A potassium ion is known as a cation because it has a positive charge. The charge is determined by looking at the periodic table. Potassium falls under Group 1 on the periodic table, otherwise known as the alkali metals. The charge of an element can be determined by its valence electrons, or the electrons in the s and p orbitals in the farthest electron shell. Using the shorthand electron configuration on Potassium [Ar]2s1 , it is obvious that there is one valence electron. Looking at trends of electronegativity and ionization energy, we see that atoms in group one have the lowest electronegativity and ionization energy. Electronegativity and ionization increase as you move from left to right or bottom to top. This means that it is more likely to lose its valence electron than it is to gain more. Their goal is to either reach zero or eight electrons. Because it will lose its one valence electron to Oxygen we can view it as K plus one. An Oxygen ion is known as an anion because it has a negative charge. It’s charge can also be determined by looking at the periodic table. When looking at the shorthand electron configuration for Oxygen , [He]2s22p4, it is obvious that there are 6 valence electrons. In addition, Oxygen falls under Group 6 on the periodic table. This also means that Oxygen has a high electronegativity and ionization energy. Oxygen is more likely going to take 2 valence electrons than lose 6. Oxygen can now be viewed as O two minus. Now comes bonding. The Oxygen ion will take the Potassium ions one valence electron. This leaves the Potassium with a neutral charge; however, the Oxygen ion still has a charge of one plus. This can be solved by adding in another Potassium ion. Now all atoms have a neutral charge. So why were arrows used? Arrows were used to show that in ionic bonding, electrons are leaving the element. In a covalent bond, the atoms would be written next to each other signifying that they shared electrons. Since these electrons are taken, rather than shared, arrows are used to show that the electrons are forcibly taken. This results in our compound, Potassium Oxide.