Q.Ge (belongs to period 4 and group 14)

Step 1. Note the period and group. Ge is in period 4 (so its outermost shell has n=4) and group 14 (general outer configuration $ns^2np^2$, per Table 7.1/Table 7.6).

Step 2. Build up the configuration. Following the Aufbau order through period 4 (section 7.3.1): $[Ar]4s^2$ (K, Ca) → $[Ar]4s^23d^{1-10}$ (Sc to Zn, filling the d-block) → $[Ar]4s^23d^{10}4p^{1-6}$ (Ga to Kr, filling the p-block). Ge is the third p-block element of period 4, so its p subshell holds 2 electrons.

Step 3. Write the full configuration. $Ge: [Ar]4s^23d^{10}4p^2$, i.e. $1s^22s^22p^63s^23p^64s^23d^{10}4p^2$.

Step 4. Identify the outer/valence part. The outer (valence-shell) part relevant to group 14's $ns^2np^2$ pattern is $4s^24p^2$; the $3d^{10}$ is a completely-filled inner subshell.

Building the configuration via period-4 Aufbau order and confirming against the group-14 general pattern

• Forgetting to include the completely-filled inner $3d^{10}$ subshell that lies between 4s and 4p in period 4.
• Writing the outer pattern as $ns^2np^4$ (group 16's pattern) instead of $ns^2np^2$ by miscounting group 14's valence electrons.