Chemistry

• In 1892 , the german chemist. Johann Wolfgang Dobereiner classified the elements with similar properties into groups called triads
• In 1864 , an industrial chemist, John Newlands arranged the elements in increasing atomic weight
• In 1869 , Russian chemist, Dmitri mendeleev published hir arrangement of the know elements in vertical columns also in order of increasing atomic weights
• Newlans had a musical training so he compared this periodic repetition of properties to octaves and called a the law of octaves
• The german chemist, Julius lothar meyer prepared a periodic table that closely resembles the table of Mendeleev, but he presented his result graphically
• In 1913 , Henry mosely , a young british physicist determined the atomic number of the elements. Mosely findings led to the modification of the periodic table by order of increasing atomic number
• In september 1997 , the international union of pure and applied chemistry (IUPAC) resovled the debate on six laboratory made elements
• Glenn Seaborg was the first living scientist to have an element named after him. He was also the only person who recieved malt addressed only in elements;
• The most commonly used form of periodic table now is called the long form
• The vertical columns of the modern periodical table are referred to as groups or families
• The horizontal rows of periodical table are referred to as periods
• Group 1A to 8A are the representative elements
• Group 1A elements except H are called alkali metals
• Group 2A are referred to as alkaline earth metals
• Group 7A elements are called haloges which means 'salt formers'
• Group 9A are called the noble or rare or inert gases
• Group 3A is sometimes called the boron group
• Group 4A the carbon group
• Group 5A called the nitrogen group
• Group 6 called the oxygen group or chalcogens
• Elements can be classified into four different categories according to their electron configuration:

  • Noble gas
  • Representative elements
  • Inner transition metals
  • Transition metals
• The noble gases are elements that belong to group 8A. Elements in this group are sometimes called inert gases because they do not readily participate in many chemical reaction.
• The representation elements are usally called the Group A elements, They are the elements whose outermost s or p sublevels are only partially field
• The transition metals are called the group B elements,They are the elements whose outermost s sublevels are filled and electrons are added to the d orbitals
• The inner transition metals are sometimes known as transition elements. They are the elements whose electrons are being added to f orbitals