Question

Draw the Lewis dot symbols for the atoms Al and O. Use the Lewis model to determine the formula for the compound formed from these two atoms.

Short answer

Lewis dot symbol for Al has three dots and O has six dots. Al loses three electrons to form Al³⁺ and O gains 2 electrons to form O²⁻, resulting in the compound Al₂O₃.

Step-by-step solution

Determine Electron Configuration

First, we need to find the electron configuration of aluminum (Al) and oxygen (O). Aluminum has an atomic number of 13, so its electron configuration is 1s² 2s² 2p⁶ 3s² 3p¹, which means it has 3 valence electrons. Oxygen has an atomic number of 8, so its electron configuration is 1s² 2s² 2p⁴, which means it has 6 valence electrons.

Draw Lewis Dot Symbols

Now draw the Lewis dot symbols for each element based on their valence electrons. Put one dot for each valence electron around the symbol for the element:- For Al, place three dots around the symbol (one for each valence electron)- For O, place six dots around the symbol in pairs to represent the 6 valence electrons.

Determine Ionic Bonding

In the Lewis model, atoms tend to form bonds to achieve a noble gas electron configuration. For Al, giving up 3 electrons to have a full 2nd-energy level shell makes sense. For O, gaining 2 electrons to have a full 2nd-energy level shell is favorable.

Predict the Compound Formula

Since Al needs to lose 3 electrons and each O atom needs to gain 2 electrons, two Al atoms can provide a total of 6 electrons, which three O atoms will need (each needing 2 electrons). Hence, the formula of the compound formed will be Al₂O₃.

Key concepts

Electron Configuration

Understanding the electron configuration of an atom is crucial for predicting how it will bond with other atoms. The electron configuration describes the distribution of electrons in an atom's orbitals, which are the regions around the nucleus where electrons are most likely to be found. For example, aluminum (Al) has an atomic number of 13, meaning it has 13 electrons that need to be arranged in its orbitals. Its configuration is written as 1s² 2s² 2p⁶ 3s² 3p¹.

This notation indicates that the innermost shell (the 1s orbital) is filled with 2 electrons, followed by the 2s orbital with 2 electrons, and the 2p orbital also being completely filled with 6 electrons. The third shell begins with the 3s orbital, holding 2 electrons, and has a single electron in the 3p orbital. This arrangement is foundational for understanding how atoms will interact with each other in bonding scenarios.

Valence Electrons

Valence electrons are the outermost electrons of an atom and are paramount in determining how an atom will bond with others. They are the electrons that participate in chemical reactions and form bonds. In our example with aluminum, we identify that it has 3 valence electrons in the outer shell (3s² 3p¹). Oxygen, on the other hand, has a total of 6 valence electrons (2s² 2p⁴).

When drawing the Lewis dot symbols for these atoms, we visually represent these valence electrons by placing dots around the element's symbol. The number of dots matches the number of valence electrons. These symbols serve as a visual aid to predict how atoms might bond. In ionic compounds, atoms will lose or gain electrons to achieve a more stable electron configuration, often mimicking the electron configuration of the nearest noble gas.

Ionic Bonding

Ionic bonding occurs when atoms transfer electrons between each other, creating ions that are electrically charged. Atoms with fewer valence electrons, such as aluminum with its three valence electrons, tend to lose them and become positively charged ions called cations. Conversely, atoms like oxygen with six valence electrons, tend to gain additional electrons to fill their outer shell, becoming negatively charged ions known as anions.

In the compound that arises from the bonding of Al and O, we observe this transfer of electrons: each aluminum atom loses three electrons becoming Al³⁺, while each oxygen atom gains two electrons to become O²⁻. The resulting compound, which is electrically neutral overall, has to balance both the charges and the number of electrons lost and gained. Following this principle, we deduce that the formula for the compound formed between aluminum and oxygen is Al₂O₃, indicating that the compound consists of two aluminum ions and three oxide ions.