atomic structure

Question 1

relative atomic mass

Answer 1

the average mass of an element relative to 1/12 the mass of a carbon-12 atom

Question 2

mass number

Answer 2

the total number of protons and neutrons (nucleons) in an atom

Question 3

relative isotopic mass

Answer 3

the mass of an atom of an isotope relative to 1/12 the mass of a carbon-12 atom

Question 4

nucleon

Answer 4

sub-atomic particle with a relative mass of 1 that resides in the nucleus of an atom - protons and neutrons

Question 5

isotope

Answer 5

atoms of an element that have the same number of protons but different number of neutrons

Question 5

atomic number

Answer 5

number of protons

Question 6

relative atomic mass equation

Answer 6

(abundance x mass of isotope) / total abundance

Question 7

what is a mass spectrometer

Answer 7

measures masses of atoms and molecules by producing positive ions that are deflected by magnetic field

Question 8

what is mass spectrometry used for

Answer 8

• gives info about structure and chemical properties of molecules
• determine abundance of each isotope of an element
• identifies unknown compounds

Question 9

mass spectrum

Answer 9

highest peak is most abundant, number of peaks = number of isotopes

Question 10

ionisation energy definition

Answer 10

the energy required to remove 1 mole of electrons from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions (kJmol-1)

Question 11

stages in mass spectrometry

Answer 11

1. VAPORISATION - reduce pressure, heat, dissolve in volatile solvent then vaporise
2. IONISATION - beam of high energy electrons to knock off electrons, fragmentation can occur
3. ACCELERATION - electric field so all ions have some kinetic energy
4. SEPARATION - deflected by magnetic field (decrease mass increase deflection) OR time of flight (increased mass, decreased velocity, increased time)
5. DETECTION - beam of ions detected electrically

Question 12

successive IE

Answer 12

value of IE needed increases with each ionisation
- energy needed to overcome attraction from nucleus
- as each electron is removed the remaining ion becomes more positively charged
- removing the next electrons from increasing positive charge is harder as IE is larger

Question 13

IE across period

Answer 13

increases (more electrons in outer shell but they are in the same shell so the distance and shielding is similar, more protons in the nucleus so stronger electrostatic attraction between the electrons and protons so more energy is required to remove the electron)

Question 14

IE down group

Answer 14

decreases - (more shells between nucleus and outer shell so less attraction between outer electrons and nucleus so less energy required to ionise it)

Question 15

orbital definition

Answer 15

the volume of space that an electron fills in which there is a 95% probability of finding an electron

Question 16

Schrodinger equation

Answer 16

gives probability of finding an electron in a given volume of space because there is a cloud of negative charge

Question 17

s orbital

Answer 17

sphere - holds up to 2 electrons

Question 18

p orbital

Answer 18

dumbbell - holds up to two electrons each so when all p orbitals are full (3) there is 6 electrons

Question 19

d orbital

Answer 19

there are 5 orbitals so holds up to 10 electrons

Question 20

f orbital

Answer 20

there are 7 orbitals so holds up to 14 electrons

Question 21

d block

Answer 21

central section of the periodic table

Question 22

f block

Answer 22

two rows separated at bottom of periodic table (these elements fill the highest energy levels of the f orbitals when they place their last and highest electrons at the ground state)

Question 23

order of electronic arrangements

Answer 23

1s 2s 2p 3s 3p 4s 4p 3d

Question 24

why does group 3 have a lower first IE than group 2

Answer 24

(group 3 includes 3p subshell) 3p subshell is a higher energy than 3s and its shielded by its own 3s electrons so less energy needed to remove the electron

Question 25

why do group 6 elements have a lower first IE than group 5

Answer 25

in both groups the electron is removed from the same (3p) subshell but the electrons are paired for the first time in group 6. repulsion between paired electrons reduces energy required to remove electron

Question 26

melting point trend across period and why

Answer 26

increases up to group 4, then decreases (metallic bonding in group 1 and 2 so high mpt, group 4 giant covalent structure so very high mpt, after group 4 simple covalent molecules so low mpt)

Question 27

atomic radii across period trend

Answer 27

decreases as proton number increases so more attraction

Question 28

atomic radii down group trend

Answer 28

increases as more shells so electrons further from nucleus