3.1.1 Atomic structure Flashcards
Nucleons
Nucleons are protons and neutrons in the nucleus.
Position of protons
Nucleus
Relative mass of a proton
1
Relative charge of a proton
+1
Position of neutrons
Nucleus
Relative mass of a neutron
1
Relative charge of a neutron
0
Position of electrons
Orbitals
Relative mass of an electron
1/1800
Relative charge of an electron
-1
Mass number
Sum of protons and neutrons
Atomic number
The amount of protons in the nucleus
Number of neutrons is worked out by…
Subtracting the atomic number from the mass number
Isotopes
Atoms of the same element with the same number of protons but a different amount of neutrons
Isotopes have similar chemical properties because…
they have the same electron configuration
Isotopes have varying physical properties because…
they have different masses
Ions
A charged particle formed when an atom or molecule gains
or loses one or more electrons
Relative Isotopic Mass
The mass of an atom of a particular isotope compared to 1/12
the mass of an atom of carbon-12
Relative Atomic Mass (Ar)
The average mass of an atom compared to 1/12 the mass of
an atom of carbon-12
Relative Molecular Mass (Mr)
The average mass of a molecule compared to 1/12 the mass
of an atom of carbon-12
Mass Spectrometer: Why is it kept in vacuum conditions?
To prevents the ions produced colliding with molecules of air
Mass Spectrometer: What happens during ionisation?
The sample is dissolved in a volatile solvent and forced
through a fine, hollow needle which is connected to a
positive terminal of a high voltage supply. The sample is shot
with an electron gun, which knocks off an electron,
producing positively charged ions.
Mass Spectrometer: What happens during acceleration?
Positive ions are attracted to a negatively charged plate,
causing them to accelerate. Lighter ions with a higher charge
move faster
Mass Spectrometer: What happens during ion drift?
The ions pass through a hole in the negatively charged plate,
forming a beam, which drift towards the detector
Mass Spectrometer: What happens during detection?
The lighter ions which have the fastest velocities arrive at the
detector first. The positive ions pick up an electron, causing a
current to flow
Mass Spectrometer: What happens during data analysis?
Signals from the detector are passed to a computer which
generates a mass spectrum
Mass Spectrometer: What is the mass spectrometer
measuring?
M:Z ratio and abundance
How do you calculate R.A.M from a mass spectrum?
You multiply the m:z ratio and abundance together for each
peak. You then add the totals together and divide by the total
relative abundance.
What sub-level can principle level 1 hold?
1s
What sub-levels can principle level 2 hold?
2s, 2p
What sub-levels can principle level 3 hold?
3s, 3p, 3d
What sub-levels can principle level 4 hold?
4s, 4p, 4d, 4f
How many electrons can sub-level S hold?
2
How many electrons can sub-level P hold?
6
How many electrons can sub-level D hold?
10
How many electrons can sub-level F hold?
14
What shape are S sub-levels?
Spherical
What shape are P sub-levels?
Dumbbells
Why is the 3d sub-level filled after the 4s sub-level?
Because 3d is higher in energy, so 4s is filled first and then
when 3d is filled, the energy level drops to below 4s
First Ionisation Energy
The enthalpy change when one mole of gaseous atoms forms
one mole of gaseous atoms with a singe positive charge by
losing one electron
Second Ionisation Energy
The enthalpy change when one mole of gaseous ions with a
single positive charge forms one mole of gaseous ions with a
2+ charge by losing one electron
Factors affect ionisation energy: Nuclear Charge
The higher the nuclear charge (the more protons there are)
the greater the attraction of the outer electrons to the nucleus
Factors affect ionisation energy: The distance of the outer
electrons to the nucleus
The larger the atom, the further the outer electrons are away
from the nucleus, making the attraction weaker
Factors affect ionisation energy: Shielding
Electrons in the outer shell are repelled by electrons in
complete inner shells, weakening the attraction of the
nucleus
Factors affect ionisation energy: In-orbital Repulsion
Once the electrons are paired, they start repelling each other,
the degree of repulsion affects how easy it is to remove
electrons
Why are the successive ionisation energies always higher?
Because a positive ion is formed from the first ionisation
energy, meaning the nuclear attraction increases, making it
harder for the second electron to be removed
Why is He’s ionisation energy bigger than H’s?
- Increased nuclear charge (gone from + to +2)
- Same shielding
- Same distance from nucleus to outer electron
Why is there such a large drop of ionisation energy between
He and Li?
- Increased shielding (Li enters 2s orbital, He still on 1s)
- Increased nuclear charge
- Outer electrons are further away from the nucleus
Why is Be’s ionisation energy greater than Li?
-Increased nuclear charge
-Shielding same as Li
-Outer electrons are the same distance away from the nucleus
in both
Why is Be’s ionisation energy higher than B?
-Increased nuclear charge
-Increased shielding (B enters 2p orbital) so is shielded by 1s
and 2s orbitals
-Outer electrons are further away in B
Why is there a drop of ionisation energy between N and O?
- Increased nuclear charge
- Shielding same (still in 2p orbital)
- Same amount of shielding
