Question
Magnesium and sodium are both alkali metals in Period 3.
Table 2 below lists some of their physical and chemical properties.
Table 2
Property
Electron
Atomic
arrangement radius pm
Melting
point °c
Density
g/cm3
magnesium
2,8,2
173
650
1.74
sodium
2,8,1
227
98
0.97
Reactivity with water
very slow reaction
few bubbles seen
produces an alkaline
solution
vigorous reaction
lots of bubbles seen
produces an alkaline
solution
Compare the properties of magnesium and sodium and, using the information provided, explain why
magnesium is much less reactive than sodium.
[6 marks]
Answer
Magnesium has a smaller atomic radius and a higher ionization energy than sodium. This means that it requires more energy to remove an electron from magnesium and its outer electrons are held more tightly. As a result, magnesium is less likely to react with water or other substances compared to sodium. Additionally, the electron configuration of magnesium has a full outer shell, making it more stable and less likely to react. Therefore, magnesium is much less reactive than sodium.