The Atom and Redox

Question 1

Structure of an atom

Answer 1

Proton- nucleus- 1 - +1
Neutron- nucleus- 1- 0
Electron- Electron shells- 1/2000, -1

Question 2

Define relative isotopic mass

Answer 2

The mass of one atom of a specific isotope of an element compared the 1/12 of the mass of one atom of carbon-12

Question 3

How to calculate relative atomic mass

Answer 3

1. multiply the relative isotopic mass by the % abundance
2. Add these together
3. Divide by 100

Question 4

Relative atomic mass

Answer 4

The weighted mean mass of an atom of an element compared with 1/12 of the mass of an atom of carbon-12

Question 5

What does a mass spectrometer measure

Answer 5

The relative abundance of an isotope.
Atoms are deflected by a magnetic field if they are first converted into a positive ion .
Electrically charged particles are affected by the magnetic field neutral ones aren’t.
The deflected ions are detected and displayed on a mass spectrum as a mass-to-charge ratio m/z

Question 6

Mass spectrometer graph

Answer 6

on x axis m/z (mass to charge ratio)
On y axis relative abundance
To work out relative abundance of each isotope add up all the heights of the peaks, then divide one peak by the total heights and multiply by 100.

Question 7

Define relative molecular mass

Answer 7

The weighted mean mass of a molecule of a compound compared with 1/12 of the mass of an atom of carbon-12

Question 8

Define relative formula mass

Answer 8

The weighted mean mass of a formula unit of a compound compared with 1/12 of the mass of one atom of carbon-12

Question 9

Define 1st ionisation energy

Answer 9

The energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions.
K (g) –> K+ (g) + e-

Question 10

3 Factors that affect ionisation energy

Answer 10

1. Atomic radius- further the distance, the weaker the electrostatic attraction, lower IE
2. Nuclear charge- the higher the nuclear charge, stronger the electrostatic attraction, the higher the IE
3. E- shielding- The more inner shells of e-, the greater the shielding effect, the weaker the electrostatic attraction , the lower the IE

Question 11

Why is the second ionisation energy always greater than the first

Answer 11

Every time an electron is removed, the electrons are pulled closer to the nucleus, so more energy is needed to overcome this.

Question 12

Succesive ionisation energies graphs

Answer 12

Help you to know how many electrons there are in each shell.
So you can predict the group an element is in.
e.g. if the biggest gap in energies is between 4th and 5th electron is suggests they are in group 4

Question 13

Photoelectron spectrum graphs

Answer 13

IE on x axis increasing from right to left
Relative number of electron on y axis
The amount of energy needed to remover one electron from a particular energy level determines where along the horizontal axis the peak is positioned.
the number of electrons within an energy level determines the height of each peak.

Question 14

General trend of IE across a period

Answer 14

It increases

1. number of electrons shielding stay relatively similar- no new shells
2. nuclear charge increases- increases attraction between nucleus and electrons- more IE needed
3. Atomic radius decreases - increases attraction- higher IE

Question 15

Different orbitals

Answer 15

S-orbital - is spherical, contains 2 electrons in orbital
P-orbital - is dumbbell shape, p sub-shell contains 3 orbitals each can contain 2 electrons.
d-orbital

Question 16

Number of electrons that subshells can contain

Answer 16

s- 2
p- 6
d-10

Question 17

What is electron configuration of Mg, Ge (using shortened form for Ge)?

Answer 17

mg - 1s2 2s2 2p6 3s2

Ge- [Ar] 3d10 4s2 4p2

Question 18

What fills first the 3d or 4s

Answer 18

4s but 3d is written first

Question 19

What are two exceptions to the rules- 4s only has electron when 3d fills up

Answer 19

Copper and chromium

Question 20

Define Oxidation

Answer 20

Is the loss of electrons

gain of oxygen

Question 21

Define Reduction

Answer 21

Is the gain of electron

Question 22

write oxidation half equation for Mg to Mg2+

Answer 22

Mg–> Mg2+ + 2e-

Question 23

Write reduction half equation for Ag+ to Ag and Cl gas to Cl ions

Answer 23

Ag+ + e- –> Ag

Cl2 +2e- –> 2Cl-

Question 24

Write full chemical equation for redox reaciton of chlorine gas to form Mg+ ions

Answer 24

Mg (s) + Cl2 (g) –> Mg2+ + 2Cl-

Question 25

Define oxidising agent

Answer 25

Causes something else to be oxidised- is reduced

Question 26

Define reducing agent

Answer 26

Causes something else to be reduced- is oxidised

Question 27

Oxidation number rules

Answer 27

1. Atoms of uncombined elements- 0
For combined elements in compounds
2. Group 1 atoms - +1
3. Group 2 atoms- +2
4. Fluorine atoms- -1
5. Oxygen atoms- -2 except in a peroxide- -1
6. Hydrogen atoms- +1 except in a hydride- -1
7. Ions - are charge of ions

Question 28

Why is Cu(NO3)2 called copper(II) nitrate(v)

Answer 28

Copper has oxidation state of +2

Nitrogen has oxidation state of +5

Question 29

Define oxidation in terms of oxidation numbers

Answer 29

An increase in oxidaton number

Question 30

Define reduction in terms of oxidation numbers

Answer 30

A decrease in oxidaton number

Question 31

Describe difference in ionisation energy between nitrogen and oxygen- why it goes against general trend

Answer 31

1. The ionisation energy decreases between nitrogen and oxygen
2. because in nitrogen 1 electron is in each of the p orbitals
3. in oxygen 1 electron is in each p orbital and then one electron goes in the same orbital as one of the other electrons- a pair of electrons in the same orbital
4. this causes electron repulsion between the pair of electrons making it slightly easier to remove

Question 32

General trend of IE down a group

Answer 32

1. The IE decreases
2. more electrons shielding-decreases electrostatic attraction between the outer electrons and the nucleus
3. Atomic radius increases- decreases attraction
4. This overcomes the increase in nuclear charge which would increase the IE.