Atomic structure and emission spectra Flashcards
Isotope def
Different versions of an element with the same number of protons but different number of neutrons
Relative isotopic mass
Mass of a particular isotope of an element relative to one twelfth of mass of carbon-12.
Relative atomic mass
Weighted average of all naturally occurring isotopes of an element relative to one twelfth of mass of carbon 12.
First ionisation energy def
Energy required to remove one mole of electrons from one mole of gaseous atoms.
M(g) -> M+(g) + e-
2nd ionisation energy etc.
Energy required to remove one mole of electrons from one mole of 1+ (and etc.) gaseous ions.
Things that govern ionisation energy
Nuclear charge
Electron shielding, electron shielding is a much more significant factor than nuclear charge.
Why does first ionisation energy decrease down group 1?
Despite nuclear charge up, number of shells up, meaning more shielding between nucleus and outer electron and less effective nuclear charge so less energy required to remove it.
Why general increase in first ionisation energy across a period?
Nuclear charge increases with number of protons. Same shells therefore similar shielding.
How is atomic emission spectra made?
Made by exciting electrons via heat/electricity to excite them to higher energy level. As they go back down to lower energy levels, specific wavelengths of electromagnetic radiation is emitted and detected.
What does a line spectra prove?
That electrons can only exist at certain energy levels (shells) rather than any as only certain energy transitions are possible.
What is successive ionisation?
Sequential removal of all electrons surrounding an atom from highest energy level to lowest. Each electron removed requires more energy.
Why is successive ionisation energy much higher when going to a new shell?
Reduced shielding, Z eff increased, more attraction.
Also proof for shells.
How many orbitals in an s, p and d subshell?
1, 3, 5
Shape of each subshell
Google it
What is up spin?
+1/2 or half arrow upwards
What is down spin?
-1/2 or half arrow downwards
What is orbital?
Region within an atom that can hold up to two electrons with opposite spins. 90% chance of finding electron inside.
What is Hund’s rule of Maximum Multiplicity?
Electrons in the same subshell will fill all available orbitals singly before pairing in the same orbital as it minimises electron repulsion.
Pauli’s Exclusion principle
No two electrons can have the same 4 quantum numbers and so if the electrons are in the same orbital, they must have opposite spin.
Order that subshells fill
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, order on periodic table
Aufbau principle
Electrons must fill orbitals from lowest energy state - ‘ground state’.
Electron config of Cr
[Ar] 4s1 3d5
Electron config of Cu
[Ar] 4s1 3d10
Why is the electron config of Cr and Cu different?
To reduce repulsion in the 4s shell, a 4s electron is promoted to the 3d subshell to create a half/fully filled shell which is at a lower energy state.
Ionisation of transition metals
Remove 4s electrons first when ionising
What part of an element determines its chemical properties
Electronic config
Why does first ionisation energy decrease from Be to B despite nuclear charge increasing?
This is because the outer electron removed in B is from the 2p subshell and therefore has increased shielding from the 2s subshell electrons. Zeff is therefore lower and less energy is required to remove electron.
Why does first ionisation energy decrease from N to O despite nuclear charge increasing?
The outer electron in O is paired in the 2p subshell whereas in N it is not. Therefore, there is increased electron repulsion and less energy is required to remove the electron.
