Properties of Matter for Select Elements
by: Emory Grace Edwards
My three familiar elements on the periodic table are calcium (Ca), copper (Cu), and oxygen (O). My three unfamiliar elements on the periodic table are magnesium (Mg), cobalt (Co), and boron (B).
Density (lowest to highest): Oxygen (1460), Calcium (1530), Magnesium (1736), Boron (2466), Cobalt (8800), Copper (8933)
Melting point (lowest to highest): Oxygen (-218.79*C), Magnesium (650*C), Calcium (842*C), Copper (1084.62*C), Cobalt (1495*C), Boron (2077*C)
Calcium- Calcium metal is used as a reducing agent in preparing other metals, and as an alloying agent for aluminium, beryllium, copper, lead and magnesium alloys.
Cobalt- Cobalt metal is used in electroplating because of its attractive appearance, hardness and resistance to oxidation. Radioactive cobalt-60 is used in the treatment of cancer and, in some countries, to irradiate food to preserve it.
Copper- Historically, copper was the first metal to be worked by people, and the discovery that it could be hardened with a little tin to form the alloy bronze gave its name to the Bronze Age. Copper sulfate is used widely as an agricultural poison and as an algicide in water purification.
Oxygen- The greatest commercial use of gaseous oxygen is in the steel industry. Large quantities are also used in the manufacture of epoxyethane, nitric acid, hydrogen peroxide and chloroethene, the precursor to PVC and for oxy-acetylene welding and cutting of metals.
Boron- Amorphous boron is used in pyrotechnic flares to provide a distinctive green colour, and in rockets as an igniter. The most important compounds of boron are boric (or boracic) acid, widely used as a mild antiseptic, and borax which serves as a cleansing flux in welding and as a water softener in washing powders.
Magnesium- Magnesium is used in flares, pyrotechnics and incendiary bombs and was formerly used in flash bulbs. As it is one-third less dense than aluminium, its alloys are useful in aeroplane and missile construction and in alloys to provide lightweight frames for bicycles, car seats and luggage.
Calcium- Calcium is the fifth most abundant metal in the Earth’s crust, greater than 3% by mass. It is not found uncombined in nature, but occurs abundantly as limestone. Calcium is prepared commercially by the electrolysis of fused calcium chloride to which calcium fluoride is added to lower the melting point.
Cobalt- Cobalt is found in the minerals cobaltite, smaltite and erythrite. Important ore deposits are found in Zaire, Morocco and Canada. A huge reserve of several transition metals (including cobalt) can be found in strange nodules on the floors of the deepest oceans. The nodules are manganese minerals that take millions of years to form, and there are many tonnes of cobalt present in this form.
Copper- Copper is an essential element, an adult human need to ingest around 1.2 milligrams of copper a day to help enzymes transfer energy in cells. Excess copper is toxic and genetic diseases such as Wilson’s disease and Menke’s disease are caused by the body’s inability to utilise copper properly.
Oxygen- Oxygen, as a gaseous element, forms 21% of the atmosphere by volume, which is half-way between 17% (below which breathing for unaclimatised people becomes difficult) and 25% (above which many organic compounds are highly flammable). The element and its compounds make up 49.2%, by mass of the Earth’s crust, about two-thirds of the human body and nine-tenths of water.
Boron- Elemental boron is not considered a poison, and indeed is essential to plants, but assimilation of its compounds has a cumulative toxic effect. Boron is an essential mineral for plants but not animals - in fact it can be toxic in excess. We take in about 2 milligrams each day from our food (about 60 grams in a lifetime). Some boron compounds show promise in treating arthritis.
Magnesium- Magnesium is an essential element in both plant and animal life. It is non-toxic. Chlorophylls are magnesium-centred porphyrins, so, without magnesium, photosynthesis, and therefore life as we know it, would not exist. Humans take in 250-350 milligrams each day (about 100 grams a year), and we each have about 20 grams in our bodies. Magnesium hydoxide (milk of magnesia), sulphate (Epsom salts), chloride and citrate are used in medicine.