Question

Which of the following statements is correct? (1) Alkali metals are less electropositive than alkaline earth metals. (2) The alkaline earth metals are denser and harder than alkali metals. (3) The alkali metals are denser and harder than alkaline earth metals. (4) The second IP of alkali metals is less than that of alkaline earth metals.

Short answer

(2) The alkaline earth metals are denser and harder than alkali metals.

Step-by-step solution

Identify the elements involved

Alkali metals are elements in Group 1 (e.g., Lithium, Sodium, Potassium). Alkaline earth metals are elements in Group 2 (e.g., Beryllium, Magnesium, Calcium).

Evaluate Statement (1)

Alkali metals are known for being highly electropositive, even more than alkaline earth metals. Therefore, this statement is incorrect.

Evaluate Statement (2)

Alkaline earth metals are typically denser and harder than alkali metals. This statement is correct.

Evaluate Statement (3)

Contrary to this statement, alkali metals are less dense and softer compared to alkaline earth metals. Therefore, this statement is incorrect.

Evaluate Statement (4)

The second ionization potential (IP) of alkali metals is higher than that of alkaline earth metals because removing the second electron from an alkali metal would require breaking into the stable noble gas configuration. Therefore, this statement is incorrect.

Key concepts

Electropositive Elements

Electropositive elements are those that tend to lose electrons easily to form positive ions. This is typically a property of metals.

Both alkali metals (Group 1) and alkaline earth metals (Group 2) are highly electropositive.

However, alkali metals are more electropositive than alkaline earth metals.
This is due to their atomic structure where alkali metals have only one electron in their outermost shell, making it easier to lose.

As a result, alkali metals react very quickly with non-metals and are often highly reactive
This property plays a significant role in their chemical behavior and helps distinguish them from alkaline earth metals.

Density and Hardness in Metals

When comparing the density and hardness of alkali and alkaline earth metals, there are some clear differences.

Alkaline earth metals tend to be denser and harder than alkali metals.
This happens because alkaline earth metals have a more compact atomic structure and stronger metallic bonds.

Here are some key points:

• Alkali Metals (e.g., Lithium, Sodium): Soft and less dense. Can be cut with a knife.
• Alkaline Earth Metals (e.g., Beryllium, Magnesium): Harder and denser. More difficult to cut or scratch.

The difference in density and hardness plays a significant role in their applications,
with alkaline earth metals typically being used in structures and alkali metals often being used in chemical reactions.

Ionization Potential

Ionization potential (IP) is the energy required to remove an electron from an atom in its gaseous state.
The first ionization potential refers to removing the first electron, and the second ionization potential refers to removing the second electron.

For alkali metals:

• The first IP is relatively low because they easily lose their single outer electron.
• The second IP is much higher because removing an electron after the first means breaking into a stable noble gas configuration.

For alkaline earth metals:

• The first IP is higher compared to alkali metals due to having two outer electrons.
• The second IP is lower than that of alkali metals because the removal of the second electron also leads to a stable configuration.

This difference in ionization potentials is crucial in understanding the reactivity and bonding nature of these metals in chemical reactions.