Question

Hydrogen shows (1) \(+1\) oxidation state only (2) \(-1\) oxidation state only (3) zero oxidation state only (4) \(+1,-1\) and zero oxidation states

Short answer

Option 4: +1, -1, and zero oxidation states.

Step-by-step solution

Understand Hydrogen's Oxidation States

Hydrogen can exhibit multiple oxidation states in different compounds. It varies depending on the nature of the substance it is part of.

Identify Common Oxidation States

Hydrogen commonly exhibits three oxidation states: - \(+1\): When hydrogen is bonded with non-metals (e.g., HCl). - \(-1\): When hydrogen is bonded with metals, forming hydrides (e.g., NaH). - \0\: In molecular hydrogen (H_2).

Match the Identified States to Options

From the identified oxidation states (\+1\, \-1\, and 0), the answer should include all three possible states. Therefore, we need to select the option that indicates \(+1, -1,\) and \(0\).

Choose Correct Option

Review the provided options: 1. \(+1\) oxidation state only. 2. \(-1\) oxidation state only. 3. Zero oxidation state only. 4. (Correct) \(+1, -1,\) and zero oxidation states.

Key concepts

Hydrogen Oxidation States

Hydrogen is unique because it can exhibit multiple oxidation states depending on the compounds it forms. The oxidation state of an element is a measure of the degree of oxidation of an atom in a chemical compound. Understanding the oxidation states of hydrogen is crucial as it affects how hydrogen behaves in chemical reactions.

Hydrogen can adopt three distinct oxidation states:

• +1: This occurs when hydrogen bonds with non-metals such as in hydrochloric acid (HCl). In this state, hydrogen has lost one electron.
• -1: This is observed when hydrogen bonds with metals forming compounds known as hydrides. For example, in sodium hydride (NaH), hydrogen gains one electron.
• 0: This occurs in molecular hydrogen (H_2), where two hydrogen atoms share electrons equally.

Recognizing these states helps predict how hydrogen will interact with other elements.
In the given exercise, you should select the option that includes all three states. Therefore, the correct answer is (+1, -1, and 0).

Chemical Bonding

Chemical bonding describes how atoms combine to form molecules. There are several types of chemical bonds, but the most relevant to hydrogen are ionic and covalent bonds.

• Covalent Bond: This is when atoms share electrons. In HCl, a covalent bond forms between hydrogen and chlorine. Hydrogen typically forms a +1 oxidation state in such compounds because it shares its only electron with chlorine.
• Ionic Bond: This type of bond occurs when one atom donates an electron to another atom. In compounds like NaH, an ionic bond forms between sodium and hydrogen. Hydrogen adopts a -1 oxidation state in these cases, as it gains an electron from sodium.

Understanding these interactions helps explain the variability in hydrogen's oxidation states. It all depends on the kind of bond it forms with other elements.
So, whether hydrogen goes +1 or -1 depends largely on whether it's forming a covalent or ionic bond.

Hydrides

Hydrides are compounds where hydrogen is bonded with a more electropositive element, usually a metal. In hydrides, hydrogen typically exhibits a -1 oxidation state.

There are several types of hydrides:

• Ionic Hydrides: These are formed when hydrogen bonds with alkali or alkaline earth metals such as sodium (NaH) or calcium (CaH_2). In these hydrides, hydrogen has a -1 oxidation state.
• Covalent Hydrides: These are formed when hydrogen bonds covalently with non-metals like in ammonia (NH_3) or methane (CH_4). These involve shared electrons, usually resulting in a +1 state for hydrogen.
• Metallic Hydrides: These are formed when hydrogen is absorbed into metals, often transition metals. Their exact oxidation state can be variable and not always well-defined.

Knowing about hydrides helps understand in what contexts hydrogen will exhibit a -1 oxidation state, as opposed to the +1 state seen with non-metals.
For the given exercise, recognizing the formation of hydrides is key to understanding the variability in hydrogen's oxidation states.