atomic structure

Question 1

define atomic number

Answer 1

is equal to the number of protons

Question 2

define mass number

Answer 2

equal to the number of protons and neutrons combined

Question 3

cations

Answer 3

lost electrons
positive ions

Question 4

anions

Answer 4

gained electrons
negative ions

Question 5

define isotopes

Answer 5

same number of protons but different number of neutrons

Question 6

why do isotopes have the same chemical properties

Answer 6

they have the same electron configuration

Question 7

what is the relative mass and charge of a proton

Answer 7

1 and +1

Question 8

what is the relative mass and charge of neutron

Answer 8

1 and 0

Question 9

what is the relative mass and charge of electron

Answer 9

1/1840 and -1

Question 10

define ionisation energy

Answer 10

the amount of energy needed to remove one mole of electrons from a mole of atoms in the gaseous state

Question 11

explain a small jump in successive ionisation energies

Answer 11

removed from a ore positive ion

Question 12

explain a big jump in successive ionisation energies

Answer 12

there on different shells closer to the nucleus so less shielding

Question 13

what shape does a s orbital have and how many sub shells are there in it

Answer 13

spherical shape
one s orbital

Question 14

what shape does a p orbital have and how many sub shells are there in it

Answer 14

dumbbell shape
3

Question 15

what shape does a d orbital have and how many sub shells are there in it

Answer 15

three p orbitals
5

Question 16

why electron on an atom has the highest energy

Answer 16

outer most electron because i is furtherest from the nucleus

Question 17

what are the exceptions to electron configurations

Answer 17

chromium (more stable if 3d is exactly half full)
copper (more stable if 3d is full)

Question 18

what is the trend in IE across period 3 and why

Answer 18

general increase
there is a greater nucleus charge across period 3
same amount of shielding
so greater attraction between the nucleus and outer electron

Question 19

explain why Al has a lower 1st IE than magnesium

Answer 19

the first e- removed from Mg is from a 3s sub shell
the first electron removed from Al is from a 3p sub shell
the 3s sub shell is lower in energy than 3p
therefore less energy is needed to remove the electron from Al

Question 20

explain why S has a lower 1st IE then Phosphorous

Answer 20

the first e- removed from p is from a 3p sub shell and is unpaired
the first e- removed from s is also from a 3p sub shell but is from a paired orbital
this means s has a lower IE due to electron pair repulsion
therefore less energy is needed to remove the electron from s

Question 21

how does the ionisation energy change down a group

Answer 21

atoms get bigger
more shielding
weaker attraction from nucleus to electron in outer shell
ionisation energy decreases down group

Question 22

state and explain the trend in atomic radius down a group

Answer 22

atomic radius increases
the number of shells increases so the amount of shielding increases

Question 23

why does the atomic radius gets smaller from right to left across a period

Answer 23

the nuclear charge increases
there is a greater attraction between the electrons and the nucleus the amount of shielding stays the same

Question 24

briefly outline how a time of flight mass spectrometer works

Answer 24

an unknown mixture is injected into a mass spectrometer, it is converted into positive ions, accelerated to high speed, and then arrived at a detector

Question 25

describe the vacuum

Answer 25

the entire machine is a vacuum inside to prevent an of the particles being tested colliding with molecule from the air

Question 26

what are the 2 types of ionisation

Answer 26

electron impact
electrospray

Question 27

describe acceleration

Answer 27

the positive ions attracted to a negatively charged plate and accelerate towards it
once accelerated all ions will have same kinetic energy

Question 28

describe ion drift

Answer 28

particles travels t different speeds

Question 29

describe detection

Answer 29

this generates a current the size of which is proptional to the number of each type of ion

Question 30

how are ions detected

Answer 30

each ion hits the detector
ions gain an electron
generates a current
size of current is proptional to the abundance of the ion

Question 31

how are ions separated in the flight tube

Answer 31

ions travelling at higher speeds (small m/z) move ahead of those travelling at more slow speeds (large m/z)

Question 32

describe electron impact ionisation

Answer 32

the sample is vaporised and then high energy electrons are fried at it

the high energy electrons come from an electron gun which is a hot wire filament with a current running threw it that emit electrons
this knocks of one electron forming a 1+ ion

Question 33

describe electrospray ionisation

Answer 33

the sample is dissolved in a volatile solvent and injected through a fine hypodermic needle to give a fine mist
the tip of the needle is attached to the positive terminal of a high voltage power supply

the particles are ionised b gaining a proton

Question 34

which ionisation technique is fragmentation more likely to take place

Answer 34

electron impact ionisation

Question 35

kinetic energy equation

Answer 35

Ke = 1/2 mv^2

Question 36

what is equation for time of flight

Answer 36

t= d/v

Question 37

calculating mass from mr

Answer 37

mr divde by thousand divde by avogadro constant