Atomic structure Flashcards
Explain why the second ionisation energy of sodium is greater than the second ionisation energy of magnesium: MS [3]
Na2+ has an electron lost from a 2p orbital
Mg2+ requires a loss of electron from a 3s orbital
There is less shielding in Na
State the meaning of the term first ionisation energy: MS [2]
Enthalpy needed to remove one mole of electrons from one mole of atoms in a gaseous state
Explain why the value of the first ionisation energy of sulfur is less than the value of the first ionisation energy of phosphorus: MS [2]
Paired electrons in the 3p orbital
Repel
State the element in Period 3 that has the highest first ionisation energy. Explain your answer: MS [3]
- Argon
- Largest number of protons and the highest nuclear charge
- There is the same amount of shielding
State the element in Period 3 that has the highest melting point. Explain your answer: MS [3]
- Silicon
- Giant covalent lattice structure with strong covalent bonds
- Lots of them have to be broken which requires a lot of energy to achieve
State and explain the trend in the first ionisation energies of the elements in Group 2 from magnesium to barium: MS [3]
- Decrease
- Ions get bigger with more shells
- Weaker attraction of the ion to the lost electron
Why is the Bohr model not fully correct?
- The lecterns in each shell have slightly different energies
- The model now includes sub-shells
- These explain experimental ionisation energy trends
How did Niels Bohr develop Rutherford’s nuclear model further?
- He proposed that electrons existed in shells
- These were orbits with fixed energy
- When the electrons moved between shells, electromagnetic radiation with a fixed energy was emitted or absorbed
- This made sense of experimental data that detected radiation
What atomic model was developed after the gold foil experiment?
- The nuclear model of the atom
- A tiny positively charged nucleus
Surrounded by a cloud of negative electrons - Most of the atom was empty space
What was J.J. Thomson’s atomic model?
Plum pudding model
What was John Dalton’s model of the atom at the start fo the 19th century?
He said solid spheres made up different elements
What element has the highest second ionisation energy?
Lithium - it’s first electron would be removed from the 2s shell. it’s second electron is removed from the 1st shell, closest to the nucleus, which has no shielding effects from inner shells. It has a bigger second ionsation energy than He due to a higher nuclear charge.
Why is there a small drop from P to S in ionisation energy?
With sulphur there are 4 electrons in the 3p sub shell and the 4th is starting to doubly fill the first 3p orbital. When the second electron is added to a 3p orbital there is a slight repulsion between the two negatively charged electrons which makes the second electron easier to remove
Why is there a small drop from Mg to Al in 1st i.e?
Al is starting to fill a 3p sub shell, whereas Mg has its outer electrons in the 3s sub shell. The electrons in the 3p subshell are slightly easier to remove because the 3p electrons are higher in energy and are also slightly shielded by the 3s electrons
Why has Na got a much lower first ionisation energy than Neon?
This is because Na will have its outer electron in a 3s shell further from the nucleus and is more shielded. So Na’s outer electron is easier to remove and has a lower ionisation energy.
Why is there a general increase in first ionisation energy across a period?
As one goes across a period the electrons are being added to the same shell which has the same distance from the nucleus and same shielding effect. The number of protons increases, however, making the effective attraction of the nucleus greater.
Why has Helium have the largest first ionisation energy?
Its first electron is in the first shell closest to the nucleus and has no shielding effects from inner shells. He has a bigger first ionisation energy than H as it has one more proton
Define second ionsation energy
The energy required to remove 1 mol of electrons from 1 mole of gaseous ions with a single positive charge
Define first ionisation energy
The first ionisation energy is the energy required to remove 1 mole of electrons from 1 mole of gaseous atoms
What’s important to note about the electronic structure of d-block ions?
They lose 4s electrons before their 3d electrons
What do we mean by molecular ion / parent ion?
The largest peak.This is when the complete molecule passes through the mass spectrometer - it has the largest m/z and will be equal to the relative molecular mass.
What can happen to molecules during an electron impact ionisation stage? What will this show on the mass spectra?
Molecules will often break up and give a series of peaks caused by the fragments.
Describe Detection
Assuming they have the same charge, lighter ions will reach the detector first. When these positive ions hit the detection plate, they gain an electron, producing a flow of charge. The greater the abundance, the greater the current produced.
