Problem 16 - Chemistry The Central Science In Si Units

Question

(a) Use Lewis symbols to represent the reaction that occurs between Li and O atoms. (b) What is the chemical formula of the most likely product? (c) How many electrons are transferred? (d) Which atom loses electrons in the reaction?

Step-by-Step Solution

Answer

(a) Represented with Lewis symbols: Li⋅ + 2⋅O: → Li2O. (b) Chemical formula is Li2O. (c) Two electrons are transferred. (d) Lithium loses electrons.

Step 1: Understanding Lewis Symbols

Lewis symbols represent the valence electrons of an atom. Lithium (Li) has one valence electron (since it's in Group 1) represented as 'Li⋅', whereas oxygen (O) has six valence electrons (as it is in Group 16) represented as '⋅O:'. Oxygen needs two more electrons to achieve a full octet.

Step 2: Electron Transfer Analysis

Lithium tends to lose its one valence electron to achieve a stable configuration, and oxygen tends to gain electrons to fill its octet. For the reaction between Li and O, each oxygen atom will gain two electrons. Therefore, two lithium atoms are needed to provide two electrons to one oxygen atom.

Step 3: Determine the Chemical Formula

Since each oxygen atom will gain two electrons and each lithium atom can only donate one electron, we need two Li atoms to satisfy the electron need of one O atom. The chemical formula will be Li2O, which shows that two lithium atoms react with one oxygen atom.

Step 4: Counting Electron Transfer

In this reaction, two electrons in total are transferred; each of the two lithium atoms donates one electron to the oxygen atom.

Step 5: Identifying the Electron Donor

Lithium is the atom that loses electrons in this reaction. Each lithium atom donates its one valence electron to the oxygen atom.

Key Concepts

Electron Transfer

In a chemical reaction between lithium (Li) and oxygen (O), we witness an important process known as electron transfer. This is key to forming stable compounds. Electron transfer involves the movement of electrons from one atom to another.
In our scenario, lithium donates electrons, while oxygen accepts them. This exchange is driven by the tendency of both elements to achieve a more stable electron configuration. Lithium, found in Group 1 of the periodic table, prefers to lose one valence electron to resemble the stable electron configuration of a noble gas. Oxygen, on the other hand, in Group 16, aims to gain electrons to complete its outer shell with eight electrons, a condition known as the octet rule.

• Each oxygen atom requires two electrons to complete its octet.
• Each lithium atom can donate one electron.
• Thus, one oxygen atom necessitates the transfer of two electrons, requiring two lithium atoms to participate in the exchange.

This electron transfer forms the basis of ionic bonds between lithium and oxygen, resulting in the formation of a stable ionic compound.

Chemical Formula

The chemical formula represents the ratio of atoms in a compound and is crucial for understanding its composition. For the reaction between lithium and oxygen, the most likely product is given by the formula Li extsubscript{2}O. This shows that two lithium atoms bond with one oxygen atom.
To determine this, we consider the need of each element to exchange electrons:

• Oxygen needs two electrons to complete its stable octet.
• Each lithium atom can lose one electron.
• Therefore, two lithium atoms are required to provide the necessary electrons for one oxygen atom.

This results in two positively charged lithium ions (Li extsuperscript{+}) and one negatively charged oxide ion (O extsuperscript{2-}), which together compose the neutral compound Li extsubscript{2}O.
The subscript "2" in Li extsubscript{2}O indicates the number of lithium atoms involved in balancing the charge from one oxygen atom in the compound, showcasing the stoichiometry necessary to maintain charge neutrality in the compound.

Valence Electrons

Valence electrons play a crucial role in chemical bonding and reactions. Understanding them is key to predicting how elements will react. They are the electrons present in the outermost shell of an atom.
In the periodic table, the group number can often help determine the number of valence electrons for an element:

• Lithium (Li) is in Group 1, with one valence electron.
• Oxygen (O) is in Group 16, possessing six valence electrons.

The behavior of valence electrons affects how atoms like lithium and oxygen interact. Lithium aims to lose its single valence electron to achieve a noble gas-like stable configuration. Oxygen, with six valence electrons, desires to gain two additional electrons to complete its octet.
This drive for stability through gaining or losing valence electrons is why lithium transfers its electron to oxygen during a chemical reaction, leading to the formation of lithium oxide (Li extsubscript{2}O) through ionic bonding.