Complete the table so that the composition and identity of some atoms and ions are shown.
The fifth to eighth ionisation energies for three elements in the third period of the Periodic Table are shown. The symbols used as references are not the real symbols of the elements.
State and explain the group number for element Y.
State and explain the overall trend in first ionisation energies across the third period.
Complete the electronic configuration of element X: $1s^2 \,\ldots$
A sample of oxygen contains a mixture of three isotopes. The table provides information for two of these isotopes.
Calculate the abundance of the third isotope.
The relative atomic mass of this oxygen sample is $16.0044$. Calculate the mass number of the third isotope. You must show your working.