Problem 52 - Chemistry Matter and Change

Question

Give the number of valence electrons in an atom of each element. \(\begin{array}{ll}{\text { a. cesium }} & {\text { d. zinc }} \\ {\text { b. rubidium }} & {\text { e. strontium }} \\ {\text { c. gallium }}\end{array}\)

Step-by-Step Solution

Answer

Cesium: 1; Rubidium: 1; Gallium: 3; Zinc: 2; Strontium: 2.

Step 1: Understanding Valence Electrons

Valence electrons are the electrons in the outermost shell of an atom. They are important for chemical bonding.

Step 1: Cesium

Cesium ( ext{Cs}) is an alkali metal located in group 1 of the periodic table. Every group 1 element has 1 valence electron.

Step 2: Rubidium

Rubidium ( ext{Rb}) is also an alkali metal in group 1. Therefore, rubidium has 1 valence electron.

Step 3: Gallium

Gallium ( ext{Ga}) is in group 13 of the periodic table. Group 13 elements have 3 valence electrons.

Step 4: Zinc

Zinc ( ext{Zn}) is in group 12. Transition metals in this group have 2 valence electrons.

Step 5: Strontium

Strontium ( ext{Sr}) is located in group 2 of the periodic table. Elements in this group have 2 valence electrons.

Key Concepts

Periodic Table

The periodic table is like a treasure map for chemists. It organizes all known chemical elements in a grid defined by increasing atomic number. The table is structured in rows and columns, known as periods and groups, respectively. Each element is represented by a unique symbol. Elements are arranged in order of increasing atomic numbers,
so elements with similar properties appear at regular intervals, the periodicity that gave the periodic table its name.

• Group: Vertical columns in the periodic table are called groups. They often contain elements that have similar chemical properties due to having the same number of valence electrons.
• Period: Horizontal rows are called periods. Elements in the same period have the same number of atomic orbitals.

For example, in the periodic table, both cesium (Cs) and rubidium (Rb) belong to Group 1, which is known for its highly reactive metals.

Chemical Bonding

Chemical bonding refers to the attraction between atoms that enables the formation of chemical substances containing two or more atoms. Bonds are formed when valence electrons, the electrons in the outermost shell of an atom,
are shared or transferred between atoms. This process helps atoms achieve more stable electron configurations, often resembling those of noble gases.

• Ionic Bonds: Formed when electrons are transferred from one atom to another, often between metals and nonmetals.
• Covalent Bonds: Formed when two atoms share one or more pairs of electrons, typically between nonmetals.
• Metallic Bonds: Found in metals, where valence electrons are shared across many atoms, allowing for conductivity and malleability.

Understanding chemical bonding is crucial when determining how elements like cesium and rubidium interact in chemical reactions.

Group Elements

Elements within the same group in the periodic table share the same number of valence electrons, resulting in similar chemical properties. This is why elements in the same group often behave in a similar way during chemical reactions.
For example:

• Group 1: Alkali metals such as lithium, sodium, and potassium each have one valence electron, making them highly reactive, especially with water.
• Group 2: Alkaline earth metals like magnesium and calcium have two valence electrons and are also quite reactive but not as aggressive as the Group 1 metals.
• Group 13: Includes elements like aluminium and gallium, which have three valence electrons.

The shared properties within a group help predict the behavior of elements in chemical reactions.

Alkali Metals

Alkali metals are found in Group 1 of the periodic table and include elements like lithium, sodium, potassium, rubidium, and cesium. These metals are known for having just one valence electron, which makes them extremely reactive. They are never found in their pure form in nature,
but always in compounds.
Key traits of alkali metals include:

• Soft texture and high reactivity
• Ability to conduct electricity
• Low density, with some even floating on water
• Reaction with water to produce hydrogen gas and a strong alkaline solution

Their reactivity increases down the group, with cesium being more reactive than lithium. Understanding alkali metals is important because their high reactivity plays a crucial role in various chemical reactions and applications.