Question

Which of the following elements does not react with hydrogen? (a) neon (c) potassium (b) nitrogen (d) fluorine

Short answer

Neon does not react with hydrogen.

Step-by-step solution

Identify the Noble Gas

Noble gases like neon are known for their lack of reactivity due to having full valence electron shells. They rarely form compounds with other elements, including hydrogen.

Analyze Potassium

Potassium is an alkali metal, which reacts readily with hydrogen to form potassium hydride, a stable ionic compound.

Consider the Nitrogen

Nitrogen can react with hydrogen under specific conditions to form ammonia (NH₃), through the Haber process, which is widely used industrially.

Look at Fluorine

Fluorine is highly reactive and also reacts with hydrogen to form hydrogen fluoride (HF), a compound known for its strength and corrosive nature.

Key concepts

Noble Gases

Noble gases are a group of elements characterized by their large stability and low reactivity. They include helium, neon, argon, krypton, xenon, and radon. These elements are positioned in Group 18 of the periodic table. Their notable stability arises from having complete valence electron shells. This full outer electron shell minimizes energy variations, making these gases exceptionally inert. They do not typically engage in chemical reactions, as it would require them to gain, lose, or share electrons, which they have little tendency to do. Because of these unique properties, noble gases like neon do not react with other elements under standard conditions. This makes them reliable and safe to use in applications where non-reactivity is essential, such as in lighting and inert atmospheres for chemical processes.

Alkali Metals

Alkali metals represent the first group on the periodic table and include elements such as lithium, sodium, and potassium. These metals are incredibly reactive, especially with water and halogens. Their high reactivity can be attributed to their single valence electron, which they readily lose, forming positive ions. When it comes to hydrogen, alkali metals form hydrides, where hydrogen gains an electron to become a hydride ion. For example, potassium, an alkali metal, reacts with hydrogen to produce potassium hydride (KH). Potassium hydride is a powerful reducing agent and exists as a white crystalline solid. This reactivity is a hallmark of alkali metals, underscoring why they must be handled carefully, often under oil, to prevent unwanted reactions with air or moisture.

Ammonia Synthesis

Ammonia synthesis is an essential chemical process used to produce ammonia ( NH_3 ), mainly through the Haber process. This process involves the direct reaction of nitrogen and hydrogen gases. The Haber process requires specific conditions: high pressure (approximately 200 atmospheres) and high temperatures (around 450°C) in the presence of an iron catalyst. In this setting, nitrogen and hydrogen can combine to form ammonia efficiently. Ammonia is a crucial component in fertilizers and is vital for the production of various chemicals. Its synthesis demonstrates how even nitrogen, a relatively inert diatomic molecule, can form compounds under the right conditions, showcasing the versatility of chemical reactivity when principles such as catalysts and specific environmental conditions are applied.

Hydrogen Compounds

Hydrogen is a versatile element that forms compounds with a wide range of other elements, showcasing diverse chemical characteristics. One notable hydrogen compound is hydrogen fluoride ( HF ), which results from the reaction between hydrogen and fluorine. Fluorine is exceptionally reactive, and hydrogen fluoride exhibits unique properties such as being a corrosive liquid with the potential to form strong hydrogen bonds. Another important hydrogen compound is water ( H_2O ), the most abundant compound on Earth's surface and essential for all known forms of life. The ability of hydrogen to combine with both metals and nonmetals allows it to participate in forming compounds ranging from hydrates and hydrides to acids and hydrocarbons. This diversity highlights the critical role hydrogen plays in various chemical processes and the vast array of applications in everyday life.