Question

Explain why the reaction of calcium and fluorine does not form CaF \(_{3}\).

Short answer

Calcium reacts with fluorine to form CaF extsubscript{2} due to charge balance requirements.

Step-by-step solution

Understanding Calcium and Fluorine Interaction

Calcium is an alkaline earth metal with the chemical symbol Ca. It is in group 2 of the periodic table and has an oxidation state of +2. Fluorine, with the chemical symbol F, is a halogen found in group 17 and typically has an oxidation state of -1.

Determining the Stable Ionic Compound

In stable ionic compounds, total positive charges must equal total negative charges. Since calcium has an oxidation state of +2 and fluorine has an oxidation state of -1, two fluorine atoms are needed to neutralize the +2 charge from one calcium atom, leading to the formula CaF extsubscript{2}, not CaF extsubscript{3}.

Balancing the Charges

CaF extsubscript{3} would imply that three fluorine atoms are used, contributing a total charge of -3. This would leave the +2 charge from calcium unbalanced, resulting in an unstable ionic compound. Thus, Ca and F naturally form CaF extsubscript{2} by balancing the charges.

Key concepts

Chemical Reactions

Chemical reactions involve the transformation of substances through breaking and forming bonds. In the case of calcium and fluorine, when these elements come into contact, they undergo a chemical reaction to achieve stability. Atoms like calcium, an alkaline earth metal, and fluorine, a halogen, strive to reach electron configurations that resemble noble gases.
An important principle is that reactions tend to favor products that are more stable than the reactants. For calcium and fluorine, stability is reached when they form ionic bonds, where calcium donates electrons and fluorine accepts them. This forms a stable compound, specifically calcium fluoride with the formula \( \text{CaF}_2 \).
In chemical reactions, the driving force often involves reaching a low-energy state by achieving full outer electron shells. This is why calcium sulfide (CaF₂) is formed rather than an unstable compound like CaF₃. The reaction respects the balance of charges, leading to a stable product.

Oxidation States

Oxidation states are crucial for understanding how elements interact in chemical reactions. They indicate the potential charge of an atom if electrons were transferred completely.
Calcium typically exhibits an oxidation state of +2. This means calcium loses two electrons during reactions. Fluorine, on the other hand, exhibits an oxidation state of -1, indicating it gains one electron.
Understanding these states helps in predicting the formula of compounds formed. Given that calcium has a +2 charge and each fluorine has a -1 charge, to neutralize the charge, two fluorine atoms are required, resulting in \( \text{CaF}_2 \). This ensures that the total charges balance, creating an electrically neutral compound.
The oxidation states act as a guide to predict not only the composition of compounds but also their stability. A mismatch in these states, such as in a hypothetical \( \text{CaF}_3 \), would lead to an unequal charge and instability.

Periodic Table

The periodic table provides a framework for predicting the behavior and reactivity of elements. It arranges elements by increasing atomic numbers and groups them by similar properties.
Calcium, found in group 2, is known for losing electrons easily, contributing to its reactivity and tendency to form +2 charges. This is a characteristic of alkaline earth metals. Fluorine, in group 17, is highly electronegative and seeks to gain electrons, forming a -1 charge.
The periodic table not only shows elemental properties like atomic numbers and symbols, but it also hints at the type of bonds elements will form.
By examining the table, one can predict that calcium will likely pair with halogens like fluorine to form ionic compounds. This understanding ascribes to calcium its role as a donor of electrons, while fluorine acts as an acceptor, culminating in a balanced and stable compound such as \( \text{CaF}_2 \). The periodic table thus acts as a roadmap for determining possible chemical interactions and compound formations.