as understanding increased
- This is a diagram of an atom with seven electrons, as described J. J. Thomson in a lecture in 1905. In that lecture, he presented a diagram (File:Thomson_atom_electron_arrangements.jpg) in which he showed hypothetical arrangements of electrons in an atom. This image is based on Thomson’s rendition of a seven-electron atom. The electrons are arranged in a pentagonal dipyramid. At the time, Thomson believed that even small atoms contained thousands of electrons, but calculating how so many electrons would arrange themselves in an atom was too computationally difficult for him. In 1913, scientists deduced that an atom contains a number of electrons equal to its atomic number. This atom with seven electrons would therefore be nitrogen, but by then the plum pudding model had been declared obsolete.
- Mariana Plate (Wikipedia)
The Mariana Plate is a micro tectonic plate located west of the Mariana Trench which forms the basement of the Mariana Islands which form part of the Izu–Bonin–Mariana Arc. It is separated from the Philippine Sea Plate to the west by a divergent boundary with numerous transform fault offsets. The boundary between the Mariana and the Pacific Plate to the east is a subduction zone with the Pacific Plate subducting beneath the Mariana. This eastern subduction is divided into the Mariana Trench, which forms the southeastern boundary, and the Izu–Ogasawara Trench the northeastern boundary. The subduction plate motion is responsible for the shape of the Mariana plate and back arc.
