Question

Which atom has a larger atomic radius, magnesium (Mg) or silicon (Si)? Explain your reasoning using shielding and core charge.

Options:
A) Magnesium (Mg) - Due to fewer electron shells and less shielding.
B) Silicon (Si) - Due to a higher atomic number and greater core charge.
C) Magnesium (Mg) - Due to a higher atomic number and greater core charge.
D) Silicon (Si) - Due to fewer electron shells and less shielding.

Answer 1

Magnesium (Mg) has a larger atomic radius than silicon (Si) due to having fewer electron shells and experiencing less effective nuclear charge, resulting in less pull on the valence electrons and a larger atomic radius.

Step-by-step explanation:

The atom that has a larger atomic radius between magnesium (Mg) and silicon (Si) is magnesium (Mg). This is because atomic radius generally decreases as we move from left to right across a period. Magnesium is in the second group of the periodic table, while silicon is in the fourteenth group. As we move across the period from magnesium to silicon, the number of protons in the nucleus increases, which means the core charge increases. However, the shielding effect only increases slightly because the added electrons are in the same principal quantum number shell, and do not shield as effectively as core electrons would.

This results in a higher effective nuclear charge (Zeff) for silicon, which draws the electrons closer to the nucleus and decreases the atomic radius. Therefore, magnesium with fewer protons has a smaller effective nuclear charge and less pull on its valence electrons, resulting in a larger atomic radius. The correct option is: A) Magnesium (Mg) - Due to fewer electron shells and less shielding.