Problem 82 - Chemistry Matter and Change

Question

\(\begin{array}{l}{\text { Milk The element with the electron configuration }} \\\ {[\text { Ar }] 4 \mathrm{s}^{2} \text { is an important mineral in milk. Identify this }} \\ {\text { element's group, period, and block in the periodic table. }}\end{array}\)

Step-by-Step Solution

Answer

Calcium is in Group 2, Period 4, and the s-block.

Step 1: Identify Element from Electron Configuration

The given electron configuration is \([ ext{Ar}] 4s^2\). This indicates the element has filled up to argon's electron configuration, which ends with \(3p^6\), and additionally has two electrons in the \(4s\) subshell. This corresponds to the element calcium (Ca) in the periodic table.

Step 2: Identify the Period

The period of an element is determined by the principal quantum number of the outermost shell containing electrons. The outermost shell in calcium is \(n = 4\), so calcium is in the 4th period of the periodic table.

Step 3: Identify the Group

In the periodic table, elements in the \(s\)-block that have two electrons in their outermost \(s\) subshell belong to Group 2. Therefore, calcium belongs to Group 2.

Step 4: Identify the Block

The block of an element is determined by the type of atomic orbital that is being filled last. As the last filled electrons are in the \(4s\) orbital, calcium is in the \(s\)-block.

Key Concepts

Electron Configuration

Electron configuration is a way of representing the arrangement of electrons around an atom's nucleus. It indicates the occupancy of electrons in different atomic orbitals. For example, the electron configuration

• Starts with the notation for a noble gas (like [Ar]), showing its underlying structure is like that of argon.
• Follows with orbitals, like "4s²", showing additional electrons beyond the core.

This notation helps us determine properties and chemical behaviors of the elements by revealing how electrons fill various energy levels.

Calcium

Calcium is a chemical element with the symbol Ca. In the periodic table, it is represented with the atomic number 20. Characterized by its silvery-white metallic appearance, calcium is vital for living organisms. Its electron configuration is \([ ext{Ar}] 4s^2\), indicating that after filling up to argon, two electrons occupy the 4s subshell.

Calcium plays a key role in biological processes such as bone formation and the functioning of muscles and nerves. It's an essential part of many dairy products like milk and cheese.

Groups and Periods

The periodic table is organized into groups and periods.

• Groups: The vertical columns, referred to as groups, contain elements with similar properties. This reason is because they have the same number of valence electrons.
• Periods: The horizontal rows known as periods display elements with increasing atomic numbers. The period number indicates the highest energy level where electrons are present in an atom. For calcium, the period is 4 because its outermost electrons are in the 4th shell.

This organization helps predict element properties and reactivity by observing their position on the table.

s-Block Elements

s-Block elements are found on the left side of the periodic table. Their valence electrons fill in the 's' orbital, a spherical orbit close to the nucleus. Elements in this block have important traits:

• Contain Groups 1 and 2.
• Typically very reactive metals.
• Good conductors of electricity.

Calcium is part of the s-block because its outer electrons are filled in the 4s orbital. Understanding s-block dynamics is crucial as these elements dramatically influence both chemical reactions and biological functions.