The Atom and Redox Flashcards
Structure of an atom
Proton- nucleus- 1 - +1
Neutron- nucleus- 1- 0
Electron- Electron shells- 1/2000, -1
Define relative isotopic mass
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
How to calculate relative atomic mass
- multiply the relative isotopic mass by the % abundance
- Add these together
- Divide by 100
Relative atomic mass
The weighted mean mass of an atom of an element compared with 1/12 of the mass of an atom of carbon-12
What does a mass spectrometer measure
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
Mass spectrometer graph
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.
Define relative molecular mass
The weighted mean mass of a molecule of a compound compared with 1/12 of the mass of an atom of carbon-12
Define relative formula mass
The weighted mean mass of a formula unit of a compound compared with 1/12 of the mass of one atom of carbon-12
Define 1st ionisation energy
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-
3 Factors that affect ionisation energy
- Atomic radius- further the distance, the weaker the electrostatic attraction, lower IE
- Nuclear charge- the higher the nuclear charge, stronger the electrostatic attraction, the higher the IE
- E- shielding- The more inner shells of e-, the greater the shielding effect, the weaker the electrostatic attraction , the lower the IE
Why is the second ionisation energy always greater than the first
Every time an electron is removed, the electrons are pulled closer to the nucleus, so more energy is needed to overcome this.
Succesive ionisation energies graphs
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
Photoelectron spectrum graphs
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.
General trend of IE across a period
It increases
- number of electrons shielding stay relatively similar- no new shells
- nuclear charge increases- increases attraction between nucleus and electrons- more IE needed
- Atomic radius decreases - increases attraction- higher IE
Different orbitals
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
Number of electrons that subshells can contain
s- 2
p- 6
d-10
What is electron configuration of Mg, Ge (using shortened form for Ge)?
mg - 1s2 2s2 2p6 3s2
Ge- [Ar] 3d10 4s2 4p2
What fills first the 3d or 4s
4s but 3d is written first
What are two exceptions to the rules- 4s only has electron when 3d fills up
Copper and chromium
Define Oxidation
Is the loss of electrons
gain of oxygen
Define Reduction
Is the gain of electron
write oxidation half equation for Mg to Mg2+
Mg–> Mg2+ + 2e-
Write reduction half equation for Ag+ to Ag and Cl gas to Cl ions
Ag+ + e- –> Ag
Cl2 +2e- –> 2Cl-
Write full chemical equation for redox reaciton of chlorine gas to form Mg+ ions
Mg (s) + Cl2 (g) –> Mg2+ + 2Cl-
Define oxidising agent
Causes something else to be oxidised- is reduced
Define reducing agent
Causes something else to be reduced- is oxidised
Oxidation number rules
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
Why is Cu(NO3)2 called copper(II) nitrate(v)
Copper has oxidation state of +2
Nitrogen has oxidation state of +5
Define oxidation in terms of oxidation numbers
An increase in oxidaton number
Define reduction in terms of oxidation numbers
A decrease in oxidaton number
Describe difference in ionisation energy between nitrogen and oxygen- why it goes against general trend
- The ionisation energy decreases between nitrogen and oxygen
- because in nitrogen 1 electron is in each of the p orbitals
- 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
- this causes electron repulsion between the pair of electrons making it slightly easier to remove
General trend of IE down a group
- The IE decreases
- more electrons shielding-decreases electrostatic attraction between the outer electrons and the nucleus
- Atomic radius increases- decreases attraction
- This overcomes the increase in nuclear charge which would increase the IE.
