Question

What is the charge on the common monatomic ions of the following elements? (a) selenium (b) fluorine (c) iron (d) nitrogen

Short answer

(a) -2; (b) -1; (c) +2 or +3; (d) -3.

Step-by-step solution

Determine the Charge for Selenium

Selenium is in Group 16 of the periodic table, which has an oxidation state of -2. Monatomic ions from Group 16 elements typically gain 2 electrons to form anions with a -2 charge.

Determine the Charge for Fluorine

Fluorine is in Group 17 of the periodic table. Elements in this group usually gain 1 electron to form anions with a -1 charge. Thus, fluorine forms a monatomic ion with a charge of -1.

Determine the Charge for Iron

Iron, a transition metal, can have more than one common oxidation state. It typically forms monatomic ions with charges of +2 (ferrous) and +3 (ferric).

Determine the Charge for Nitrogen

Nitrogen is in Group 15 of the periodic table. It typically gains 3 electrons to form anions with a -3 charge when forming a monatomic ion.

Key concepts

Oxidation State

The oxidation state, also known as oxidation number, is a value that represents the total number of electrons an atom either gains or loses in order to form a bond. In simple terms, it suggests how an element interacts with others to form compounds.

Elements in the same group of the periodic table often exhibit similar oxidation states because they have the same number of valence electrons. Valence electrons are the outer electrons that are involved in chemical bonding.

• An element's oxidation state can help predict the compound it will form.
• For instance, if an element has an oxidation state of -2, it will likely gain two electrons in chemical reactions.
• If an element exhibits multiple oxidation states, like iron, it can participate in different types of chemical reactions.

Understanding oxidation states is crucial for determining the charge of monatomic ions, as these numbers guide whether an atom becomes positively or negatively charged.

Periodic Table Groups

The periodic table is organized into columns called groups, each containing elements with similar chemical properties. These similarities occur because elements in the same group have the same number of valence electrons.

Here's how some of the groups work:

• Group 15: Elements like nitrogen have five valence electrons and usually form ions with a -3 charge by gaining three electrons.
• Group 16: Elements like selenium have six valence electrons and typically form ions with a -2 charge by gaining two electrons.
• Group 17: These elements, like fluorine, have seven valence electrons and generally form ions with a -1 charge by gaining one electron.

The number of valence electrons influences an element's chemical behavior, allowing you to predict how an element might form ions and bonds. Understanding groups helps in deciphering an element’s properties and its role in chemical reactions.

Anion Charge

Anions are negatively charged ions, which form when an atom gains electrons. The charge of an anion depends on how many electrons an atom gains, which is directly influenced by the number of valence electrons.

For example:

• Fluorine typically gains one electron, forming an anion with a -1 charge (F^-).
• Selenium usually gains two electrons, resulting in an anion with a -2 charge (Se^2-).
• Nitrogen generally gains three electrons to become an anion with a -3 charge (N^3-).

Anions are crucial in forming ionic compounds, where they combine with cations (positively charged ions) to create stable compounds. Focusing on the anion charge can aid in predicting the formula of compounds these elements may form. Knowing how different groups of elements tend to form anions allows you to quickly determine their charges.

Transition Metals

Transition metals occupy the central block of the periodic table and are characterized by their ability to form multiple oxidation states. This is largely due to their d-orbitals, which can involve more electrons in forming bonds.

Here’s what makes transition metals unique:

• Variable Oxidation States: Unlike groups 15-17, transition metals like iron can have more than one common oxidation state. Iron can be found in the +2 (ferrous) and +3 (ferric) states.
• Colored Compounds: Many compounds of transition metals are colored, a property resulting from d-d electron transitions.
• Catalytic Properties: Transition metals and their compounds make excellent catalysts in industrial reactions because of their variable oxidation states.

In learning about transition metals, it is vital to understand their versatile nature. This knowledge assists in recognizing how they can partake in diverse chemical reactions, further enriched by their ability to switch between different oxidation states.