Identifying Types of Elements - High School Chemistry

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.

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.

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.

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.

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.

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

Elements on the right section of the periodic table are non-metals. The first two columns of the periodic table are the alkali metals and the alkaline earth metals, respectively. Groups 3-12 are the transition metals (except the lanthanide and actinide series). The "stairway" from the top left of the p-block to the bottom right of the p-block are the metalloids, which include boron, silicon, germanium, arsenic, antimony, tellurium, and polonium. The remainder of the elements are nonmetals, which include the halogens and noble gasses in groups 7 and 8, respectively.

Alkali metals are extremely reactive with water. Metals are generally shiny and good conductors of electricity. Noble gases are all gases. Halogens are mostly gases or liquids. Non-metals, however, are generally solid, dull, brittle, not conductive of electricity, and not reactive with water.

The correct answer is hydrogen. While it's misleading that hydrogen is located on the left hand side of the periodic table with the rest of the metals, it is actually not characterized as a metal. The main reason why hydrogen is listed as a group 1 element is due to its electron configuration.

Hydrogen would not be considered a metal due to the following reasons:

1. It will not readily form cations as the rest of the group 1 elements.

2. When in its elemental form, hydrogen is in its diatomic stage as . This is also seen with elements such as nitrogen and oxygen, which are also nonmetals.

3. It will form covalent bonds, unlike metals. Metals are known to commonly form ionic bonds.

4. It will form hydride ions. It is extremely rare to see group one elements do the same.

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.

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.

Noble gases are naturally occurring elements that already have eight electrons in their outer shell. Chemical reactions typically occur because atoms are following the octet rule. Since noble gases already have eight electrons in the outer shell, they are less likely to react.

This is a knowledge based question. The incorrect answers are all true facts about Halogens. Halogens are very reactive because they have seven electrons in their outer shell. Atoms that are closer to achieving the Octet rule are more reactive.

Transition metals are unique because they have valence electrons in different shells. Transition metals have several different oxidation states and can react in a variety of ways because of how their valence electrons are arranged. All alkali only have one valence electron.