Question

a. Which elements are designated as the alkaline- earth metals? b. How do their characteristic properties compare with those of the alkali metals?

Short answer

a. Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), Radium (Ra). b. Harder, denser, higher melting points, and less reactive than alkali metals.

Step-by-step solution

Identify the Alkaline-Earth Metals

The alkaline-earth metals are located in Group 2 of the periodic table. This group includes Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra).

Compare Properties with Alkali Metals

Alkaline-earth metals (Group 2) are harder and denser than alkali metals (Group 1). They have higher melting points and are less reactive compared to the alkali metals, which are extremely reactive and soft with low melting points.

Key concepts

Alkali Metals

Alkali metals are fascinating elements located in Group 1 of the periodic table. They include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). One key feature of alkali metals is their high reactivity, especially with water. For example, dropping a piece of sodium in water can result in a vigorous reaction that produces hydrogen gas and an alkaline solution.
Another characteristic is their soft texture. In fact, you can cut some alkali metals, like potassium, with a knife. They also have relatively low melting points, unlike most metals.
Here are a few more points about alkali metals:

• They have a single electron in their outermost shell, making them very reactive.
• They are good conductors of electricity.
• Their density is low, which allows them to float on water.

Given these attributes, alkali metals are quite different from many other elements on the periodic table.

Periodic Table

The periodic table is an organized chart of all known chemical elements. Each element is placed in the table based on its atomic number, which is the number of protons in its nucleus. Elements are also grouped into columns known as 'groups' or 'families' that share similar chemical properties.
For example, Group 1 contains the alkali metals, while Group 2 is home to the alkaline-earth metals. The periodic table also has rows called 'periods', which indicate the number of electron shells an atom has.
Here are a few other important features of the periodic table:

• Metals are found on the left side and in the middle of the table.
• Non-metals are located on the right side.
• Metalloids, which have properties of both metals and non-metals, are situated between metals and non-metals.

Understanding the periodic table is essential for studying chemistry because it helps predict the types of chemical reactions an element can undergo.

Chemical Properties Comparison

When comparing chemical properties, especially between alkaline-earth metals and alkali metals, several key differences emerge. Alkaline-earth metals are in Group 2 of the periodic table and include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). These elements are harder and denser compared to alkali metals of Group 1.
Here are some points of comparison:

• Alkali metals have only one electron in their outer shell, making them highly reactive. Alkaline-earth metals have two electrons, which makes them less reactive.
• Melting points: Alkali metals have lower melting points, while alkaline-earth metals have higher melting points.
• Density: Alkali metals are less dense, so they can float on water. Alkaline-earth metals are denser.
• Reactivity with water: Alkali metals react much more vigorously with water than alkaline-earth metals.

These characteristics make alkaline-earth metals quite different from alkali metals, even though they are adjacent to each other on the periodic table.