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

Understanding the electron configurations of elements is essential for predicting how atoms will interact and bond with each other. An atom's electron configuration outlines the distribution of electrons in its atomic orbitals and is strongly tied to the element's properties. For aluminum (Al), with an atomic number of 13, its electrons are arranged in the orbitals in the following manner: the first two electrons fill the 1s orbital, the next two fill the 2s orbital, followed by six electrons in the 2p orbitals, and the remaining three occupy the 3s and 3p orbitals. This configuration is often written as 1s² 2s² 2p⁶ 3s² 3p¹. Similarly, oxygen (O), with an atomic number of 8, has its electrons arranged as 1s² 2s² 2p⁴.

The significance of knowing these configurations lies in the role the outermost electrons play in chemical bonding. For instance, Al's three outermost electrons (3s² 3p¹) can be removed more easily than the ones in completed shells, making it more likely to participate in bonding through electron transfer.

Valence electrons are the outermost electrons of an atom and are fundamental in determining how an element will react chemically. They are responsible for the formation of chemical bonds, as atoms interact to achieve a more stable electron configuration, often resembling that of a noble gas. For example, aluminum's (Al) valence electrons are the three electrons in the 3s and 3p orbitals. Oxygen (O) has six valence electrons residing in the 2s and 2p orbitals.

When drawing Lewis symbols, these valence electrons are represented as dots around the element's symbol. Such visualizations help predict the bonding behaviour of the elements: aluminum, with its three valence electrons, tends to lose electrons, whereas oxygen, with six valence electrons, tends to gain electrons to achieve stability. This guides us towards understanding the nature of the bond that will form between the two elements.

The determination of the chemical formula for a compound involves understanding how atoms combine based on their valence electrons to achieve full outer shells. Using Lewis symbols, we can visualize the transfer or sharing of electrons between atoms to form molecules or ionic compounds. For the compound that forms from aluminum (Al) and oxygen (O), the process begins with recognizing that Al can lose its three valence electrons and O needs two to achieve a stable octet similar to noble gases.

The ratio of Al to O required for stability is determined by balancing the transfer of electrons. Since each Al can give up three electrons and each O needs two, two Al atoms will completely transfer their six electrons to three O atoms, resulting in the chemical formula Al₂O₃. This stoichiometry reflects a stable compound where the total number of electrons lost by aluminum equals the number gained by oxygen, fulfilling the octet rule for all atoms involved.