Periodic Table Basics: Electrons, Ions, and Atomic Numbers Explained

The periodic table organizes elements by their atomic number, which represents the number of protons in an atom's nucleus.Let's look at hydrogen, the simplest element with atomic number one.In hydrogen, a single proton in the nucleus defines its atomic number, and one electron orbits around it.Now let's examine oxygen, which has atomic number eight.Oxygen has eight protons in its nucleus, and eight electrons orbiting in multiple shells.In a neutral atom, the number of protons equals the number of electrons, creating a balanced electrical charge.This balance of positive protons and negative electrons results in an overall neutral charge.These electrons arrange themselves in specific shells around the nucleus, which we'll explore in more detail next.Electrons arrange themselves in shells around the nucleus, with each shell having a specific maximum capacity.The first shell can hold up to two electrons.The second shell has a maximum capacity of eight electrons.The third shell can accommodate up to eighteen electrons, though we're showing just eight here for clarity.Elements in the same group of the periodic table share similar electron configurations in their outer shell.Let's look at Group 1, the alkali metals. These elements all have one electron in their outer shell.This similar outer shell configuration explains why these elements share comparable chemical properties.Because they all have one electron in their outer shell, these elements tend to react in similar ways with other elements.When atoms gain or lose electrons, they become charged particles called ions.Sodium tends to lose an electron, becoming a positive ion called a cation.Chlorine readily accepts this electron, becoming a negative ion called an anion.Let's compare the two types of ions. Cations are positively charged ions that have lost electrons, while anions are negatively charged ions that have gained electrons.The opposite charges of these ions create an attractive force, leading to ionic bonding. This is how sodium and chlorine combine to form sodium chloride, or table salt.