Question

Among the following group of clements the one whose clements can have positive as well as negative oxidation states. (1) \(\mathrm{H}, \mathrm{F}, \mathrm{O}\) (2) \(\mathrm{Na}, \mathrm{M}_{\mathrm{g}}, \mathrm{Al}\) (3) \(\mathrm{He}, \mathrm{Li}, \mathrm{Be}\) (4) \(\mathrm{H}, \mathrm{Cl}, \mathrm{Br}\)

Short answer

Group (4) \( \text{H, Cl, Br} \) contains elements with both positive and negative oxidation states.

Step-by-step solution

Understand Oxidation States

Oxidation states, also known as oxidation numbers, represent the degree of oxidation (loss of electrons) of an atom in a chemical compound. Elements may have multiple oxidation states, including positive and negative ones.

Analyze Each Group

Examine each group of elements to determine if they have both positive and negative oxidation states:(1) \(\text{H, F, O}\): Hydrogen (H) can have \(+1\) and \(-1\), Fluorine (F) only \(-1\), Oxygen (O) can have \(-2, -1, 0, +1, +2\).(2) \(\text{Na, Mg, Al}\): Sodium (Na) \(+1\), Magnesium (Mg) \(+2\), and Aluminum (Al) \(+3\) typically only have positive oxidation states.(3) \(\text{He, Li, Be}\): Helium (He) has no oxidation states as it is a noble gas, Lithium (Li) \(+1\), Beryllium (Be) \(+2\), all with positive only.(4) \(\text{H, Cl, Br}\): Hydrogen (H) can have \(+1\) and \(-1\), Chlorine (Cl) \(-1, +1, +3, +5, +7\), Bromine (Br) \(-1, +1, +3, +5, +7\).

Identify the Group with Both Oxidation States

Considering all groups analyzed, Group (4) \( \text{H, Cl, Br} \) has elements that can have both positive and negative oxidation states. Specifically, Hydrogen has \( +1, -1 \), Chlorine and Bromine have \( -1, +1, +3, +5, +7 \).

Key concepts

positive oxidation state

Oxidation states are a way to keep track of electron movement in chemical reactions. When an element loses electrons, the oxidation state becomes more positive. This happens because losing electrons, negatively charged particles, results in an overall positive charge. Elements like Sodium (Na), Magnesium (Mg), and Aluminum (Al) frequently have positive oxidation states. For example, Sodium typically has an oxidation state of +1, which means it loses one electron in reactions. Magnesium generally has an oxidation state of +2, losing two electrons. Understanding this helps in predicting how elements will behave in chemical reactions. Elements that can exhibit positive oxidation states are often metals, which readily lose electrons to form positive ions.

negative oxidation state

In a negative oxidation state, an element gains electrons. This makes the overall charge more negative. For instance, in the group analyzed, Fluorine (F) only has a -1 oxidation state because it readily gains one electron. Oxygen (O) often has a -2 oxidation state, gaining two electrons. Hydrogen (H), while commonly having a +1 oxidation state, can also have a -1 state when bonded with metals. Elements that tend to gain electrons often have higher electronegativities. Nonmetals like Chlorine (Cl) and Bromine (Br) can have multiple negative oxidation states, useful in redox reactions and compounds.

chemical compound

A chemical compound consists of two or more elements chemically bonded together. These bonds can be ionic (transfer of electrons) or covalent (sharing of electrons). Understanding the oxidation states of elements within a compound can predict the compound's properties and reactivity. For example, in water (H₂O), Hydrogen has a +1 oxidation state, and Oxygen has a -2 oxidation state. This difference in oxidation states helps explain water's polar nature, leading to its unique properties like high boiling point and excellent solvent abilities. Recognizing the oxidation states within a compound allows chemists to understand better and manipulate chemical reactions.