Question

Write the electron configuration for phosphorus. 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 of phosphorus (atomic number 15) is \(1s^2 2s^2 2p^6 3s^2 3p^3\). It has 5 valence electrons (in the third energy level: \(3s^2 3p^3\)) and 10 nonvalence (core) electrons (\(1s^2 2s^2 2p^6\)). The important difference in chemical reactivity is that valence electrons participate in chemical reactions and bond formation, determining an element's chemical properties, while nonvalence electrons do not directly participate.

Step-by-step solution

Write the electron configuration

The electron configuration of an element is the distribution of its electrons among the atomic orbitals, following the Aufbau principle, Pauli Exclusion principle, and Hund's rule. For phosphorus, which has an atomic number of 15, the electron configuration is: 1s² 2s² 2p⁶ 3s² 3p³

Identify valence electrons

Valence electrons are the electrons in the outermost energy level (shell) of an atom. For phosphorus, the outermost shell is the third energy level (n=3). Therefore, the valence electrons are: 3s² 3p³ Phosphorus has a total of 5 valence electrons.

Identify nonvalence electrons

Nonvalence electrons, also known as core electrons, are the electrons located in the inner energy levels (shells) of an atom. For phosphorus, the core electrons are: 1s² 2s² 2p⁶ Phosphorus has a total of 10 nonvalence electrons.

Explain the importance of valence and nonvalence electrons in chemical reactivity

The important difference between valence and nonvalence electrons in terms of chemical reactivity is that valence electrons are involved in chemical reactions and bond formation with other atoms, whereas nonvalence electrons do not participate in chemical reactions directly. Valence electrons determine the chemical properties of an element, as they are responsible for the attractive forces between atoms when forming bonds. In the case of phosphorus, its 5 valence electrons make it capable of forming 5 covalent bonds with other atoms, depending on the element it reacts with, and these bonds ultimately determine the reactivity and properties of the resulting compounds.