24th June 1802 – Strontium in Toothpaste?
One effect of nuclear fission radiation is contamination with Sr-90 one of the strontium radioisotopes. However this deadly ‘bone-finder’ has its medical uses in radio-therapy.
But with strontium, as with other elements, a great chemical difference exists between the isotopes and the individual element which is so reactive with oxygen and water it is only found in compounds.
See Addendum if you want to find out more of the science. Why not?
Many early chemists were also physicians, as was the case with another local hero, chemist and physician, William Cruickshank, who Today in 1802 became a Fellow of the Royal Society.
It was Cruickshank, along with Adair Crawford, also a physician, who were the first to be credited in recognising the alkaline earth metal, strontium, found in the local lead ores in 1790.
Crawford whilst working with Barium, recognised that this new substance, later named ‘strontium’ had different properties than normally seen in ‘heavy spars’. It was to be named strontites by Thomas Charles Hope in 1793, after the village of Strontian in Argyll.
It was in 1808 that Humphry [no ‘e’] Davy reported to the Royal Society on June 30th his findings on isolating the element. In keeping with naming of other alkaline earths it was renamed Strontium (Sr) and is the 15th most abundant element.
Strontium, which imparts a reddening colour to a flame, has many applications, including fireworks, and strontium-based products were to be developed in the 19th century, by the Albright and Wilson Company, such as the salt Strontium Chloride (Sr Cl2).
This along with strontium acetate is used in toothpaste for sensitive teeth and strontium salts are said to have improving effects on osteoporosis as their composition and absorption in the body, is similar to calcium.
Albright and Wilson, now defunct, was once second only to the giant but now late, Imperial Chemical Industries (ICI), had expanded into silicones, and detergents and chromium as well as strontium-based products in the 19th century.
Ref: chemguide.co.uk./Group 2
Ref: Oxford Dictionary of National Biography. Vol 14 519-20.
Ref:Periodic Table/Interactive P.T. of the elements. About.Com Chemistry.
Tomorrow’s Post looks at 19th century Christian dissent and persecution.
It was Humphry Davy in 1807 who isolated the elements of the alkaline earth metals: Beryllium (Be), magnesium (Mg), (recognised as an element by Joseph Black in 1775); calcium (Ca), strontium (Sr), barium (Ba) and Radium (Ra).
Alkaline Earth Metals are found in Group 2 (second column) of the Periodic Table, having 2 electrons in the outside or valence shell of the atom. These are not tightly bound so lose electrons to bond with other elements to form compounds.
They possess many of the properties of metals and all have the second lowest electro-negativity: Group 1 has the lowest: Group 7 has the highest. Alkaline Earth Metals have oxidation of +2 making them very reactive.
Oxidation is the reaction with Oxygen, causing the element being oxidised to give up its electrons causing rusting, (slow oxidation), or burning (rapid oxidation).
Group 2 are silvery metals with a higher melting and boiling point and are less reactive than Group 1, as it is more difficult to lose 2 electrons than 1. Reacting with water-as with Group 1 metals-they form an alkaline solution with reaction increasing going down the Group due to the increasing size of the atom.
As with Group 1 (Alkali Metals), the atomic radius increases going down the column. So Beryllium (at the top), is a small atom, the size governed by the number of shells or layers around the nucleus as well as the pull on the electrons by the nucleus.
Melting/boiling points decreases going down the Group, (say between Magnesium and Calcium), due to weaker forces of attraction between atoms so hardness increases.
The number of Energy Levels or Shells around the nucleus increases going down the Groups. So in Group 2, beryllium has energy level of 2 ( n=2) as it is in row/period two of Periodic Table and Radium has energy level of 7 (n=7.) as it is down at row seven.
Reactivity is the ability of an atom to gain a full outside shell to gain stability (normally Octet Rule). So those in group 1 will easily lose its sole electron (in the outer shell), and at the other end of the Periodic Table ( Fluorine with 7 electrons (Group 7) will react with anything.
Isotope from the Greek (same place) as they all have same place in P.T. as their natural element. Isotopes have different mass number. They have the same number of protons but different number of nucleons (protons and neutrons) in the nucleus.
Strontium-90 has in its nucleon: 52 neutrons and 38 protons: a Mass 87.62 and Atomic Number of 38.
Electronegativity: (Symbol x) is the power of an atom to attract electrons.
Tags: Adair Crawford, Alkaline Earth metals, Allbright and Wilson, Barium, Fireworks, Imperial Chemical Industries, Reactive, Sensodyne Toothpaste, Strontian, Strontianite, Strontite, Strontium, Thomas Charles Hope, William Cruickshank