3.1.1 - Atomic Structure (not finished) Flashcards
What did John Dalton discover in 1803?
He theorised that there must be a smallest bit of an element
What did J.J. Thompson discover in 1904?
Electrons - randomly placed (Plum Pudding Model)
What did Ernest Rutherford discover in 1911?
The nucleus - gold leaf experiment - electrons orbit
What did Niels Bohr discover in 1913?
Electrons are arranged in shells
What did Erwin Schrodinger discover in 1926?
Quantum mechanics - orbitals
Define atomic number
The atomic number is equal to the amount of protons in the nucleus
Define mass number
The mass number is equal to the number of protons and neutrons combined
Define isotopes
Isotopes are atoms with the same number of protons but different number of neutrons
What is a Cation?
A positive ion (lost electrons)
What is an Anion?
A negative ion (gained electrons)
Define First ionisation energy
The amount of energy needed to remove one mole of electrons from a mole of atoms, in the gaseous state
What is the trend in first ionisation energies down a group?
Decreases
What is the trend in first ionisation energies across a period?
Increases
What does a mass spectrometer measure?
- Relative abundance
- Mass/charge ratio
What are the 4 steps in time-of-flight mass spectrometry?
- Ionisation
- Acceleration
- Ion drift
- Detection
What happens in electrospray ionisation?
- Sample is dissolved in a volatile solvent
- Sample is injected through a needle at a high voltage
- Sample is ionised by gaining a proton
What happens in electron-impact ionisation?
- Sample is vaporised
- High-energy electrons are fired at sample
- From an electron gun
- One electron is knocked off each particle (forming a positive ion)
What is the relative mass of an electron?
1/1840
Why do isotopes of the same element have the same chemical properties?
They have the same electron configuration
Explain the gold leaf experiment in terms of point P and point Q
- Rutherford fired He2+ ions at a sheet of gold foil/leaf
- When the He2+ ions arrived at point P, he concluded that most of the atom is empty space
- A very small number of He2+ ions were detected at point Q. He concluded that the atom must have a small, positive nucleus
Write the first ionisation energy of potassium (K)
K(g) -> K+(g) + e-
Write the second ionisation energy of silver (Ag)
Ag+ (g) -> Ag2+ (g) + e-
How does nuclear charge influence ionisation energy?
The more protons, the stronger the forces of attraction between the nucleus and the outer electron. Therefore, the amount of energy required to remove the electron is higher
How does distance from the nucleus influence ionisation energy?
The closer the electrons are to the nucleus, the stronger the forces of attraction between the nucleus and the outer electron. Therefore, the amount of energy needed to remove the electron is higher
How does shielding influence ionisation energy?
Shells with more shielding have their outer electrons blocked and repelled. This means there is a weaker force of attraction between the outer electron and nucleus so the amount of energy required to remove the electron is lower
Explain a graph showing the Ionisation Energy (IE) for Boron
- The IE increases (1-3) as each electron is being removed from a more positive ion each time
- The attraction becomes stronger as there are less electrons being attracted by the same number of protons
- The 4th electron is moved from a shell closer to the nucleus so is more strongly attracted to the nucleus and therefore requires more energy to remove
Why is the second ionisation energy of Be higher than the first?
The electron is removed from an ion that already has a positive charge
Why is Li a bigger atom than Be?
- Both atoms have the same number of shells
- They both have that same amount of shielding
- But Be has more protons
- So it attracts the outer most electron more strongly, making it smaller
Why is Li a bigger atom than He?
- More shells so more shielding
- Li has more electron shells which are further away from the nucleus
- The outer electrons are more shielded
- The outer electron is less strongly attracted to the nucleus
Why does He have the highest Ionisation Energy of all elements?
- Same shielding as H (none)
- More protons
Explain the GENERAL trend in first Ionisation Energies across a period
- The first IE will increase
- There are more protons in the nucleus
- The shielding remains the same
- So the attraction increases between the nucleus and outer electron
What is the maximum number of electrons in shell 1?
2
What is the maximum number of electrons in shell 2?
8
What is the maximum number of electrons in shell 3?
18
What is the maximum number of electrons in shell 4?
32
What shape is an s orbital?
Spherical
What shape is a p orbital?
Egg timer shaped
How many orbitals are there in:
s sub-shell?
p sub-shell?
d sub-shell?
s sub-shell = 1
p sub-shell = 3
d sub-shell = 5
What is the highest energy electron?
The outer most electron on an atom or ion - the furthest from the nucleus
What is the electron configuration for chromium?
1s2 2s2 2p6 3s2 3p6 4s1 3d5
