Maria Sklodowska-Curie (1867-1934) Polish-born French chemist who went to Paris in 1891. She married the physicist Pierre Curie (1859-1906) in 1985 and soon began work on seeking radioactive elements other than uranium in pitchblende (to account for its unexpectedly high radioactivity). By 1898 she had discovered radium and polonium although it took her years to purify them. In 1903 the Curies shared the Nobel Prize for physics with Henri Becquerel, who had discovered radioactivity.
Radon was discovered by Friedrich Ernst Dorn (Germany) in 1900. The origin of the name is variation of the name of element radium; radon was called niton at first, from the Latin word nitens meaning shining. It is colourless, odourless radioactive, heavy, noble gas. Chemically inert and non-flammable. Highly radiotoxic. Carcinogen by inhalation. Radon is formed from the decay of radium in the earths crust. Used to treat some forms of cancer.
Every object in the universe attracts every other object with a force (gravitational force FG) directed along the line through centres of the two objects that is proportional to the product of their masses and inversely proportional to the square of the distance between them.
m1 and m2 are masses of the two objects and r is the distance between them. G is universal constant of gravitation, which equals 6.67•10-26 N m2 kg-2. Strictly speaking, this law applies only to objects that can be considered pointlike object. Otherwise, the force has to be found by integrating the forces between various mass elements.
It is more properly to express Newton’s gravitational law by vector equation:
in which r1 and r2 are position vectors of masses m1 and m2.
Gravitational forces act on distance. Newton’s gravitational law is derived from Kepler’s law for planetary motion, using a physical assumption considering Sun as the centre and the source of gravitational force.
Additionally, every object moves in the direction of the force acting on it, with acceleration that is inversely proportional to the mass of object. For bodies on the surface of Earth, the distance r in gravitational law formula is practically equal to the Earth radius, RE. If the mass of the body on Earth surface is m and the mass of earth is ME, the gravitational force acting on that body can be expressed as:
where g is gravitational acceleration which is, although dependent on geographical latitude, usually considered as constant equal to 9.81 m s-2.
The Lennard-Jones potential (or 12-6 potential) is a mathematically simple model that describes the interaction between two non-bonded and uncharged atoms (known as the van der Waals interaction). It was first proposed in 1924 by British physicist Sir John Edward Lennard-Jones (1894-1954). The Lennard-Jones Potential is given by the following equation
V(r) = 4e[(sigma/r)12-(sigma/r)6)]where V is the intermolecular potential between the two atoms or molecules, ε is the well depth and a measure of how strongly the two particles attract each other, σ is the distance at which the intermolecular potential between the two particles is zero, r is the distance of separation between centres of both particles.
Generalic, Eni. "Van der Waals%E2%80%99s radius." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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