Metals can be found on the left side and center of the periodic table. Because of their generally small number of valence electrons, they prefer to lose their valence electrons, resulting in positively charged ions.

Some examples are the alkali metals and alkaline earth metals, which form and ions, respectively. Transition metals vary, but will usually form ions between and .

In contrast, non-metals (such as the halogens) will usually form negative ions.

In general, metals are found to the left of the periodic table and non-metals are found to the right. Group 1 holds the alkali metals and group 2 holds the alkaline earth metals. Groups 3-12 are considered the transition metals.  Groups 12-16 contain non-metals and metalloids. Elements in group 17 are known as the halogens, and elements of group 18 are known as the noble gases.

Elements in a given group will all have the same valence electron configuration, giving them similar chemical properties. For example, the alkaline earth metals form stable ions with a positive two charge, are somewhat reactive with water, and commonly form stable oxides.

In general, metals are found to the left of the periodic table and non-metals are found to the right. Group 1 holds the alkali metals and group 2 holds the alkaline earth metals. Groups 3-12 are considered the transition metals.  Groups 12-16 contain non-metals and metalloids. Elements in group 17 are known as the halogens, and elements of group 18 are known as the noble gases.

Elements in a given group will all have the same valence electron configuration, giving them similar chemical properties. For example, the halogens are very electronegative and are most stable in the negative one oxidation state.

Group 1 elements are known as the alkali metals, and include lithium, sodium, potassium, rubidium, and cesium. These elements have only one valence electron, giving them extremely low ionization energies. When in contact with water, these elements for alkali metal hydroxides and release hydrogen gas. The heat from the reaction can ignite the hydrogen, causing the explosion characteristic of these reactions.

Group 18 in the periodic table contains the noble gases. These elements contain full s orbitals (2 electrons) and full p orbitals (6 electrons), giving each noble gas a total of eight valence electrons. Since the noble gases have complete octets in their ground states, they have extremely high ionization energies and extremely low electronegativities. Essentially, it requires a very large amount of energy to remove an electron from a noble gas (ionization energy), and there is virtually zero attraction between these elements and the electrons of other nearby atoms (electronegativity).

Groups 3-12 on the periodic table contain the transition metals. These elements are characterized by partially filled d orbitals. Since the d orbitals are so large, electrons are able to shift around within subshells and flow between atoms to generate multiple oxidation states for these elements. For example, iron is an element in group 8 and commonly exists in either of two oxidation states: iron (II) or iron (III).

Group 1 elements will always have an oxidation state of , group 2 elements will always be , and group 17 elements will always be . Group 18 holds the transition metals, which generally have an oxidation state of zero.

The lanthanides and actinides are generally separated from the periodic table to facilitate formatting. These regions of the periodic table are characterized by the presence of f orbitals, which can carry up to fourteen electrons. The actinides are one period below the lanthanides, meaning that they already contain a complete 4f orbital. Electrons in the actinide region are distributed between the 5f, 6d, and 7s orbitals in the configuration that generates the greatest stability.

Because the orbitals are so large in this region and nuclei contain so many particles, the actinides are generally somewhat unstable and contain radioactive nuclei. Cerium is a lanthanide, found one period above the actinides. The atomic masses of the actinides range from approximately 227amu to 262amu. Group 16 contains elements such as oxygen and silicon, and is not associated with the actinides.

Metalloids are classified as elements with properties of both metals and nonmetals. Of these choices, Aluminium is the only one that is not a metalloid; it is actually a metal.

Diatomic elements are elements with two atoms in one molecule. Of these choices, helium cannot be diatomic, as it is a noble gas and has no valence electrons that are free to bond due to its full outer shell.

Only oxygen, hydrogen, nitrogen, fluorine, and chlorine can bond with itself to form gas. Noble gases, elements in the last column, do not bond with themselves to be able to form gas molecules since their valence shells have full octets of electrons.