Question

1. when si became the si⁴⁺ ion, did it grow or shrink? which is bigger — sis atomic radius, or si⁴⁺s ionic radius?

Explanation:

Step1: Analyze electron change

Silicon (Si) has an atomic number of 14, with electron configuration $1s^2 2s^2 2p^6 3s^2 3p^2$. When it forms $\text{Si}^{4+}$, it loses 4 electrons (from the 3s and 3p subshells), resulting in an electron configuration of $1s^2 2s^2 2p^6$.

Step2: Relate electron loss to radius change

Losing electrons removes the outermost energy level (the 3rd level here). Also, with fewer electrons, the remaining electrons experience a greater effective nuclear charge (since there are fewer electrons to shield the positive charge of the nucleus), pulling them closer to the nucleus. So the ion shrinks.

Step3: Compare atomic and ionic radii

Since $\text{Si}^{4+}$ has a smaller electron cloud (due to lost electrons and increased effective nuclear charge) than neutral Si, Si's atomic radius is bigger than $\text{Si}^{4+}$'s ionic radius.

Answer:

When Si becomes $\text{Si}^{4+}$, it shrinks. Si's atomic radius is bigger than $\text{Si}^{4+}$'s ionic radius.