Question

Use Lewis symbols to represent the reaction that occurs between Ca and F atoms.

Short answer

The reaction between Calcium (Ca) and Fluorine (F) can be represented using Lewis symbols as follows: \[ \text{Ca} : \: +\: .\: .\: \text{F}\: . \: +\: .\: .\: \text{F}\: . \: \rightarrow \: [\text{Ca}]^{2+}\: +\: [\text{F}]\: -\: .\: .\: .\: . \: +\: [\text{F}]\: -\: .\: .\: .\: . \] The final chemical formula for the compound is \( CaF_2 \), which is Calcium fluoride.

Step-by-step solution

Identify the valence electrons

Each element has a specific number of valence electrons, which are the electrons in the outermost shell of an atom. For Calcium (Ca), which is in Group 2 of the periodic table, it has 2 valence electrons. Fluorine (F), found in Group 17, has 7 valence electrons.

Draw the Lewis symbols for each atom

Lewis symbols show the chemical symbol of an element and its valence electrons as dots. For Calcium (Ca), draw two dots around the "Ca" to represent its 2 valence electrons. For Fluorine, place 7 dots around the "F" symbol to represent its 7 valence electrons. The Lewis symbols should look like this: Ca: \[ \text{Ca} : \] F: \[ .\: .\: \text{F}\: . \]

Determine the type of bond that will form between the atoms

Calcium is a metal and Fluorine is a non-metal, so they will form an ionic bond. In an ionic bond, electrons are transferred from the metal (Ca) to the non-metal (F) until both reach a stable electron configuration. In the case of Calcium and Fluorine, Calcium will lose its 2 valence electrons to achieve a stable configuration (like a Noble gas with a full outer shell), and each Fluorine atom will gain 1 electron to achieve the same stable configuration.

Show the electron transfer using Lewis symbols

We shall show the transfer of electrons from Calcium to two Fluorine atoms. Once Calcium has lost its 2 valence electrons, it will become a positively charged ion with a +2 charge. Each Fluorine atom will gain 1 electron from Calcium and become a negatively charged ion (F⁻). The reaction could be represented like this using Lewis symbols: \[ \text{Ca} : \: +\: .\: .\: \text{F}\: . \: +\: .\: .\: \text{F}\: . \: \rightarrow \: [\text{Ca}]^{2+}\: +\: [\text{F}]\: -\: .\: .\: .\: . \: +\: [\text{F}]\: -\: .\: .\: .\: . \]

Write the final chemical formula for the compound

Now that we have represented the reaction using Lewis symbols, we can write the final chemical formula for the ionic compound that forms between Calcium and Fluorine: \( CaF_2 \) This is the formula for Calcium fluoride.

Key concepts

Valence Electrons

Valence electrons are the electrons sitting in the outermost shell of an atom. They play a crucial role in chemical bonding. For many elements, their chemical properties and reactivity largely depend on the number of valence electrons they possess. These electrons are involved in forming bonds with other atoms. For example, if you look at Calcium (Ca), it has two valence electrons. It is in Group 2 of the periodic table. On the other hand, Fluorine (F) has seven valence electrons and is found in Group 17.

When elements react, they either lose, gain, or share valence electrons to reach a more stable electronic configuration. This typically means having a full outer shell, similar to that of a Noble gas. Understanding how to identify and count valence electrons is a fundamental skill in studying chemistry and predicting how elements interact in ionic and covalent bonding.

Ionic Bonding

Ionic bonding occurs when electrons are transferred from one atom to another, leading to the formation of ions. This type of bonding typically happens between metals and non-metals. Metals, like Calcium in our example, tend to lose their valence electrons, whereas non-metals, such as Fluorine, tend to gain electrons. This movement of electrons allows each atom to achieve a full outer shell, leading to a stable structure.

The result is a metal that becomes positively charged due to the loss of electrons, and a non-metal that becomes negatively charged due to the gain of electrons. The positively and negatively charged ions attract each other, holding the compound together. This strong electrostatic attraction between the ions is what we refer to as an ionic bond. Additionally, ionic compounds often form crystal lattice structures due to such bonding.

Electron Transfer

Electron transfer is a vital concept in understanding ionic bonding. Simply put, it is the movement of electrons from one atom to another. In our example, Calcium transfers its two valence electrons to two Fluorine atoms. Why? To become more stable.

• The Calcium atom loses two electrons, transforming into a \([Ca]^{2+}\) cation.
• Each Fluorine atom gains one electron to form negatively charged \([F]^{-}\) anions.

This transfer ensures that both elements achieve a full outer electron shell, similar to the noble gases. The driving force behind this electron movement is achieving the lowest possible energy configuration, resulting in a more stable compound. By understanding electron transfer, we can predict the formation of ionic compounds and their resulting properties.

Chemical Formula

A chemical formula tells us the types and numbers of atoms in a molecule or compound. It is a shorthand representation of the compound's composition. In the case of the reaction between Calcium and Fluorine, the chemical formula is \(CaF_2\). This formula indicates that the compound, Calcium fluoride, is composed of one Calcium atom and two Fluorine atoms.

The numbers in a chemical formula are crucial as they show the ratio of the elements in the compound. The subscript 2 next to Fluorine signifies that two Fluorine atoms are needed to balance the charge of one Calcium atom. By using chemical formulas, chemists and students can easily understand the composition and proportions needed in chemical reactions, allowing for precise communication and understanding of chemical substances across different contexts.