Understanding Water Composition: Which Element Combines with Hydrogen?

The question asks us to identify the element that combines with hydrogen atoms to form water. Water is one of the most common and essential substances on Earth. Its chemical composition is well-defined.

The chemical formula for water is known to be H\(_2\)O. This formula tells us exactly which elements are present in a water molecule and in what proportion.

• The 'H' in the formula stands for the element Hydrogen.
• The 'O' in the formula stands for the element Oxygen.
• The subscript '2' next to 'H' indicates that there are two atoms of hydrogen in each water molecule.
• When there is no subscript next to an element symbol (like 'O'), it means there is one atom of that element in the molecule.

Therefore, the chemical formula H\(_2\)O shows that one molecule of water is made up of two hydrogen atoms and one oxygen atom. This directly tells us that hydrogen atoms combine with oxygen atoms to form water.

Chemical Reaction to Form Water

Water is formed when hydrogen gas (H\(_2\)) reacts with oxygen gas (O\(_2\)). The balanced chemical equation for this reaction is:

\(2\text{H}_2\text{(g)} + \text{O}_2\text{(g)} \rightarrow 2\text{H}_2\text{O(l)}\)

This equation shows that hydrogen and oxygen combine chemically under suitable conditions to produce water. The reaction involves the atoms of hydrogen and oxygen rearranging to form new chemical bonds in water molecules.

Analyzing the Options

Let's look at the given options and see which one fits the chemical composition of water:

1. Iodine: Iodine is a halogen element (symbol I). It does not combine with hydrogen to form water. It can form hydrogen iodide (HI), which is a different compound.
2. Oxygen: Oxygen is a non-metal element (symbol O). As we saw from the formula H\(_2\)O, oxygen atoms combine with hydrogen atoms to form water. This matches the known composition of water.
3. Carbon: Carbon is an element (symbol C) that forms a vast number of compounds, particularly organic compounds. Carbon combines with hydrogen to form hydrocarbons (like methane, CH\(_4\)), not water.
4. Nitrogen: Nitrogen is an element (symbol N) that makes up a large part of the Earth's atmosphere. Nitrogen combines with hydrogen to form ammonia (NH\(_3\)), not water.

Based on the chemical formula of water (H\(_2\)O) and the elements involved in its formation, Oxygen is the element that combines with hydrogen to give water.

Conclusion

The element that combines with hydrogen to form water is Oxygen, as represented by the chemical formula H\(_2\)O.

Revision Table: Water Formation Key Concepts

Additional Information: Properties of Hydrogen and Oxygen

Understanding the properties of Hydrogen and Oxygen helps explain why they combine to form water.

• Hydrogen (H): It is the lightest element. It exists as a diatomic gas (H\(_2\)) under normal conditions. It is highly flammable and reacts readily with oxygen.
• Oxygen (O): It is a highly reactive non-metal. It exists as a diatomic gas (O\(_2\)) under normal conditions. Oxygen is essential for combustion and respiration. When hydrogen and oxygen react, they form strong bonds, releasing a significant amount of energy, which is why the reaction can be explosive.

The combination of these two elements results in water, a stable compound with properties vastly different from its constituent elements, such as being a liquid at room temperature and being essential for life.