The table shows the first five ionisation energies of element X.
| Element | Ionisation energy / \(\mathrm{kJ\,mol^{-1}}\) | ||||
|---|---|---|---|---|---|
| 1st | 2nd | 3rd | 4th | 5th | |
| X | 736 | 1450 | 7740 | 10500 | 13600 |
Element X is in Period 3 of the Periodic Table.
What is element X?
Correct Answer: \( \boxed{\mathrm{B}} \)
There is a very large increase between the second and third ionisation energies:
\(1450 \rightarrow 7740\,\mathrm{kJ\,mol^{-1}}\)
This shows that two outer-shell electrons are removed easily before an electron from an inner shell is removed.
Therefore, element X has two valence electrons and belongs to Group 2.
The Period 3 Group 2 element is magnesium.
Therefore, the correct answer is (B).
Which equation has an energy change that is equal to the first ionisation energy of bromine?
Correct Answer: \( \boxed{\mathrm{A}} \)
The first ionisation energy is the energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous \(1+\) ions.
It is represented by:
\(\mathrm{Br(g)\rightarrow Br^+(g)+e^-}\)
Options (C) and (D) begin with bromine molecules rather than gaseous atoms, while option (B) represents electron gain instead of electron removal.
Therefore, the correct answer is (A).
The data in the table gives the 5th to the 10th ionisation energies of three elements from Period 3 of the Periodic Table.
| Element | Ionisation energy / \(\mathrm{kJ\,mol^{-1}}\) | |||||
|---|---|---|---|---|---|---|
| 5th | 6th | 7th | 8th | 9th | 10th | |
| X | 6274 | 21269 | 25398 | 29855 | 35868 | 40960 |
| Y | 7012 | 8496 | 27107 | 31671 | 36579 | 43140 |
| Z | 6542 | 9362 | 11018 | 33606 | 38601 | 43963 |
What are the correct identities of these three elements?
| Element X | Element Y | Element Z | |
|---|---|---|---|
| A | Na | Mg | Al |
| B | Mg | Al | Si |
| C | P | S | Cl |
| D | S | Cl | Ar |
Correct Answer: \( \boxed{\mathrm{C}} \)
A large jump in successive ionisation energies occurs when all valence electrons have been removed and an inner-shell electron is removed.
Therefore, the correct answer is (C).
