Question

Determine the number of valence electrons in each element. Which elements do you expect to lose electrons in chemical reactions? Which do you expect to gain electrons? $$\text { a. } \mathrm{Al}\quad \text { b. } \mathrm{Sn} \quad \text { c. Br } \quad \text { d. } \mathrm{Se}$$

Short answer

Al has 3, Sn has 4, Br has 7, and Se has 6 valence electrons. Al and Sn are expected to lose electrons, while Br and Se are expected to gain electrons.

Step-by-step solution

Determine Valence Electrons (Aluminum - Al)

Refer to the periodic table to find Aluminum (Al). It is in group 13, thus it has 3 valence electrons.

Determine Valence Electrons (Tin - Sn)

Look up Tin (Sn) in the periodic table. Tin is in group 14, indicating it has 4 valence electrons.

Determine Valence Electrons (Bromine - Br)

Find Bromine (Br) on the periodic table. Bromine belongs to group 17, which means it has 7 valence electrons.

Determine Valence Electrons (Selenium - Se)

Identify Selenium (Se) in the periodic table. Selenium is a member of group 16, thereby having 6 valence electrons.

Predict Electron Transfer for Aluminum (Al)

Given its 3 valence electrons, Aluminum (Al) is likely to lose electrons during chemical reactions to achieve a stable octet, forming a +3 charge.

Predict Electron Transfer for Tin (Sn)

Since Tin (Sn) has 4 valence electrons, it tends to lose electrons in chemical reactions, aiming for a stable electronic configuration, possibly forming a +2 or +4 charge.

Predict Electron Transfer for Bromine (Br)

Bromine (Br), with its 7 valence electrons, will typically gain one electron in chemical reactions, to complete its octet, resulting in a -1 charge.

Predict Electron Transfer for Selenium (Se)

Selenium (Se) is prone to gain 2 electrons during chemical reactions to fill its valence shell, leading to a -2 charge.

Key concepts

Periodic Table Groups

Understanding the periodic table is essential for grasping the behaviors of elements, especially their valence electrons. Valence electrons are the electrons in the outermost shell of an atom and play a pivotal role in chemical reactions.

Elements are arranged in the periodic table into 18 vertical columns known as groups. These groups indicate the number of valence electrons in the atoms of the elements. For instance, elements in group 1 have one valence electron, while those in group 18 have eight, with the exception of helium, which has two. Elements like Aluminum (Al), which is in group 13, displays three valence electrons, leading to specific chemical properties and reactivity.

Electron Transfer

Electron transfer is a fundamental process in chemical reactions. Atoms seek to achieve a stable electronic configuration, which often resembles the nearest noble gas arrangement. This is typically done through the loss or gain of electrons.

Metals, generally found on the left side of the periodic table, are more inclined to lose electrons and form positive ions, known as cations. Nonmetals, situated on the right side of the periodic table, often gain electrons to form negative ions, called anions. For example, Tin (Sn) from group 14, tends to lose electrons, while Bromine (Br) from group 17 tends to gain electrons, following this trend.

Chemical Reactions

Chemical reactions involve the rearrangement of atoms or ions to form new substances. These reactions are driven by the interactions between valence electrons, as elements strive to achieve a more stable electron configuration.

Reactions such as oxidation and reduction are clear examples of electron transfer processes. Oxidation involves losing electrons whereas reduction involves gaining electrons. Considering the elements from the exercise, Aluminum (Al) is likely to oxidize, whereas Bromine (Br) and Selenium (Se) are likely to reduce in reaction scenarios.

Stable Octet Rule

The stable octet rule is a chemical rule of thumb which states that atoms are most stable when they have eight electrons in their valence shell. This rule applies to most elements, excluding hydrogen and helium whose stable configuration is two valence electrons.

Consequently, elements that do not have a full octet of electrons in their valence shell will tend to lose, gain, or share electrons to achieve stability. Tin (Sn), with four valence electrons, will lose electrons to move towards this stable configuration, whereas Bromine (Br) will gain an electron to complete its octet.