Question

1. beryllium (be)

electron configuration:
noble gas configuration:

1. silicon (si)

electron configuration:
noble gas configuration:

1. calcium (ca)

electron configuration:
noble gas configuration:

Explanation:

Step1: Recall electron - filling rules

Electrons fill orbitals in order of increasing energy (1s < 2s < 2p < 3s < 3p < 4s < 3d etc.), with a maximum of 2 electrons per orbital and following Hund's rule and Pauli - exclusion principle.

Step2: Determine electron configuration of Beryllium

Beryllium has 4 electrons. The electron configuration is $1s^{2}2s^{2}$. The noble - gas before Be is He (2 electrons), so the noble - gas configuration is $[He]2s^{2}$.

Step3: Determine electron configuration of Silicon

Silicon has 14 electrons. The electron configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{2}$. The noble - gas before Si is Ne (10 electrons), so the noble - gas configuration is $[Ne]3s^{2}3p^{2}$.

Step4: Determine electron configuration of Calcium

Calcium has 20 electrons. The electron configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}$. The noble - gas before Ca is Ar (18 electrons), so the noble - gas configuration is $[Ar]4s^{2}$.

Answer:

1. Electron Configuration: $1s^{2}2s^{2}$; Noble Gas Configuration: $[He]2s^{2}$
2. Electron Configuration: $1s^{2}2s^{2}2p^{6}3s^{2}3p^{2}$; Noble Gas Configuration: $[Ne]3s^{2}3p^{2}$
3. Electron Configuration: $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}$; Noble Gas Configuration: $[Ar]4s^{2}$