Metals can be found in groups 1–13 on the periodic table and tend to have high melting and boiling points, conduct electricity, have low ionization energy, and have low electronegativity. Main group metals consist of groups 1 and 2 and parts of groups 13–16. Groups 1 and 2 metals have common characteristics.
An element (except hydrogen) in group 1 of the periodic table is an alkali metal. The alkali metals are lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). All group 1 elements contain one electron in their valence shell (outer electron orbital), which they tend to lose. Due to this, group 1 elements share common characteristics. They ionically bond with elements from group 17 to form compounds such as table salt (NaCl). Alkali metals react vigorously with oxygen and water. As you go down the alkali metal group, the elements become more reactive, and their melting points decrease. Rubidium is extremely reactive and is handled with caution due to its high reactivity. Alkali metals are generally soft to the touch. For example, it is possible to cut a block of sodium with a table knife. Rubidium and caesium have fewer commercial applications than other alkali metals.
Various compounds of lithium, sodium, and potassium are commonly found in nature. Rubidium, caesium, and francium are rarer in nature. Metallic lithium, sodium, and potassium and their various chemical compounds have multiple commercial applications and can be recovered from their compounds using electrochemical methods. For example, a Downs cell produces metallic sodium from molten sodium chloride. Molten sodium metal forms within the cell and is then recovered.
Downs Cell for Sodium Production
An element in group 2 of the periodic table is an alkaline earth metal. These are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra). All elements in group 2 contain two electrons in their valence shell, which they tend to lose to form compounds with elements from group 17. Oxides of these elements make alkaline solutions. These elements are also known to melt at extremely high temperatures. Alkaline earth metals are reactive, but not as reactive as alkali metals.
Beryllium is rare on Earth. Beryllium is commonly extracted from the mineral beryl using water and oxygen in a complex chemical process. Magnesium is abundant on Earth and is often alloyed with iron or aluminum and used as structural components found in cars and aircraft. Magnesium can be extracted from magnesium minerals. It can also be extracted from seawater using electrochemical methods.
Calcium is also very abundant in nature and is used in the production of steel and cement. Strontium is another element abundant on Earth that was widely used in cathode ray tubes (CRTs) and vacuum tubes. Barium is present in small percentages on Earth and seawater and is extracted from the mineral barite. Radium is the heaviest alkaline earth metal and is radioactive. Radium is found in uranium and thorium ores. Small amounts of radium are used in medicine.
Aluminum, found in group 13, is a soft metal with low density. Aluminum alloys are widely used as structural metals. Aluminum is utilized in construction and in packaging, such as production of aluminum cans. Electrochemistry is one method aluminum can be extracted from minerals. The mineral alumina (Al2O3) is dissolved in molten cryolite (Na3AlF6), which is another mineral. Molten metallic aluminum forms and settles at the bottom of the cell, the container where the process is taking place. The aluminum is then recovered. This process takes place at temperatures over 1,000°C and requires a lot of energy.
Hall-Héroult Process Cell for Aluminum Production
Many pure metals react with oxygen in the air and form metal oxides, resulting in corrosion. Some metals in the presence of air completely corrode. In some metals, the metal oxide forms a coating that diminishes contact between the metal and oxygen, which prevents corrosion. The process of making a material less reactive by coating it or letting the top layer react often with oxygen in the air is called passivation. Aluminum is an example of this phenomenon. When aluminum is in contact with oxygen gas, a layer of aluminum oxide (Al2O3), also known as alumina, forms on the metal. A thin layer of Al2O3 is enough to prevent contact of metallic aluminum and oxygen gas, which prevents further corrosion.