Problem 30 - Introductory Chemistry Atoms First

Question

Predict the chemical formula \(\mathrm{Na}_{\mathrm{}} \mathrm{O}_{y}\) of the compound that results from the reaction between the elements \(\mathrm{Na}\) and \(\mathrm{O}\). Answer: Na is a group IA metal and thus loses one electron to become \(\mathrm{Na}^{+} . \mathrm{O}\) is a group VIA nonmetal and so gains two electrons to become \(\mathrm{O}^{2-} .\) In order for the compound formed to be electrically neutral, the formula must be \(\mathrm{Na}_{2} \mathrm{O}\).

Step-by-Step Solution

Answer

The chemical formula of the compound formed by the reaction between sodium and oxygen is \(Na_2O\).

Step 1: 1. Identify the charge of each element and its electronic basis

Sodium (Na) is an alkali metal in Group IA and has one valence electron. Metals in Group IA tend to lose one electron to have a stable electron configuration, thus forming cations with a charge of +1 (Na⁺). Oxygen (O) is a non-metal in Group VIA and has six valence electrons. Elements in Group VIA need two more electrons to achieve a stable configuration, forming anions with a charge of -2 (O²⁻).

Step 2: 2. Determine the ratio necessary for the compound to be electrically neutral

In order to form an electrically neutral compound, the total positive charge and the total negative charge must balance each other out. In this case, we need two Na⁺ ions (each with a +1 charge) to balance out a single O²⁻ ion (with a -2 charge).

Step 3: 3. Write the chemical formula

To reflect the balance of charges, the chemical formula for the compound formed by Na and O should be Na₂O. This means that two sodium atoms react with one oxygen atom to create an electrically neutral compound. Answer: The chemical formula of the compound formed by the reaction between sodium and oxygen is Na₂O.

Key Concepts

Ionic Compounds

Ionic compounds are formed through the transfer of electrons from one atom to another, creating ions. This typically occurs between metals and non-metals. The metal, which loses electrons, forms a positively charged ion known as a cation. The non-metal, which gains electrons, becomes a negatively charged ion called an anion. When these oppositely charged ions come together, they form an ionic bond. This bond is the result of electrostatic attraction, which holds the ions together in a stable structure.

• An example is sodium oxide (\(\mathrm{Na}_2\mathrm{O}\)), where sodium cations (\(\mathrm{Na}^{+}\)) bond with an oxygen anion (\(\mathrm{O}^{2-}\)).

The overall compound is electrically neutral, meaning the total positive charge equals the total negative charge. This balance is crucial for the formation of any stable ionic compound.

Alkali Metals

Alkali metals belong to Group IA of the periodic table and include elements like lithium, sodium, and potassium. These metals are known for their high reactivity, especially with non-metals such as oxygen and halogens. The high reactivity of alkali metals stems from their single valence electron.

• This lone electron is relatively weakly bound to the atom and is easily lost in chemical reactions.

This loss of an electron results in the formation of a cation with a +1 charge. This is why sodium (\(\mathrm{Na}\)) readily forms the sodium ion (\(\mathrm{Na}^{+}\)) during reactions. The ease with which alkali metals lose their electron makes them prominent players in the formation of ionic compounds, providing the positive charge needed to balance the negative charge of anions.

Electron Configuration

Electron configuration is a way to denote the arrangement of electrons in an atom's electron shells. The configuration follows the order of the periodic table and the principle of minimizing energy levels. Electrons fill orbitals starting with the lowest energy levels. For example, sodium's electron configuration is \[1s^2 2s^2 2p^6 3s^1\]. This shows that sodium has a single electron in its outermost shell, which it can lose to become stable, forming a \(\mathrm{Na}^{+}\) ion. Oxygen, on the other hand, has the electron configuration \[1s^2 2s^2 2p^4\] and needs two more electrons to fill its outer shell. By gaining these electrons, oxygen becomes \(\mathrm{O}^{2-}\), completing the octet in the \(\mathrm{2p}\) orbital. This completion represents a stable electron configuration, explaining why oxygen acts as an anion in reactions.

Chemical Reactions

Chemical reactions involve the rearrangement of atoms or ions to form new substances. A common form of chemical reaction is the interaction between alkali metals and non-metals, resulting in the formation of ionic compounds. In the case of sodium and oxygen, sodium loses its outermost electron to oxygen in a direct transfer.

• This reaction results in sodium oxidizing, which means it loses electrons.
• Oxygen, on the other hand, gets reduced by gaining electrons.

In broader terms, oxidation refers to the loss of electrons, while reduction refers to the gain of electrons. These simultaneous processes are called redox reactions. In every chemical reaction, keeping track of the movement of electrons is crucial for predicting the compound's chemical formula. For \(\mathrm{Na}_2\mathrm{O}\), two sodium atoms each donate an electron to an oxygen atom, creating a stable and neutral compound. Chemical reactions thus allow for the transformation of substances into new materials with different properties.