Question

A member of the alkali metal family whose most stable ion contains 36 electrons forms a compound with chlorine. What is the correct formula for this compound?

Short answer

The alkali metal with its most stable ion having 36 electrons is Rubidium (Rb), which forms a +1 ion (Rb+). Chlorine forms a -1 ion called chloride (Cl-). These ions combine in a 1:1 ratio to form a neutral compound. Therefore, the correct formula for this compound is \(RbCl\).

Step-by-step solution

Determine the alkali metal with its most stable ion having 36 electrons

We first need to find out the alkali metal that forms a +1 ion with 36 electrons. Alkali metals have one electron in their outermost shell (Group 1 elements). When they lose that electron, they form a +1 ion. Thus, the neutral atom of the alkali metal will have 37 electrons (36 electrons in the ion +1 electron lost). The atomic number (number of protons) is equal to the number of electrons in a neutral atom. So, we are looking for the alkali metal with the atomic number 37. Based on the periodic table, the alkali metal with atomic number 37 is Rubidium (Rb).

Determine the ion of the chlorine

Chlorine (Cl) has an atomic number of 17, meaning it has 17 electrons as a neutral atom. It belongs to Group 17, so it tends to gain one electron to achieve a stable electron configuration. When it gains one electron, it forms a chloride ion (Cl-) with a -1 charge.

Combine the rubidium ion and chloride ion to find the correct formula

To form a compound, the ions must combine in a ratio that results in a neutral molecule (no charges). Since the Rubidium ion (Rb+) has a +1 charge and the chloride ion (Cl-) has a -1 charge, they can combine in a 1:1 ratio to form a neutral compound. This results in the formula RbCl. The correct formula for the compound formed between the alkali metal with 36 electrons in its most stable ion and chlorine is RbCl.

Key concepts

Alkali Metals

Alkali metals are found in Group 1 of the periodic table. They include elements like lithium, sodium, potassium, and rubidium. These metals have only one electron in their outermost shell, which makes them highly reactive.
This single valence electron can be easily lost, allowing them to form ions with a +1 charge. This property is important for forming bonds with other elements, especially non-metals like chlorine.
Alkali metals are known for their:

• Soft texture
• Low density
• High reactivity

For example, rubidium, an alkali metal with an atomic number of 37, readily loses its outer electron to achieve a stable ion with 36 electrons, forming the Rb+ ion. This behavior is common among all alkali metals, making them critical contributors to the formation of various ionic compounds.

Ionic Compounds

Ionic compounds are formed when metals and non-metals react. The metal typically loses electrons, becoming a positively charged ion, while the non-metal gains these electrons, becoming negatively charged. This exchange creates an ionic bond, which holds the two ions together due to opposite charges.
For instance, when rubidium (Rb) reacts with chlorine (Cl), rubidium loses one electron to become Rb+, and chlorine gains one electron to become Cl-. The result is a neutral ionic compound, RbCl, where the charges perfectly balance each other.
Characteristics of ionic compounds include:

• High melting and boiling points
• Solubility in water
• Ability to conduct electricity when dissolved

These properties are due to the strong electrostatic forces between the ions, which require a lot of energy to break. Understanding ionic compounds is crucial for grasping basic chemical bonding principles.

Periodic Table

The periodic table organizes all known chemical elements in a way that highlights their properties and relationships. Elements are arranged in order of increasing atomic number from left to right. The table's structure is such that elements with similar properties are aligned in columns, known as groups or families.
Alkali metals, for example, belong to Group 1, characterized by having a single electron in their outermost shell, leading to their high reactivity. Rubidium, an alkali metal, is located in this group and can be identified using its atomic number of 37.
The periodic table also helps us:

• Determine the atomic structure of elements
• Predict reactions based on element groups
• Understand trends like electronegativity and atomic size

By providing a comprehensive visual representation of elements, the periodic table is an essential tool for both studying and understanding chemistry.

Electrons

Electrons are subatomic particles with a negative charge. They are found in the electron cloud surrounding an atom's nucleus, which contains protons and neutrons. The arrangement of electrons in an atom determines its chemical properties and reactivity.
In alkali metals, like rubidium, there is only one electron in the outermost shell. When rubidium loses this lone electron, it achieves a more stable electron configuration, similar to that of the previous noble gas, krypton.
Key points about electrons include:

• They control the majority of an element's chemical behavior
• They participate in forming bonds between atoms
• They can be transferred or shared during chemical reactions

Understanding electrons and their interactions is fundamental to grasping how different elements form compounds and engage in various chemistries.