Dalton and Thomson
Part of the Atomic Structure section of Coddy's Chemistry journey. Lesson 6 of 45.
In 1803 John Dalton said every element is made of its own kind of atom, and pictured an atom as a tiny solid ball that cannot be split.
In 1897 J. J. Thomson found the electron: a tiny particle with a negative charge, found in every atom. Atoms have parts after all.
A whole atom has no charge, so positive charge must balance the electrons. Thomson's plum pudding model: a ball of positive charge with electrons dotted through it.
Dalton's solid ball (1803) and Thomson's plum pudding (1904)
Challenge
Thomson's rule: an atom has no overall charge, so its negative electrons balance its positive charge. A carbon atom holds 6 units of positive charge, called protons. Build a carbon atom with no overall charge.
Try it yourself
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Atomic Structure
1Matter and Atoms
What Everything Is Made OfElements, Compounds, MixturesChemical SymbolsCounting Atoms in a FormulaRecap - Molecule Kit2Models of the Atom
Dalton and ThomsonRutherford's Gold FoilThe Nuclear AtomBohr's ShellsRecap - From Ball to Nucleus