Atomic structure Flashcards
What is Ionisation Energy?
The minimum amount of energy required to remove a mole of electrons from a mole of atoms in a gaseous state
What are the 3 factors that affect ionisation energy?
- Distance of outer electron to nucleus
- Shielding
- Nuclear charge
State the general trend in Ionisation Energy across a period
- General increase
- Same shielding
- Increase in protons, which increases nuclear charge, meaning there is a stronger nuclear attraction on the outer electron which requires more energy to lose
State the trend of ionisation energies down a group
- Decrease
- More shells between nucleus and outer electron shell, increases shielding so there is a weaker nuclear attraction on outer electron which requires less energy to lose
State the trend in atom sizes across a period
- Decrease in size
- Same shielding
- Increase in protons so higher nuclear charge, so a greater nuclear attraction on outer electron which pulls the outer shell closer
How many electrons and orbitals are in each block?
- s: 1 orbital and 2 electrons
- p: 3 orbitals and 6 electrons
- d: 5 orbitals and 10 electrons
- f: 7 orbitals and 14 electrons
Which orbitals do electrons fill first?
- Fill orbitals with the lowest energy levels
- The further away from the nucleus the higher the energy
- Fill empty orbitals on that energy level first
What is the general rule for electrons in the 4s subshell?
First in, first out
What are the exceptions in the 3d subshells and why?
- Chromium: An electron from the 4s subshell goes into the empty orbital in 3d to make it half-full since that is more stable than a partially full subshell
- Copper: An electron from the 4s subshell goes into the last half full orbital to make the subshell completrely full since that is more stable than a partially full subshell
State the full electronic configuration of Chromuim
1s2 2s2 2p6 3s2 3p6 4s1 3d5
State the full electronic configuration of Copper
1s2 2s2 2p6 3s2 3p6 4s1 3d10
State the full electronic configuration of Fe2+
1s2 2s2 2p6 3s2 3p6 3d6
State the full electronic configuration of Silver
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d10
Which element has the electronic configuration [Kr] 5s1 4d5 ?
Molybdenum
How and why does the IE of Boron deviate from the general trend in period 2?
- IE is lower than Beryllium’s
- The electron to be removed from Be is in 2s subshell whereas the electron from B is in 2p subshell
- 2p subshell is higher in energy than 2s subshell so less energy is needed to remove the electron from boron
How and why does the IE of Oxygen deviate from the general trend in period 2?
- IE is lower than Nitrogen’s
- Outer electron in N is unpaired, whereas electron in O is paired
- Paired electrons repel therefore less energy is needed to remove the electron from Oxygen
What are the 2 factors that are measured in Mass Spectrometry?
- Relative abundance of isotopes
- Mass/charge ratio
Why is the inside of a Mass Spectrometer a vacuum?
To prevent collision with air particles
Why are sample particles ionised?
- So they can be accelerated towards the negatively charged plate
- So they can generate a current when they hit the detector
How is the ion accelerated?
- Positive ions are attracted to the neratively charged plate
- All ions have the same KE
How are ions sperated in the flight tube?
Smaller, lighter ions travel faster than larger, heavier ions and move ahead
How are ions detected?
- Each ion hits the detector and gains an electron
- This generates a current
- The size of this current is proportional to the abundance of the ion
How are molecules ionised in electron impact?
- High energy electron
- From an electron gun is fired at the sample
- One electron from each particle is knocked off
- Forms a 1+ ion/ positively charged
What is the general formula of an ion which has been ionised by electron impact?
(Use M as your element)
M(g) -> M+(g) + e-
How are molecules ionised in electro spray?
- Sample dissolved in volatile solvent
- Passed through hypodermic needle
- Connected to high voltage power supply to create a fine mist
- Each particle gains a proton (H+) to form a positive charge
What is the formula for kinetic energy?
KE = ½ x m x v²
What are the 2 formulas for velocity?
v = √2KE ⁄ m
v = d ⁄ t
What is the formula for mass?
(in terms of KE)
m = 2KE ⁄ v²
What is Avagadros constant?
6.022 x 10^23
What is the formula for finding the mass?
(Using the mass number)
mass in Kg = mass no. x 10^-3 ⁄Avagadros constant
What is the definition of relative atomic mass?
A weighted average of all isotopes of an element taking into account their abundance
How, if at all, do isotopes of the same elements differ in terms of chemical properties and why?
- They don’t since they have the same electronic configuration
What are 2 differences between the plum pudding model and the current model?
- Nucleus contains protons and neutrons
- Electrons in shells orbiting the nucleus
What is the period 3 element witht the highest second ionisation energy?
Sodium
- Has full outer shell
Explain why a fluoride ion is larger than a sodium ion
(2 marks)
- Same electronic configuration and shielding
- Fluoride ion has less protons/ lower nuclear charge
- Weaker attraction between nucleus and outer electrons
Why is the second ionisation energy of calcium lower than that of potassium?
(2 marks)
- Outer electron in Ca is further from nucleus/ removed from a higher energy level
- More shielding in Ca+
