atomic and electron structure: content Flashcards
how is relative atomic mass Aᵣ found
mass spectrometry
[detail not needed for OCR]
1) sample ionised (remove an e⁻)
2) ions fragment and are accelerated by a magnetic field
3) travel a distance dependent on the ratio (m/z) of their mass (m) and charge (z) and are detected
4) charge tends to equal +1 so mass can be easily calculated
resolution of Mᵣ/Aᵣ
1 decimal place (same as periodic table)
isotope masses should be given to
the nearest whole number (can’t have half a [proton])
how to calculate Aᵣ from a mass spectrum
Aᵣ = ∑(isotopic mass * relative abundance) ÷ total relative abundance
sub-shells
s: alkali and alkaline earth metals
p: post-transition metals, metalloids, nonmetals, halogens, noble gases
d: transition metals
f: lanthanides, actinides
order of increasing energy (electron structure)
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p …
how many orbitals in the s sub-level?
shape?
one orbital (two electrons)
spherical
how many orbitals in the p sub-level?
shape?
three orbitals (six electrons)
dumbbell shaped
how many orbitals in the d sub-level?
shape?
five orbitals (max ten electrons)
spherical
electron configuration exceptions?
chromium
- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵
copper
- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰
[one 4s electron goes to a new 3d orbital to minimise repulsion]
electron configuration of ions?
cations: e⁻ removed from highest energy orbital from the highest principal energy level
anions: e⁻ added to highest energy orbital from the highest principal energy level
which two subshells are closest in energy and what does this mean
3d and 4s
lead to anomalies: sometimes the lower energy (most stable) arrangement involves rearranging electrons within these levels
- one 4s electron goes to a new 3d orbital to minimise repulsion
how do electrons occupy orbitals
orbitals shown as boxes/lines and electrons as arrows
two electrons per orbital
electrons must have OPPOSITE SPINS
obey Hund’s Law
Hund’s Law
wherever possible, electrons occupy orbitals singly due to like charge repulsion
they only pair up when forced to (more e⁻ present than can be held individually)
SPIN PAIRING: electrons in the same orbital have opposite spins
maximum number of electrons in an energy level
why is this relevant
2n²
where n=principal energy level
it means some period three (/4/5/6) elements can ‘expand the octet’ to fit more electrons
