Problem 50 - Chemistry: The Central Science

Question

Which of the following statements does not follow from the fact that the alkali metals have relatively weak metal-metal bonding? (a) The alkali metals are less dense than other metals. (b) The alkali metals are soft enough to be cut with a knife. (c) The alkali metals are more reactive than other metals. (d) The alkali metals have higher melting points than other metals. (e) The alkali metals have low ionization energies.

Step-by-Step Solution

Answer

The statement that does not follow from the fact that alkali metals have relatively weak metal-metal bonding is (d) The alkali metals have higher melting points than other metals.

Step 1: Understand the Properties of Alkali Metals

Alkali metals are the elements belonging to Group 1 of the periodic table. They have a single electron in their outermost shell, which they can easily lose to form a positive ion. Due to weak metal-metal bonding, alkali metals have specific properties, such as low density, softness, high reactivity, low melting points, and low ionization energies. We will now evaluate each statement to see if it is a result of weak metal-metal bonding.

Step 2: Statement (a): Density

Alkali metals have relatively weak metal-metal bonding, which results in a less compact crystal lattice structure. This leads to the alkali metals being less dense than other metals. Therefore, statement (a) is true and follows from the given fact.

Step 3: Statement (b): Softness

The weak bonding in alkali metals allows their atoms to slide past one another more easily, making them softer than other metals. This is why alkali metals such as sodium and potassium can be cut with a knife. Statement (b) is true and follows from the given fact.

Step 4: Statement (c): Reactivity

Alkali metals are highly reactive due to their ability to lose their single outer electron easily. This property is directly related to weak metal-metal bonding. As a result, statement (c) is true and follows from the given fact.

Step 5: Statement (d): Melting Points

Due to weak metal-metal bonding, alkali metals have low melting points compared to other metals because less energy is required to overcome the weak bonding. However, the statement (d) says that alkali metals have higher melting points than other metals, which is the opposite of the expected property. Therefore, statement (d) is false and does not follow from the given fact.

Step 6: Statement (e): Ionization Energies

Alkali metals have low ionization energies due to their weak metal-metal bonding, which allows them to lose an electron easily, forming a positive ion. Hence, statement (e) is true and follows from the given fact. So, the statement that does not follow from the fact that alkali metals have relatively weak metal-metal bonding is (d) The alkali metals have higher melting points than other metals.