All elements will form ions if you force it (meaning if use man power (actually machine power) to ionize it) But elements that don't usually form ions are ones that are already satisfied with the number of electrons they have. Ever heard of the octet rule? (If not, message board me, or Google it). Elements that satisfy the octet rule are "happy" and don't want to ionize (form ions). These elements are the group 18 elements (or group 8A, depending on your Periodic Table) and are called the noble gases. Helium (He) is a noble gas that does not ionize as well. But notice it only has 2 electrons. That's fine, because Helium only wants 2 electrons in order to fill is 1s subshell. One additional note, noble gases are known as inert gases because they rarely react to form compounds.
Ionic bonds are formed between metals and nonmetals. Therefore, almost any element can form ionic bonds.
However, since carbon's electron configuration is such that it can accommodate four covalent bonds, it forms covalent bonds very readily. Therefore, it is never seen in ionic compounds.
A molecule consists of two covalently bonded atoms. A covalent bond consists of two nonmetals.
Neon group elements does not tend to form ions at all.They are in stable state and do not form ions.
These are the noble gases.
iron
Group that tend to form -1 ions include group VIIA
Metals tend to form positive ions.
They can form ionic compounds with halogens.
On the periodic table, Groups 4 - 7 tend to form negative ions. These groups tend to gain electrons, thus forming negative ions.
Why does group 4A elements tend to form covalent bonds rather than ionic bonds? 
Group that tend to form -1 ions include group VIIA
Metals tend to form positive ions.
They can form ionic compounds with halogens.
On the periodic table, Groups 4 - 7 tend to form negative ions. These groups tend to gain electrons, thus forming negative ions.
Group one, not including element 1 (helium) tend to form ions.
Why does group 4A elements tend to form covalent bonds rather than ionic bonds? 
Alkali metals group tends to form ions.They give single electron to gain positive charge.For example : Sodium give one electron to become Na+ ion.
elements of group 6 - colloum 10 gain 2 valence electrons when they form ionic bonds
Metals tend to form positive ions also known as cations.
The Group 2 elements, or the Alkali Earth metals, tend to form +2 charges when they become ions. This is because Group 2 metals have 2 valence electrons and it is easier to lose 2 electrons than it is to gain 6 electrons to form a full outer shell.
Nonmetals tend to attract electrons to become negative ions.
The transition metals tend to form colored compounds.