Where did all the elements go? Many were taken away just for convenience sake, as this page talks on Common Ion Colors or frequently seen ion colors. But first off, explaining what an ion is. An ion is when an atom either gains or loses an electron. This is denoted by the subscript number. If the atom lost an electron, it becomes a positive ion, or a Cation. If the atom gains an electron, it becomes a negative ion, or an Anion. Different ions will have distinct colors when in a solution. Many times, it is useful to know what these colors are, so listed are common ion colors!
If you remember from before with electron configurations, transition metals have electrons in the D orbital which is in a lower energy level. These electrons, since they are not in the outer energy level, are not considered valence electrons. But, when it comes to ions, sometimes electrons from that orbital can affect the ion charge. Hence, you see some with 2+ and 3+ charge like Iron. D orbital electrons are also the reason why the transition metals, despite having the same number of valence electrons, can have very different properties such as the color of its ionic solution.
In no way shape or form am I saying that these are the only ions that exist. This is just a brief list of simplistic, monatomic ions. There are many other common ions that aren't monatomic, but those are not listed here.