Electrons are found in clouds or orbits around the nucleus of the atom and that each orbit has a specific number of electrons that it can hold, 2 in the first, 8 in the second, and 8 in the third. When these orbits are full the electrons are stable. In this problem we see that element X has an atomic number of 11. Using the 2–8–8 rule it shows that there is only one electron in the third orbit, making it unstable and making this electron easy to donate to another atom. Element Y has 9 electrons and this means that the second orbit, which needs 8 to be stable, only has 7 electrons and is ready to receive an electron. Therefore binding will occur with element X donating the single electron in its third orbit to stabilize the second orbit of element Y.
The building blocks of proteins are amino acids. These are connected by a peptide bond which forms between the carboxyl group of one amino acid and the amino group of a second amino acid. The peptide bond is one of the strongest covalent bonds.
Spheres of hydration keep solutes in solution in water and this is important for normal functioning of biological systems as key components such as proteins and nucleic acids work only in solution. An example of how spheres of hydration work is seen when salt is mixed with water. The salt dissolves as spheres of hydration form around each of the components of salt, sodium and chloride. Sodium has a positive charge which attracts the negative side of the polar molecule of water, and chloride has a negative charge that attracts the positive polar side of water. These attractions surround each of the ions and keep them separated as ions. As the salt concentration reaches its saturation point, it will recrystallize. This occurs because there is not enough water to surround the ions.