Minit molecular model kit, 1981.
© Science Museum / Science & Society Picture Library
This student pocket set for organic and inorganic chemistry, complete with booklet, was made by Cochranes of Oxford Ltd. The kit enables models of molecular structure to be constructed by connecting 'atoms' to each other by connecting rods representing bonds. The number of bonds an atom can form is determined by an element's valency, which is dictated by the number of electrons in the outermost shell of an atom of that element.