Atomic Structure Flashcards
(46 cards)
1
Q
Timeline of model of the atom
A
- Democritus
- John Dalton
- J.J Thompson
- Rutherford
- Neils Bohr
- James Chadwick
2
Q
Democritus
A
- Greek philosopher
- atomos = indivisible
- atoms could not be split
3
Q
John Dalton
A
- came up with atomic theory
- all matter composed of atoms
- they are indivisible and indestructible building blocks
- represented atoms as hard spheres that couldn’t be split
- atoms of an element were identical
- different elements had atoms of different size and mass
4
Q
J.J Thompson
A
- atoms were indivisible
- discovered atoms contained negatively charged particles (electrons)
- put forward plum pudding model
- atoms were spheres of positive charge with negative electrons randomly embedded throughout
- realised when discovering electrons that atoms could not be solid spheres and could be broken down into smaller subatomic particles
5
Q
Rutherford
A
- gold foil experiment proves that plum pudding model was incorrect
- fired positively charges alpha particles through gold foil
- proved that atoms have their positive charge concentrated in a very tiny volume and that most of the atom was completely empty space
- if the plum pudding model correct, then most of the alpha particles fired at the gold foil would be deflected, but most passed straight through
6
Q
Niels Bohr
A
- if electrons were a ‘cloud’ around the nucleus then it would spiral sown into the he nucleus causing it to collapse
- thus Bohr proposed a new theory:
- electrons can only exist in fixed orbits/shells
- each shell has a fixed energy
7
Q
Niels Bohr revised model
A
- scientists discovered that not all electrons in the same shell had the same energy
- meant somehow the previous Bohr model wrong
- refined to add sub-shells/orbitals
- Bohr believed each shell can only hold a fixed number of electrons
- also, elements reactivity is due to its electrons, so when the shell is full, it is inert.
- modified Bohr model includes the idea of sub shells and orbitals and we still use this model to explain basic ideas about bonding
8
Q
James Chadwick
A
- devised an experiment to prove the existence of neutrons
9
Q
Different sub-atomic particles
A
- nucleons = protons + neutrons
- electrons
10
Q
Properties of subatomic particles
- proton
- neutron
- electron
A
11
Q
Isotopes
A
- Atoms with the same number of protons and electrons but different number of neutrons
- They have the same atomic number but a different mass number
- the reactivity of isotopes are identical as they have the same number of electrons
12
Q
Atomic number
A
The number of protons
13
Q
Mass number
A
Total number of protons an neutrons
14
Q
What affects the reactivity of an element
A
The number of electrons
15
Q
Equation for RAM
A
Ar = sum of the abundance x atomic number / total number of abundance
16
Q
Relative atomic mass (RAM) (Ar)
A
The relative atomic mass is the average mass of its atoms compared to 1/12 the mass of a carbon-12 atom
17
Q
Calculate the abundance of the different Chlorine molecules
A
18
Q
Different stages of TOF
A
- Ionisation
- Acceleration
- Flight Tube (Ion drift)
- Detection
19
Q
Stage 1 Ionisation for elements and low Mr compounds
A
- for ionisation to colour it has to be a gas
- high energy electron are fired by an electron gun
- this knocks out an electron of each particle
- the particle becomes a positive ion
20
Q
Stage 1 Ionisation for high Mr compounds
A
- ionisation is in an aqueous solution (sample in a volatile solvent)
- passed through a hypodermic needle attached to positive terminal of high voltage power supply
- the particle gains a proton
21
Q
Equation for Stage 1 elements and low Mr
A
22
Q
equation for stage 1 ionisation with high Mr compounds
A
23
Q
Stage 2 acceleration
A
- the positive ions are accelerated by using an electric field
- the ions are accelerate so that they have the same kinetic energy
24
Q
Stage 3 flight tube (ion drift)
A
- particles have the same kinetic energy
- ions with a smaller mass will travel faster along the tube
25
Stage 4 detection (3 marks)
- positive ions hit the negative plate and produce and electric current
- the electrons move from the plate to the ion
- the size of current is proportional to the number of ions
26
Equations for TOF
```
KE = 1/2mv^2
t = d/v
```
27
Two types of ionisation
```
Electron impact (gun)
Electrospray (needle)
```
28
How to calculate the mass of an ion
1 mole of Mass of element/1000 to get into kg
| Then ANS/6.022x10^23 To get mass of 1 ion in kg
29
What is a species
- atom or molecules
30
Why is there a small peak at the Mr+1
31
What are the different orbitals?
s, p, d, f
32
How many electrons can an s orbital hold
2
33
How many electrons can a p orbital hold
6
34
How many electrons can be held on a d orbital
10
35
Electronic configuration of Chromium
[Ar} 4s1 3d5
Not [Ar] 4s2 3d4
36
Electronic Configuration of copper
[Ar] 4s1 3d10
Not [Ar] 4s2 3d9
37
What is the first ionisation energy
- this is the energy needed to remove one mole of electrons from
- one mole of atoms in their gaseous state
- to form one mole of 1+ ions (also in their gaseous state)
38
Ionisation energy down a group
- ionisation energy decreases
- atomic radius increases
- more shells/shielding
- weaker attraction between nucleus and OUTER electron
39
Equation for first ionisation, second ionisation energy…
40
General trend of ionisation energy across a period
- increases
- smaller atomic radius
- more protons
- stronger forces of attraction between nucleus and OUTER electron
- same shielding/ same shells
41
Why does going from group two to three dip in ionisation energy
- going to a different sub shell, eg 2s to 2p and p is a higher energy than s
- the distance is further away
- so the forces of attraction is weaker between nucleus and electron
- less energy required to remove the electron
42
Why does it dip from group 5 to group 6 in ionisation energy
- there is an electron pair repulsion
- p e- from orbital with one e-
- s e- from orbital with two e-
- there is more electron electron repulsion in s
43
Successive ionisation energy
- atoms with more than one electron can have them successfully removed
44
Second ionisation energy
- the energy required to remove one mole of electrons
- from one mole of gaseous unipostive ions
- to form one mole of gaseous dispositive ions
45
Trend of successive ionisation energy
- increases as the electron is being pulled away from a more positive species
A large increase occurs when there is a change of shell because there is a big decrease in shielding - large increases can be used to predict the group of an unknown element
46
What does it mean if there is a really big number jump in successive ionisation energy
This shows which group the element is in
