3.1.1 Atomic structure

Question 1

model for atomic structure has changed multiple times, how did it begin?

Answer 1

• Plum pudding model
  initially thought that atoms consisted of a positively charged sphere with small negative charges distributed evenly within it

Question 2

Electron shell model ? (current model)

Answer 2

• atom consists of a small, dense, central nucleus
• surrounded by orbiting electrons in electron shells
• electrons were discovered by Rutherford in the scattering experiment (1911)

Question 3

the nucleus consists of…

Answer 3

• protons and neutrons giving it an overall positive charge
• contains almost the entire mass of the atom

Question 4

whats the relative mass of a proton, neutron and electron

Answer 4

p - 1
n - 1
e - 1/1840

Question 5

max number of orbiting electrons a shell can hold depends on what number shell it is. whats the formula to calculate it

Answer 5

2n squared

n is the number of the shell

DO N SQUARED FIRST THEN TIMES BY TWO

Question 6

how can the next shell hold electrons

Answer 6

by filling the previous shells

Question 7

What represents A

Answer 7

mass number (protons + neutrons)

Question 8

what does Z represent?

Answer 8

Atomic number (protons)

Question 9

what is relative atomic mass? (this formula takes into account relative abundance of diff isotopes

Answer 9

mean mass of atom of element
divided by
1/12 x mean mass of Carbon 12 isotope

Question 10

what are isotopes

Answer 10

atoms of the same element with the same atomic number but with diff number of neutrons (resulting in a diff mass number)

Question 11

how is an ion formed

Answer 11

when an atom loses or gains electrons meaning it is no longer neutral and ends up having an overall charge

Question 12

what is mass spectrometry

Answer 12

• an analyctic technique used to identify diff isotopes and find the overall relative mass of an element

Question 13

what is TOF - time of flight - mass spectrometer

Answer 13

this records the time it takes for ions of each isotope to reach a detector
using this, a spectra can be produced showing each isotope present

Question 14

how does TOF work

Answer 14

1 - ionisation - a sample of an element is vapourised and injected into the MS
- a high voltage is passed over the chamber causing electrons to be removed (ionised) from the atoms leaving +1 charged ions

2 - Acceleration - these positively charged ions are then accelerated towards a negatively charged detection plate

3 - Ion drift - the ions are then deflected by a magnetic field into a curved path. the radius of their path is dependant on the charge and mass of the iron

4 - Detection - when positive ions hit the negatively charged detection plate, they gain an electron producing a flow of charge
the greater the abundance, the greater the current produced

5 - Analysis - these current values are then used in combination with the flight times to produce a spectra print out with the relative abundance of each isotope displayed

Question 15

during the ionisation process, what could be produced and what does this mean

Answer 15

• A 2+ charged ion may be produced
• This means it will be more affected by the magnetic field causing a curved path of smaller radius
• As a result, its mass to charge ration (m/z) is halved and this can be seen on spectra a trace at half the expected m/z value

Question 16

Using a spectra, how can the Ar can be calculated

Answer 16

(m/z) x abundance
divided by
total abundance

Question 17

what is a spectra

Answer 17

the lines shown on the mass spectrum graph

Question 18

what charasteristic pattern is shown in the spectra of chlorine?

Answer 18

3:1 ratio for Cl+ ions and a 3:6:9 ration for Cl2+ ions
- bc one isotope is more common so can be formed in more combinations

Question 19

how many orbitals are there and what is another name for them?

Answer 19

there are 4 : s, p ,d, f
- they are also called shells

Question 20

what is the max each orbital can hold

Answer 20

Has to be full first before they move to next orbital
s - 2 electrons
p - 6 electrons
d - 10 electrons

Question 21

within an orbital, why do electrons pair up with the opposite spin?

Answer 21

so atom is as stable as possible
- HAS to be same orbital - opposite spin
this spin is represented by arrows

Question 22

there are 3 rules for electric configuration, what are they?

Answer 22

1 - the lowest orbital is filled first
2 - electrons with the same spin fill up an orbital first before pairing begins
3 - no single orbital holds more than 2 electrons

Question 23

whats the exception to the oposite spin rule

Answer 23

if electron spins are unpaired, hence unbalanced, it produces a natural repulsion between the electrons making the atom very unstable
- if this is the case, electrons may take on a diff arrangement to improve stability
FROM 3p⁴ TO 3p³4s¹