Valence Electrons

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Valence Electrons

This lesson aligns with NGSS PS1.A

Introduction

Electrons are subatomic particles that are found outside the nucleus of an atom. The charge of an electron is considered to be -1 elementary charge. Moreover, this charge is equal in magnitude to the charge held by protons but has an opposite sign. Valence electrons are the s and p outermost electrons in an atom. The electrons present in the inner shell are known as core electrons. When we study the atom, we come across these tiny subatomic particles- valence electrons. In this article, we will delve into the definition, characteristics, and significance of valence electrons, as well as their role in the formation of chemical compounds.

Valence Electrons

The word “Valence '' represents the number of electrons that is needed by an atom to either lose or gain so that it can attain the nearest noble gas or inert gas’s electronic configuration. These specific electrons in the outer shells that are not filled are called valence electrons.

Valence electrons are located in the outermost energy level, or shell, of an atom, that are mostly negative charged particles. These electrons are involved in the formation of chemical bonds with other atoms, determining the atom's reactivity and bonding capabilities. However, it is important to note that not all electrons are associated with the atom. Only those electrons located in the outermost shell are capable of participating in the formation of a chemical bond or a molecule. These electrons are referred to as valence electrons.

Valence electrons actively participate in chemical reactions due to their higher energy level in comparison to electrons located in inner orbits. Additionally, the count of valence electrons plays a crucial role in determining specific chemical properties of an element, including its valence or valency. Furthermore, the number of valence electrons provides information about the presence of unpaired electrons, indicating how readily the atoms engage in bonding, and how many atoms can take part.

Key Characteristics of Valence Electrons:

The number of valence electrons in an atom can be determined directly from the periodic table, as it corresponds to the group number of the atom. Atoms are considered most stable if they have filled valence electrons. Atoms must share or transfer electrons to attain a filled shell of electrons.

The number of valence electrons greatly influences an atom's reactivity. Generally, atoms with similar numbers of valence electrons exhibit similar chemical behavior. Elements in the same group of the periodic table have the same number of valence electrons, leading to comparable chemical properties.
For main group elements, the presence of valence electrons is confined to the outermost electron shell. However, for transition metals, a valence electron can be found in the inner shell.
An atom characterized by a closed shell of valence electrons tends to be chemically inert. A valence electron can either absorb or emit energy in the form of a photon.
Furthermore, valence electrons play a role in determining the electrical conductivity of an element, categorizing it as either a metal, non-metal, or metalloid.

Lewis Dot Structures:

Valence electrons are often represented using Lewis dot structures, a notation that illustrates the number of valence electrons around an atom. This visual representation simplifies the understanding of how atoms combine to form molecules by showcasing the sharing or transfer of valence electrons.

For instance, the valence electrons of Sodium, Magnesium and Chlorine are shown below;

Significance of Valence Electrons

Predicting Chemical Reactivity:

The number of valence electrons directly correlates with an element's reactivity. Elements with a filled shell of valence electrons, achieving a stable electron configuration, are less reactive. While those with incomplete valence electron shells are more likely to form bonds to attain stability.

Chemical Bonding:

The interaction between the valence electrons of different atoms determines the type of bond formed. Whether it be a strong covalent bond where electrons are shared or an ionic bond involving the transfer of electrons.

Periodic Trends:

The periodic table organizes elements based on their atomic number and electron configuration, providing a systematic way to understand the trends in chemical properties. Elements within the same group exhibit similar valence electron configurations, leading to analogous chemical behaviors.

Summary

Valence electrons are located in the outermost energy level, or shell, of an atom, that are mostly negative charged particles.
Elements in the same group of the periodic table have the same number of valence electrons.
For main group elements, the presence of valence electrons is confined to the outermost electron shell.
For transition metals, a valence electron can be found in the inner shell.
Valence electrons are often represented using Lewis dot structures, a notation that illustrates the number of valence electrons around an atom.

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