratio)

Front 9

which ions are deflected the most by the magnet?

Back 9

the lighter ones

Front 10

which groups are the s block?

Back 10

group 1 and 2

Front 11

which groups are in the d block?

Back 11

transition metals

Front 12

which groups are in the p block?

Back 12

group 3 to 0

Front 13

which groups are in the f block

Back 13

lanthanides

Front 14

what is the general trend in boiling points and melting points in period three?why?

Back 14

they increase until group 5 when they start to drop. group 1,2 and 3 have giant metallic structures whose strength increases with more delocalised electrons. group 4 has a giant covalent structure which is held together in layer by strong covalent bonds. but group 5,6,7 are molecular structures which tend to have low mp/bp, this is is becuase they have strong covelent bonds within the molecules but weak van der waalls forces between the molecules

Front 15

what is the exception to the general trend in boiling points and melting points of period three? why?

Back 15

sulfur (group 6), it increases rather than decreases, becuase it is a much bigger molecule (s8) and therefore has stronger van der waals forces because of the large amount of electrons.

Front 16

why do first ionisation energies increase across a period?

Back 16

because the number of protons in the nucleus increase but the main energy level that the outer electrons are in stays the same so with the increase in nuclear charge it is increasingly difficult to remove electrons.

Front 17

which group has the highest ionisation energies?

Back 17

group 0/ group 8

Front 18

why do ionisation energies decrease as you go down a period?

Back 18

because the energy level that the outer electrons are in get higher so their is an increase in shielding. also the atomic radii increases so the electron being removed is further away from the nucleus so the electrostatic forces between the outer electrons and the nucleus are weaker. therefore the electrons get easier to remove as you go down the group

Front 19

what is avagadro's number?

Back 19

6.022x10 to the power of 23/ 1 mole

Front 20

how do you work out atom economy?

Back 20

mass of the desired product divided by total mass of reactants x 100. (big numbers must be taken into account)

Front 21

how do you work out percentage yield?

Back 21

number of moles of a specific product divided by the theoretical maximum number of moles of the product x 100

Front 22

what makes the strength of a metallic bond increase?

Back 22

the number of delocalised electrons and the size of ion. more delocalised electrons= stronger bond. smaller ions so the delocalised electrons are closer to the nucleus = stronger bond.

Front 23

what three things must you remember when displaying a hydrogen bond?

Back 23

the dashed line, all lone pairs and slightly positive and slightly negative delta signs.

Front 24

what must you always remember when writing out an ionisation energy equation?

Back 24

gas state symbols

Front 25

what structure do ionically bonded compounds have? what forces hold them together? hat properties does this give them?

Back 25

giant structures. they are held together by electrostatic forces. therefore they have a high melting point. they are brittle when force is applies the ions can line up and repel each other causing them to shatter.

Front 26

when do ionic compounds conduct electricity?

Back 26

when they are molten or in solution because the ions are free to move.

Front 27

why do molecular structures have such low melting points?

Back 27

because they have strong covalent bonds holding the atoms within the molecules together but weak inter molecular forces holding the molecules together.

Front 28

what gives metallic crystals such high melting points?

Back 28

the strong metallic bonds.

Front 29

what are the properties of diamond and why do these properties exist?

Back 29

it is the hardest substance known to man, it has a very high melting point (over 3700k) becuase of the carbon atoms have four strong covalent bonds holding it together (much stronger than inter molecular forces). diamond doesn't conduct electricity becuase there are no free charged particles

Front 30

what shape do the molecules of diamond take and what are the bond angles?

Back 30

tetrahedron - 109.5 degrees

Front 31

what are the properties of graphite and why do these properties exist?

Back 31

each carbon atom have three single covalent bonds holding together the layers of carbon atoms. the layers are held together by van der waals forces so they have high melting points but are very brittle. it does conduct electricity across the planes of hexagons because of the 1 free electron from each carbon atoms.

Front 32

what shape do the molecules of graphite take and what are the bond angles?

Back 32

trigonal planar - 120 degrees.

Front 33

definition of electronegativity?

Back 33

the power of an atom to attract electron density in a covalent bond towards itself.

Front 34

definition of polarity?

Back 34

the unequal sharing of the electrons between the atoms that are covalently bonded.

Front 35

what does electronegativity depend on?

Back 35

the nuclear charge, distance between the nucleus and outer shell electrons and shielding. smaller the atom, the greater the electronegativity. the larger the nuclear charge the greater the electronegativity.

Front 36

what happens to electronegativity as you go across a period and up a group?

Back 36

it increases both ways.