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.

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.

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.

Groups 3 to 12 on the periodic table contain all of the transition metals. Any elements found outside of these groups is not a transition metal. Transition metals have a partial amount of the d subshell filled with electrons.

This problem is one that can be quickly answered by looking at a periodic table of the elements. Carbon, nitrogen, oxygen, phosphorus, sulfur, selenium are all nonmetals. The other options are incorrect as they reference other classes of elements.

Noble gases are the elements in group 18 of the periodic table. They are called noble gases because their electron shells contain a stable valence octet. This causes them to be stable, have extremely high ionization energies, and no electronegativities. Since the atoms of noble gases already have complete valence octets, they do not readily donate or accept electrons from other elements. This means they will not easily form bonds or participate in chemical reactions.

To find the number of neutrons take the atomic mass of each element and subtract it by the atomic number. For neon this is:

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.

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.