Problem 1 - Chemistry and Chemical Reactivity

Question

Give the periodic group number and number of valence electrons for each of the following atoms. (a) \(\mathrm{O}\) (d) \(\mathrm{Mg}\) (b) \(B\) (e) \(\mathrm{F}\) (c) \(\mathrm{Na}\) (f) \(\mathrm{S}\)

Step-by-Step Solution

Answer

(a) 'O' is in group 16 with 6 valence electrons. (d) 'Mg' is in group 2 with 2 valence electrons. (b) 'B' is in group 13 with 3 valence electrons. (e) 'F' is in group 17 with 7 valence electrons. (c) 'Na' is in group 1 with 1 valence electron. (f) 'S' is in group 16 with 6 valence electrons.

Step 1: Understanding the Periodic Table Group

The periodic table is divided into groups (columns) and periods (rows). Each element in a group typically has the same number of valence electrons, which are the electrons in the outermost shell.

Step 2: Identify Group Number for Oxygen (O)

Oxygen is in group 16 of the periodic table. Elements in group 16 have 6 valence electrons.

Step 3: Identify Group Number for Magnesium (Mg)

Magnesium is located in group 2, which is also known as the alkaline earth metals. Elements in this group have 2 valence electrons.

Step 4: Identify Group Number for Boron (B)

Boron appears in group 13 of the periodic table. Elements in group 13 have 3 valence electrons.

Step 5: Identify Group Number for Fluorine (F)

Fluorine is part of group 17, known as the halogens. Elements in group 17 have 7 valence electrons.

Step 6: Identify Group Number for Sodium (Na)

Sodium is in group 1, known as the alkali metals. Elements in this group have 1 valence electron.

Step 7: Identify Group Number for Sulfur (S)

Sulfur is found in group 16, like oxygen. Elements in group 16 have 6 valence electrons.

Key Concepts

Valence Electrons

Valence electrons are simply the electrons in the outermost shell of an atom. These electrons have a crucial role because they allow atoms to form bonds with one another.
By bonding, atoms can form molecules and compounds.
The number of valence electrons determines many properties of an atom, including how it reacts chemically with other substances. Here’s why valence electrons are important:

• They are involved in forming chemical bonds.
• They determine the reactivity and stability of an element.

To find out the number of valence electrons for an element, you can refer to the group number in the periodic table. Most main-group elements have the same number of valence electrons as their group number. For example, oxygen is in group 16 of the periodic table, which means it has 6 valence electrons.

Alkaline Earth Metals

Alkaline earth metals belong to group 2 of the periodic table. They include elements like magnesium (Mg) and calcium (Ca).
These metals are known for being quite reactive, but not as much as the alkali metals in group 1.
Alkaline earth metals have two valence electrons, which they can easily lose to form positive ions. Characteristics of Alkaline Earth Metals: - Relatively soft and low density compared to transition metals. - Shiny and silvery-white appearance. - Reactivity increases as you move down the group. Magnesium, for example, is a key ingredient in fireworks due to its bright white flame. It is crucial for many industrial processes and is also vital for human health.

Halogens

Halogens are found in group 17 of the periodic table and include elements such as fluorine (F), chlorine (Cl), and iodine (I).
These elements are highly reactive and have seven valence electrons.
Because they are just one electron short of having a full outer shell, halogens often form salts when they react with metals, seeking to gain one additional electron. Notable Traits of Halogens: - Very high electronegativity, meaning they attract electrons strongly. - Typically exist as diatomic molecules (e.g., F₂, Cl₂). - They have varied states at room temperature: fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid. Fluorine, in particular, is the most reactive of all the elements and can even react with noble gases under specific conditions.

Alkali Metals

Alkali metals are located in group 1 of the periodic table and include elements like lithium (Li), sodium (Na), and potassium (K).
These metals are incredibly reactive, even more so than the alkaline earth metals in group 2.
Alkali metals have just one valence electron, which they can lose easily, making them excellent conductors of electricity. Key Characteristics of Alkali Metals: - Very soft and can be cut with a knife. - Have low melting points compared to other metals. - React vigorously with water, producing hydrogen gas and an alkaline solution. Sodium, a well-known alkali metal, is widely used in our daily lives, most notably in the form of table salt (sodium chloride). Due to their high reactivity, alkali metals are found in nature only in compound form.