Question

Predict the formula of the compound that forms when sodium atoms react with sulfur atoms. Completely explain your reasoning.

Short answer

The formula of the compound that forms when sodium atoms react with sulfur atoms is \(Na_2S\). This is because sodium (Na) has 1 valence electron and wants to lose it, while sulfur (S) has 6 valence electrons and wants to gain 2 to achieve a full outer shell. Therefore, 2 sodium atoms combine with 1 sulfur atom to satisfy the octet rule.

Step-by-step solution

Identify the valence electrons of sodium and sulfur

First, we need to identify the number of valence electrons in sodium (Na) and sulfur (S) atoms. The valence electrons can be found in the outermost shell of an atom. Sodium is in Group 1 of the periodic table, meaning it has 1 valence electron. Sulfur is in Group 16, meaning it has 6 valence electrons.

Apply the octet rule

The octet rule states that elements will lose, gain, or share electrons in order to achieve a full outer shell of 8 electrons. In this case, sodium has 1 valence electron in its outer shell, while sulfur has 6. Sodium will want to lose its 1 valence electron to have a stable configuration, while sulfur will want to gain 2 electrons to achieve a stable configuration with 8 valence electrons.

Determine the ratio of sodium to sulfur atoms

To form a stable compound, we need to find the ratio in which sodium and sulfur atoms combine to satisfy the octet rule. Sodium wants to lose 1 electron, while sulfur wants to gain 2 electrons. Therefore, it will take 2 sodium atoms each losing 1 electron to provide the 2 electrons needed by the sulfur atom. So, the ratio will be 2 sodium atoms to 1 sulfur atom.

Write the formula of the compound

Considering the ratio found in step 3, we can now write the formula for the compound formed by sodium and sulfur. As 2 sodium atoms combine with 1 sulfur atom, the formula of the compound will be Na2S.

Final Answer:

The formula of the compound that forms when sodium atoms react with sulfur atoms is \(Na_2S\).

Key concepts

Valence Electrons

Valence electrons are the electrons located in the outermost shell of an atom. They play a crucial role in determining how an element will react with others, because these are the electrons that can be lost, gained, or shared in chemical reactions. For example, sodium (Na) is found in Group 1 of the periodic table and possesses one valence electron, which is willing to lose to achieve a stable configuration.

In contrast, sulfur (S), located in Group 16, has six valence electrons, leaving it two electrons shy of achieving the 'octet', a state where its valence shell is considered stable. Understanding the number of valence electrons in an element not only helps predict how it will react but also determines the type of ion it will form. Knowing this, we can start to visualize how elements will combine to form compounds.

Octet Rule

The octet rule is a chemical rule of thumb that reflects observation that elements tend to combine in such a way that each atom has eight electrons in its valence shell, giving it the same electron configuration as a noble gas. The rule is based on the principle that a full valence shell is the most stable electron configuration.

When applying the octet rule, we see that atoms will lose, gain, or share electrons to fill their outermost shell with eight valence electrons. Sodium, for example, finds it easiest to lose one electron, achieving the electron configuration of neon, while sulfur aims to gain two electrons to emulate the configuration of argon. Through the application of the octet rule, predicting the resulting formula during compound formation becomes a structured process.

Compound Formation

Compound formation is the result of chemical reactions where two or more elements combine to form a new substance with unique properties. The bonds forming in compounds can be ionic or covalent, based on the nature of the interaction between valence electrons of the reacting atoms.

In the example of the reaction between sodium and sulfur, an ionic compound forms as sodium, a metal, loses an electron to become a positively charged ion, while sulfur, a non-metal, gains electrons to become negatively charged. The opposite charges of these ions lead to a strong ionic bond. The whole process of compound formation involves balancing these charges to result in a neutral compound, which is what the chemical formula reflects.

Reaction of Sodium with Sulfur

During the reaction of sodium with sulfur, each sodium atom loses one electron to form a sodium ion with a positive charge (Na+). Sulfur, which needs two electrons to complete its octet, gains two electrons to form a sulfide ion with a negative charge (S2-).

As a result of this electron transfer, two sodium ions are needed for every sulfide ion to balance the charges and achieve a stable, electrically neutral compound. This is why the chemical formula of the compound resulting from the combination of sodium and sulfur is Na2S, indicating that two sodium atoms combine with a single sulfur atom. Understanding this reaction showcases not only the transformative nature of chemical bonding but also the predictability of compound formation based on the behavior of valence electrons and the octet rule.