Thomson used a beam of negatively charged particles. Using a beam of particles and detecting the scattering of the particles after they hit gold foil.
Stoichiometry measures these quantitative relationships, and is used to determine the amount of products/reactants that are produced/needed in a given reaction.
Malleability described the property of physical deformation under some compressive stress; a malleable material could, for example, be hammered into thin sheets. Malleability is generally a property of metallic elements: The atoms of elemental metals in the solid state are held together by a sea of indistinguishable, delocalized electrons. This also partially accounts for the generally high electrical and thermal conductivity of metals.
In any case, only one of the elements listed here is a metal, and that’s copper. Moreover, the other elements (hydrogen, neon, and nitrogen) are gases under standard conditions, and so their malleability wouldn’t even be a sensible consideration.
