Which of the following metals is classified as an alkali metal, and why does it exhibit the highest reactivity with water compared to others in this group?

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Potassium - It has a higher atomic mass and a full outer electron shell.

Lithium - It has one electron in its outer shell and is less reactive than the others.

Sodium - Its atomic structure allows it to easily lose its outer electron, making it reactive.

Rubidium - It has a lower ionization energy than sodium.

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The metal that is classified as an alkali metal and shows the highest reactivity with water is cesium. Cesium belongs to the alkali metals because it has a single valence electron that it can lose very easily. Its large atomic radius keeps that electron far from the nucleus, so the ionization energy is very low and the electron is weakly held. When cesium contacts water it is almost instantly oxidized, forming cesium hydroxide and releasing hydrogen gas, a reaction that is much more violent than for lithium, sodium, potassium, rubidium or cesium. For example, a small piece of cesium metal placed in water produces a large, hot bubble of hydrogen and a bright orange flame, illustrating its extreme reactivity.

Detailed Explanation

Sodium has one electron in its outer shell, and it is very easy to lose this electron. Other options are incorrect because A common idea is that heavier atoms like potassium are always more reactive because they weigh more; Lithium is often thought to be the most reactive because it also has a single outer electron.

Key Concepts

Alkali Metals

Chemical Reactivity

Ionization Energy

Topic

Alkali Metals

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hard level question

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Question 1

Which chemical property of potassium (K) distinguishes it from other alkali metals?

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Question 2

Alkali metals are known for their high reactivity, particularly with ______, resulting in the formation of hydroxides and the release of hydrogen gas.

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Question 3

When alkali metals react with water, they produce hydrogen gas and a hydroxide. What is the primary reason for the high reactivity of alkali metals with water?

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Question 4

Which property of alkali metals primarily explains their vigorous reaction with water?

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Question 5