✅1 - Atomic Structure and the Periodic Table Flashcards
What are the subatomic particles in an atom?
Neutron, Proton and Electron
What is the relative charge of a neutron?
+
What is the relative charge of a proton?
0
What is the relative charge of a electron?
-
What is the atomic (proton) number?
The number of protons in the nucleus
What is the atomic mass number?
The number of protons + neutrons, also the relative atom mass
What are isotopes?
Atoms of the same element with different number of neutrons, but the same number of protons and electrons
What is relative atomic mass?
The weighted mean mass of an atom of an element relative to 1/12th of the mass of Carbon12
What is relative isotopic mass?
The mass of an isotope relative to 1/12th of the mass of Carbon12
What does a mass spectrometer measure?
The masses of atoms and molecules (as well as the fragments that make up the molecule)
What are Molecular Ion Peaks (M+) used to determine?
An exact Relative Molecular Mass
What peak is the M+?
The strongest peak furthest to the right
When should the term ‘Relative Formula Mass’ be used?
For compounds with giant structures
In a Mass Spectrum of an element, what does the number of peaks show?
The number of isotopes
In a Mass Spectrum of an element, what does the M/z of a peak show?
The mass number of the isotope
In a Mass Spectrum of an element, what does the size of a peak show?
The relative abundance of an isotope
What are the 4 processes in a mass spectrometer?
Ionisation, Acceleration, Deflection and Detection
Why must a vacuum be used in a mass spectrometer?
- It means no interference from atoms or molecules in air
- Molecular fragments could not exist otherwise
What is M/z?
Mass to charge ration, mass divided by charge
What does the position of an atom on the Mass Spectra depend on?
The amount of deflection, therefore the mass of the atom.
What are quantum shells?
Defined energy levels, filled from the inside out
What are orbitals?
Subshells of the quantum shells, where electrons exist , a pattern of electron density
What shape is the S orbital?
Spherical
How many electrons can an S orbital hold?
2, with a 90% probability of finding them in its boundary
What shape are P orbitals?
‘Dumbbell’ shape
What are the names of the 3 P orbitals?
Px, Py ad Pz
How many electrons can the P orbitals hold in total?
6
Why is the 4s orbital filled before the 3d orbital?
Because it is slightly lower in energy
How many electrons do the D orbitals hold in total?
10
How many electrons fill the first quantum shell?
2
How many electrons fill the second quantum shell?
8
How many electrons fill the third quantum shell?
18
How many electrons fill the fourth quantum shell?
32
Two electrons in the same orbital must have opposite…
…spins
In what order do electrons fill subshells?
First singly, then pairing up in opposite spins
What does electronic configuration determine?
The chemical properties of an element
What provides evidence for the existence of quantum shells?
Atomic Emission Spectra
What provides evidence for the existence of quantum shells AND the group to which the element belongs?
Successive Ionisation Energies
What provides evidence for electron subshells?
First Ionisation Energies
If an electron takes in energy from its surroundings it is…
…excited to a higher energy level
When an electron drops down tot a lower energy level, it…
…releases this energy in the form of a photon with energy matching the gap.
When do the energy levels get closer together?
As energy/frequency increases
What suggests that electrons exist at very specific energy levels?
There is no ‘inbetween’ amount of energy, electrons exist at very specific energy levels
What is ‘first ionisation energy’?
The energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form one mole of gaseous 1+ ions
What is the equation for the first ionisation energy for sodium?
Na(g) —–> Na+(g) + e-
Why does Atomic Radius affect the First Ionisation Energy?
The more shells and atom has, and therefore the further away the outer electrons are from the nucleus, the less attraction they experience
Why does Nuclear Charge affect the First Ionisation Energy?
The more protons, the greater the nuclear charge, and the greater the attraction felt bu the electrons
Why does Electron Shielding affect the First Ionisation Energy?
As the number of electrons between the outer electrons and the nucleus increases, the outer electrons feel less attraction towards the nucleus
What happens to first ionisation energies going down a group?
It decreases
What happens to first ionisation energies going across a period?
They generally increase
What happens to first ionisation energies between Groups 5 + 6, and why?
it decreases, because grp 6 elements have a paired electrons in one of their p orbital cousing an electron-electron repulsion which decrease ionisation energy
What happens to first ionisation energies between Groups 2 + 3, and why?
decreases, because grp 3’s outer electron is in the p orbital which has further from nucleus than s orbital hence easier to remove.
What trends are there in the periodic table?
- melting and boiling points
- atomic radius
- ionisation energies
Why do metallic bonds get stronger across the metals?
Because there are more electrons per positive ion (2+ charge means there’s 2 delocalised electrons for each positive ion
How does atomic radius change across a period?
It decreases, because as the nuclear charge of the atom increases, the outer shells are pulled inwards
How does electron shielding change across a period?
It doesn’t, because they’re still filling the same quantum shell
How does nuclear charge change across a period?
It increases, because the number of protons increases
How do melting/boiling points change across a period?
Increase from Groups 1 to 3 (stronger metallic bonding).
Peak at Group 4 (giant covalent structures). e.g. silicon
Decrease from Groups 5 to 8 (weaker van der Waals forces).
Lowest in Group 8 (noble gases with weak intermolecular forces).
