Question

Predict which of the following metals reacts with water at room temperature: (a) Ba (b) Mn (c) Sn (d) K

Short answer

Potassium (K) reacts with water at room temperature.

Step-by-step solution

Identifying the Reactivity of Metals

Consider the reactivity series of metals when reacting with water. Metals like potassium, sodium, and calcium are known to react with water at room temperature. Other metals like barium (Ba), manganese (Mn), and tin (Sn) might not react under the same conditions.

Analyzing Group 1 Metals

Potassium (K) is in Group 1 of the periodic table, known as the alkali metals. These metals are highly reactive and react vigorously with water. Potassium is expected to react with water at room temperature.

Analyzing Group 2 Metals

Barium (Ba) is in Group 2, the alkaline earth metals. Ba may react with water, but its reaction is slower and not typical at room temperature. It's more reactive in hot water or when steam is involved.

Checking Other Metals

Manganese (Mn) and Tin (Sn) are generally unreactive with water at room temperature. Mn can react with water, but this usually requires higher temperatures. Sn is a metal that does not react with water under normal conditions.

Conclusion and Prediction

Based on the reactivity series and group characteristics, the metal that reacts with water at room temperature among the given options is potassium (K).

Key concepts

Reactivity Series

The reactivity series is a ranking of metals from most reactive to least reactive. This series is crucial for predicting how different metals will interact with water and other substances. It includes:

• Highly reactive metals such as potassium (K), sodium (Na), and calcium (Ca).
• Moderatively reactive metals like zinc (Zn) and iron (Fe).
• Less reactive metals, including copper (Cu) and silver (Ag).

This ordering helps us understand why some metals react readily with water, while others do not. For instance, potassium, being high on the series, reacts quickly with water, often explosively. However, metals further down like copper show no reaction. Understanding this series provides insights into chemical phenomena and guides practical applications such as metal extraction and recycling.

Alkali Metals

Alkali metals belong to Group 1 of the periodic table and include elements such as lithium (Li), sodium (Na), and potassium (K). These metals are characterized by their:

• Silvery appearance and softness.
• High reactivity, particularly with water and air.
• Formation of strong alkaline solutions when combined with water.

Reaction with water is a hallmark of alkali metals. When potassium, for example, contacts water, it produces potassium hydroxide (KOH) and hydrogen gas, often igniting due to the heat generated. This extreme reactivity is due to these metals having a single electron in their outer shell, making them eager to react and settle into a more stable electronic arrangement. Proper safety precautions are essential when handling these metals due to their explosive nature.

Alkaline Earth Metals

Alkaline earth metals are found in Group 2 of the periodic table. This group includes beryllium (Be), magnesium (Mg), calcium (Ca), and barium (Ba). Compared to alkali metals, these metals exhibit:

• Lower reactivity with water.
• Higher melting points.
• Presence of two electrons in their outer shell.

Though less reactive, they can still react with water under certain conditions. Barium's interaction with water forms barium hydroxide, but this reaction is less vigorous than with alkali metals and is typically more noticeable in heated conditions or with steam. Their moderate reactivity makes them useful in various industrial processes, including alloy formation and electronics.

Periodic Table Groups

The periodic table is structured in rows and columns, where columns are termed "groups." Each group shares common traits and reactivity trends. Group 1 includes alkali metals, while Group 2 consists of alkaline earth metals. This arrangement helps predict:

• Chemical behavior.
• Common ionization states.
• Similarities among elements within the same group.

Understanding periodic table grouping is essential for predicting how metals interact with other substances. For example, Group 1 metals, due to their lone electron, are highly reactive, especially with water, making their safety handling critical. Meanwhile, Group 2 metals' behavior is influenced by their two outer electrons, offering more moderate reactions. This logical and structured layout facilitates learning and predicting chemical behaviors effectively in chemistry.