Question

On some periodic tables, hydrogen is listed both as a member of Group 1 and as a member of Group 7 . Write an equation showing the formation of \(\mathrm{H}^{+}\) ion and an equation showing the formation of \(\mathrm{H}^{-}\) ion.

Short answer

The formation of H+ ion can be represented by the equation: \[\mathrm{H} \rightarrow \mathrm{H}^{+} + e^{-}\] The formation of H- ion can be represented by the equation: \[\mathrm{H} + e^{-} \rightarrow \mathrm{H}^{-}\]

Step-by-step solution

Formation of H+ ion

Hydrogen loses an electron to form a positive ion (H+). The reaction is as follows: \[\mathrm{H} \rightarrow \mathrm{H}^{+} + e^{-}\] Here, Hydrogen (H) loses an electron (e-) to become a positively charged ion (H+).

Formation of H- ion

Hydrogen gains an electron to form a negative ion (H-). The reaction is as follows: \[\mathrm{H} + e^{-} \rightarrow \mathrm{H}^{-}\] In this reaction, Hydrogen (H) gains an electron (e-) to become a negatively charged ion (H-).

Key concepts

Group 1 elements

Known as the alkali metals, Group 1 elements are characterized by their highly reactive nature, particularly with water, and their tendency to lose one electron to form a cation. The elements in this group include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

These elements all have a single electron in their outermost shell which makes them eager to donate that electron in chemical reactions, forming positively charged ions. For instance, when sodium reacts, it can be represented as:
\[\begin{equation} \mathrm{Na} \rightarrow \mathrm{Na}^{+} + e^{-}\end{equation}\]In this process, sodium (Na) loses one electron (e-) and becomes a positively charged sodium ion (Na+).

Group 7 elements

Group 7 elements, also known as the halogens, are highly reactive nonmetals that include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Their high reactivity is due to their electronegativity and the desire to gain an electron to achieve a stable electronic configuration.

These elements have seven electrons in their outer shell and typically form anions by gaining an electron during reactions. A typical reaction involving a halogen, such as chlorine, can be represented as:
\[\begin{equation}\mathrm{Cl} + e^{-} \rightarrow \mathrm{Cl}^{-}\end{equation}\]Through this reaction, chlorine (Cl) gains an electron (e-) resulting in a negatively charged chloride ion (Cl-).

Cation and anion formation

Cations are positively charged ions formed when an atom loses one or more electrons. Anions, on the other hand, are negatively charged ions created by the gain of one or more electrons.

For instance, during the formation of a sodium cation (Na+), an electron is removed:\[\begin{equation}\mathrm{Na} \rightarrow \mathrm{Na}^{+} + e^{-}\end{equation}\]Consequently, a substance like chlorine forms an anion (Cl-) by acquiring an electron:\[\begin{equation}\mathrm{Cl} + e^{-} \rightarrow \mathrm{Cl}^{-}\end{equation}\]The process of forming cations and anions is fundamental in chemical bonding and occurs during various chemical reactions.

Chemical reactions

Chemical reactions involve the reorganization of atoms and the transfer of electrons, leading to the formation of new substances. These reactions are described by equations that show the reactants transforming into products.

During these reactions, atoms seek to achieve a full outer shell of electrons resulting in stable electronic configurations. When an atom donates or accepts electrons, this is referred to as a redox reaction. For example, the formation of hydrogen ions can be shown through the following reactions:\[\begin{equation}\mathrm{H} \rightarrow \mathrm{H}^{+} + e^{-}\end{equation}\]
and for a hydride ion:\[\begin{equation}\mathrm{H} + e^{-} \rightarrow \mathrm{H}^{-}\end{equation}\]
These reactions exhibit the dual potential of hydrogen to either lose or gain an electron. The simplified representations of these processes are key for students to visualize and comprehend the essence of redox chemistry.