Atomic Structure

Question 1

Define isotope

Answer 1

isotopes are atoms of the same element with different numbers of neutrons

Question 2

What decides the chemical properties of an element? And how does this effect isotopes

Answer 2

number and arrangement of electrons decides the chemical properties

isotopes have the same configuration of electrons so they have the same chemical properties

Question 3

Why do isotopes of an element have slightly different physical properties?

Answer 3

physical properties tend to depend on the mass of the atom

Question 4

19th century: What did John Dalton say atoms were?

Answer 4

Solid spheres
Different spheres made different elements
(All atoms of an element = same mass)

Question 5

1897: What did J.J. Thomson discover and what did it show?

Answer 5

Discovered the electron
Showed atoms weren’t solid
(Model known as ‘plum pudding model’)

Question 6

1909 - Ernest Rutherford: What did he find out?

Answer 6

Conducted the golden foil experiment:

Fired positively charged alpha particles at a very thin sheet of gold
Particles passed straight through gold & only small no. of particles were deflected backwards (pulm pudding model said = alpha particles would be deflected by the positive ‘pudding’ in atom)
= developed into nuclear model of atom
Tiny positive nucleus surrounded by ‘cloud’ of negative electrons - most of atom is empty space

Question 7

What was Niels Bohr’s model & discovery?

Answer 7

Model: where electrons exist in shells or orbits of fixed energy
Discovered: When electrons move between shells, electromagnetic radiation (with fixed energy or frequency) is emitted/absorbed

Question 8

What have modern day scientists discovered & so what did they do?

Answer 8

Electrons in same shell ≠ same energy
Bohr model = wrong ∴ they refined it & added sub-shells
(Isn’t perfect model but it’s simple and explains many experimental observations e.g. bonding & ionisation energy trends)

Question 9

Define relative atomic mass

Answer 9

the average mass of an atom compared to 1/12 mass of an atom of C12

Question 10

Define relative molecular mass

Answer 10

the average mass of a molecule compared to 1/12 mass of an atom of C12

Question 11

Relative masses can be measured by using a ____ ____________

Answer 11

mass spectrometer

Question 12

Step 1 is ______ and the 2 ways of doing this

Answer 12

ionisation

electrospray ionisation

electron impact ionisation

Question 13

Describe electrospray ionisation

Answer 13

The sample is dissolved and pushed through a small nozzle at high pressure. A high voltage is applied to it, causing each particle to gain a H+ ion. The sample is turned into a gas made up of positive ions.

Question 14

Describe electron impact ionisation

Answer 14

The sample is vaporised and an ‘electron gun’ is used to fire high energy electrons at it. This knocks one electron off each particles so they become +1 ions.

Question 15

Step 2 of mass spec is _____

Answer 15

Acceleration

Question 16

Describe acceleration

Answer 16

The positively charged ions are accelerated by an electric field so that they all have the same kinetic energy. ( This means that the lighter ions will move faster than the heavier ones)

Question 17

Step 3 of mass spec is _____

Answer 17

ion drift

Question 18

Describe ion drift

Answer 18

The ions enter a region with no electric field, so they just drift through it. Lighter ions will drift through faster than the heavier ones.

Question 19

Step 4 of mass spec is _____

Answer 19

detection

Question 20

Describe detection

Answer 20

because lighter ions travel at high speeds in the drift region, they reach the detector in less time than the heavier ones. The detector detects charged particles and a mass spectrum is produced.

Question 21

A mass spectrum is _____/______ plotted against _________

Answer 21

mass/charge

abundance

Question 22

Equation for calculating RAM when analysing spectra

Answer 22

RAM = m/z x abundance
____________________
total abundance

Question 23

If the relative abundance is not given in percentage when calculating RAM you need to…

Answer 23

divide answer by 100

Question 24

Elements with different _____ produce more than one line in a mass spectrum because the ______ have different masses.

Answer 24

isotopes

Question 25

A molecular ion, M+, is formed in the mass spectrometer when one electron is removed from the molecule. This gives a peak in the spectrum with a mass/charge ratio equal to ________ ________ ____ of the molecule. This can be used to help identify the unknown compound.

Answer 25

relative molecular mass

Question 26

Electron shells are made up of ___-______ and ________

Answer 26

sub-shells orbitals

Question 27

sub shell s p d number of 1 3 5 orbitals Max 2 ? ? electrons

Answer 27

6 10

Question 28

1. electrons fill up the ______ energy level first 2. electrons fill orbitals ________ first before they start sharing.

Answer 28

1. lowest 2. singly

Question 29

electron configuration of copper ?

Answer 29

1s2 2s2 2p6 3s2 3p6 4s2 3d9

Question 30

electron configuration of chlorine using noble gas?

Answer 30

[Ne] 3s2 3p5

Question 31

Define Pauli exclusion principle

Answer 31

Each orbital can hold a maximum of TWO electrons - must have opposite spins

Question 32

Define Hunds rule

Answer 32

When filling the orbitals of a sub level, put one electron in each orbital before pairing them

Question 33

Define Aufbau principle

Answer 33

lower energy levels fill before higher energy orbitals

Question 34

Define first ionisation energy

Answer 34

energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions

Question 35

Show the first ionisation energy of Na

Answer 35

Na(g) --> Na+(g) + e -

Question 36

ionisation depends on 3 things describe each shielding distance from nucleus nuclear charge

Answer 36

more energy levels = less attraction attraction decreases with distance more protons in the nucleus = more positively charged the nucleus is = stronger the attraction for the electrons

Question 37

A high ionisation energy means there's a high ___________ between the electron and the nucleus and so more ______ is needed to remove the electron.

Answer 37

attraction energy

Question 38

Define second ionisation energy

Answer 38

the energy needed to remove 1 electron from each ion in 1 mole of gaseous +1 ions to form 1 mole of gaseous ions with a +2 charge

Question 39

Show second ionisation energy of oxygen

Answer 39

O+(g) --> O2+(g) + e -

Question 40

Why is there 2 dips in the graph showing period 3 elements first ionisation energy?

Answer 40

dips on 3rd element and 6th element 3rd = change from s to p 6th = electron has paired to p orbital so it repels

Question 41

first ionisation energies of elements down a group ________

Answer 41

decrease

Question 42

first ionisation energies of elements across a period generally _______

Answer 42

increase

Question 43

Ionisation energy ________ down group 2

Answer 43

decreases extra inner shells to shield and extra shell means that the outer electrons are further away meaning less attraction to the nucleus so less attraction resulting in a lower ionisation energy

Question 44

ionisation energy _______ across a period

Answer 44

increases number of protons is increasing, which means a stronger nuclear attraction