Question

Write the electron configuration for silicon. Identify the valence electrons in this configuration and the nonvalence electrons. From the standpoint of chemical reactivity, what is the important difference between them?

Short answer

The electron configuration for silicon is \(1s^2 2s^2 2p^6 3s^2 3p^2\). Silicon has 4 valence electrons in the \(3s^2\) and \(3p^2\) orbitals and 10 nonvalence electrons in the \(1s^2\), \(2s^2\), and \(2p^6\) orbitals. Valence electrons are responsible for an atom's chemical reactivity because they are the ones involved in chemical bonding and reactions. In contrast, nonvalence electrons are closer to the nucleus and more strongly attracted by the positive charge of protons, making them less involved in chemical reactivity.

Step-by-step solution

Write the electron configuration for silicon

First, we need to find silicon's atomic number and learn how many electrons it has. Silicon has an atomic number of 14, which means it has 14 electrons. The electron configuration follows the order of electron filling in atomic orbitals, abiding by the Aufbau principle, the Pauli exclusion principle, and Hund's rule. The electron configuration for silicon is: \[1s^2 2s^2 2p^6 3s^2 3p^2\]

Identify the valence electrons and nonvalence electrons

Valence electrons are the electrons in the outermost energy level of an atom. In silicon's case, the outermost energy level is the third energy level, which contains \(3s^2\) and \(3p^2\). Therefore, silicon has 4 valence electrons as 2 electrons are contained in the 3s orbital and 2 electrons are contained in the 3p orbital. The rest of the electrons are nonvalence electrons, which are in the inner energy levels. Silicon has 10 nonvalence electrons found in the \(1s^2\), \(2s^2\), and \(2p^6\) orbitals: 1st energy level: \(1s^2\) (2 nonvalence electrons) 2nd energy level: \(2s^2 2p^6\) (8 nonvalence electrons)

Explain the chemical reactivity difference between valence and nonvalence electrons

Valence electrons are responsible for an atom's chemical reactivity because they are the ones involved in chemical bonding, ion formation, and other chemical reactions. The difference in chemical reactivity between valence and nonvalence electrons lies in their position within the atom and energy levels. Nonvalence electrons are closer to the nucleus and in lower energy levels, making them more strongly attracted by the positive charge of the protons in the nucleus. Due to their strong attraction to the nucleus, nonvalence electrons are not as involved in chemical reactivity compared to valence electrons. In contrast, valence electrons are in higher energy levels and are less tightly bound to the nucleus, which makes them more likely to participate in interactions with other atoms. This ability to participate in interactions is what makes valence electrons more important for determining chemical reactivity.

Key concepts

Valence Electrons

Valence electrons are of paramount importance when studying the chemical properties of elements. In the case of silicon, with the electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^2\), its valence electrons are the ones in the highest energy level, namely the third level with \(3s^2 3p^2\). Thus, silicon possesses four valence electrons.

These electrons play a crucial role because they can be gained, lost, or shared to form chemical bonds. In essence, the valence electrons are the 'social butterflies' of the atom, interacting with other atoms to create compounds.

Understanding which are the valence electrons within an element’s electron configuration is vital for predicting how an element will behave in reactions. For instance, elements in the same group of the periodic table have similar valence electron configurations, resulting in comparable chemical properties.

Chemical Reactivity

Chemical reactivity describes how readily an element will undergo a chemical change, which is largely influenced by the arrangement of its electrons, especially the valence electrons. As seen with silicon, the four valence electrons are the primary contributors to its chemical reactivity.

Role of Valence Electrons in Reactivity

These electrons are situated farther from the nucleus, making them more accessible for interactions. Since they are less tightly held by the nucleus's attraction, valence electrons can easily participate in bonding and reaction processes.

When elements react, their valence electrons are front and center in the process – they can be transferred to other atoms during ionic bond formations or shared in covalent bonds. This attribute is what differentiates valence electrons from the core or nonvalence electrons with respect to reactivity.

Atomic Orbitals

Atomic orbitals are regions around the nucleus of an atom where electrons are most likely to be found. The electron configuration for silicon illustrates the various orbitals occupied by electrons, such as \(1s\), \(2s\), \(2p\), \(3s\), and \(3p\).

Shapes and Energies

Each type of orbital – s, p, d, f – has a different shape and energy level. The s orbitals are spherical, while the p orbitals are dumbbell-shaped. Orbitals located at higher principle energy levels (\(n\)) have higher energy and can hold valence electrons, which are less tightly bound to the nucleus.

These shapes and energies affect how electrons within these orbitals interact with one another and with external fields. As a result, the concept of atomic orbitals is not only fundamental for determining electron configurations but also for predicting the spatial distribution and chemical behavior of electrons during bonding.