- Beryllium has 2 valence electrons and forms a \(\text{Be}^{2+}\) ion to achieve stability.
- Fluorine has 7 valence electrons and gains 1 electron to form an \(\text{F}^{-}\) ion to achieve an octet.
- To balance the charges, one \(\text{Be}^{2+}\) ion combines with two \(\text{F}^{-}\) ions.
- The resulting chemical formula for the compound is \(\boxed{\text{BeF}_2}\).
Explanation
- Determine the charge of the Beryllium ion
Beryllium (Be) has an atomic number of 4. Its electron configuration is \(1s^2 2s^2\). Beryllium has two valence electrons in its outermost \(2s\) orbital. To achieve a stable, filled shell configuration like the noble gas helium, beryllium readily loses these two valence electrons, resulting in a beryllium ion with a \(+2\) charge, denoted as \(\text{Be}^{2+}\).
- Determine the charge of the Fluorine ion
Fluorine (F) has an atomic number of 9. Its electron configuration is \(1s^2 2s^2 2p^5\). Fluorine has seven valence electrons in its outermost shell. To achieve a stable, full octet configuration like the noble gas neon, fluorine needs to gain one electron. Consequently, when it gains an electron, it forms a fluoride ion with a \(-1\) charge, denoted as \(\text{F}^{-}\).
- Determine the ratio of ions for electrical neutrality
For an ionic compound to be electrically neutral, the total positive charge must equal the total negative charge. We have a cation \(\text{Be}^{2+}\) and an anion \(\text{F}^{-}\). To balance one \(\text{Be}^{2+}\) ion (which has a \(+2\) charge), we need two \(\text{F}^{-}\) ions (each with a \(-1\) charge) because \(2 \times (-1) = -2\), and \(+2 + (-2) = 0\). Thus, the ions combine in a \(1:2\) ratio.
- Conclusion and correct formula
Using the calculated ratio of one beryllium ion to two fluoride ions, the chemical formula is written by placing the symbol for each element followed by a subscript indicating the number of atoms in the simplest ratio. Therefore, the formula is \(\text{BeF}_2\). This matches the first option provided.
Examples
Chemical formulas are essential in understanding how different materials react in the real world. For instance, in manufacturing, chemists use these formulas to determine the precise amounts of raw materials needed to synthesize new substances like ceramics, glass, or even medicine. Knowing that Beryllium and Fluorine combine in a 1:2 ratio allows engineers to design experiments and industrial processes that ensure safety and efficiency, avoiding waste and dangerous byproducts. Understanding valency helps predict how components in a complex system will interact, which is fundamental to everything from battery design to environmental science.