Question

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

Short answer

The element in milk with the electron configuration \([\mathrm{Ar}] 4\mathrm{s}^{2}\) is calcium (Ca) with 20 electrons. It is located in Group 2 (alkaline earth metals), Period 4, and Block s of the periodic table.

Step-by-step solution

Identify the Electron Configuration

The given electron configuration is [Ar] 4s^2. The notation [Ar] represents the noble gas argon in the periodic table, which has an atomic number of 18. This means the element that we are working with has 18 electrons from argon plus the 2 additional electrons in the 4s subshell, giving it a total of 20 electrons.

Locate the Element in the Periodic Table

Since our goal is to locate the element with 20 electrons, we can find it in the periodic table by locating an element with an atomic number of 20. Atomic numbers correspond to the number of electrons in the element. The element with an atomic number of 20 is calcium (Ca).

Determine the Element's Group, Period, and Block

Now that we know we are working with calcium, we can locate it in the periodic table and identify its group, period, and block. Calcium is located in: - Group 2: alkali earth metals - Period 4 - Block s So, the element in milk with the electron configuration [Ar] 4s^2 is calcium, and its group, period, and block are 2, 4, and s, respectively.

Key concepts

The Periodic Table

The periodic table is a comprehensive chart that scientists use to organize and categorize all the known elements. Each element on the periodic table is represented by a unique symbol, such as 'Ca' for calcium, and has a specific placement based on its atomic number, which indicates the number of protons (and, ordinarily, electrons) it has.

Elements are arranged in order of increasing atomic number from left to right and are grouped into rows called periods and columns known as groups or families. The table is structured in such a way that elements with similar chemical properties fall into the same group, offering a visual representation of these properties in the layout of the table. Understanding the periodic table is crucial when dealing with electron configurations, as it provides the key to determining the location and characteristics of an element.

Moreover, the table is divided into blocks, named according to the subshell that is being filled with electrons: s-block, p-block, d-block, and f-block. Knowing which block an element resides in helps in predicting its electron configuration and chemical reactivity.

Alkali Earth Metals

Alkali earth metals, found in Group 2 of the periodic table, are a family of elements that include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). They are called 'earth metals' because many of the compounds they form are found in the Earth's crust, and 'alkali' because they produce alkaline, or basic, solutions when reacting with water.

These metals are characterized by having two electrons in their outermost s subshell, indicated by the electron configuration ending in 's^2.' Alkali earth metals are known for their reactivity, although they are less reactive than the alkali metals in Group 1. They tend to lose their two outer electrons to form a +2 charge when participating in chemical reactions. Alkali earth metals have important applications; for instance, magnesium is used in the construction of lightweight materials, and calcium is a vital nutrient found in dairy products like milk.

Atomic Number

The atomic number of an element is a fundamental property that is unique to each element. It is defined as the number of protons found in the nucleus of an atom and determines the identity of the element. For neutral atoms, this also corresponds to the number of electrons because the charges must balance. The atomic number is used to order the elements on the periodic table and is generally displayed above the elemental symbol.

Finding an element in the periodic table is straightforward when you know its atomic number; locate the corresponding number, and you'll find the element. For example, as outlined in the exercise solution, calcium has an atomic number of 20, so it can easily be identified on the periodic table. The atomic number not only helps with identification but it also influences the chemical properties of the element, including its electron configuration. Understanding atomic numbers is fundamental in comprehending the structure of atoms and how they interact in chemical reactions.