Question

Consider the element silicon, Si. (a) Write its electron configuration. (b) How many valence electrons does a silicon atom have? (c) Which subshells hold the valence electrons?

Short answer

The electron configuration of Silicon (Si) is \(\mathrm{1s^2 2s^2 2p^6 3s^2 3p^2}\). Silicon has 4 valence electrons, which are found in the 3s and 3p subshells.

Step-by-step solution

Writing the electron configuration of Silicon (Si)

Silicon is the element with atomic number 14, which means it has 14 electrons. To write its electron configuration, we can follow the Aufbau principle, which suggests filling the orbitals in the order of increasing energy levels. The order is as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 4f, 5d, 6s, 5f, 6d, 7s, 6f, 7d, 7f, 8s, ... Filling in each orbital with the given 14 electrons, we get: 1s², 2s², 2p⁶, 3s², 3p² So, the electron configuration for Silicon is \(\mathrm{1s^2 2s^2 2p^6 3s^2 3p^2}\).

Determining the number of valence electrons

Valence electrons are the electrons found in the outermost energy level of an atom. In the case of Silicon, the outermost energy level is n=3. We have 2 electrons in the 3s subshell and 2 electrons in the 3p subshell. Therefore, Silicon has a total of 2 + 2 = 4 valence electrons.

Identifying the subshells holding the valence electrons

As mentioned in Step 2, the valence electrons are in the outermost energy level, which is n=3 for Silicon. These valence electrons are found in two subshells: the 3s subshell and the 3p subshell. So, the subshells that hold the valence electrons of Silicon are 3s and 3p.