Video Transcript
Who first postulated the
solid-sphere model of the atom?
The first atomic theory was
proposed in 400 BCE by the ancient Greek philosophers Leucippus and Democritus. They proposed that the universe is
composed of indivisible particles called atoms that have different sizes, shapes,
and even textures. They reasoned that iron atoms were
strong with hooks that locked them into a solid, water atoms were smooth and
slippery, and salt atoms were sharp and pointy. Due to a number of critics of this
model and the lack of sophisticated scientific equipment, atomic theory didn’t
develop further for many hundreds of years.
In 1803, a meteorologist named John
Dalton published a landmark paper proposing a new atomic theory. His model had four basic
assumptions. Dalton proposed that the chemical
elements were made up of indivisible particles called atoms. Atoms of one chemical element are
unique and different from the atoms of another chemical element. He also proposed that atoms cannot
be created nor destroyed during a chemical reaction and that atoms of one element
cannot change into atoms of another element. The fourth assumption is that
compounds are formed when atoms combine and that product compounds should have the
same number and type of atoms as the reactants. John Dalton’s theory and postulates
are collectively known as the solid-sphere model.
So the scientist who first
postulated the solid-sphere model of the atom is Dalton.
