Which statements in Dalton's atomic theory are now considered to be incorrect?

Answer 1

Dalton's theory (circa 1800) in part stated:

"Atoms cannot be created, divided into smaller particles, nor destroyed."

"All atoms of an element are identical and that in particular they have the same mass."

Because Dalton studied only chemical reactions, there are basically 3 inaccuracies in these statements:

1) We now know that atoms are divisible and are composed of smaller, subatomic particles (electrons, protons, and neutrons). Some of these, in turn, are formed from more energetic particles called quarks. Atoms are also subdivided by nuclear decay and fission into other atoms.

2) Atoms of an element are not necessarily identical in mass - elements have isotopes (atoms with this same proton number but different numbers of neutrons) which means that atoms of an element do not have to have the same mass.

3) Atoms cannot be destroyed in chemical reactions, but parts of their mass may be converted to energy in nuclear reactions, which were unknown until the late 19th century. Theoretically, atoms could be created from energy in a reverse reaction.

Answer 2

1) One problem with his atomic theory was that it claimed that all matter is composed of tiny indivisible atoms. We now know that atoms are divisible and are composed of smaller, subatomic particles (electrons, protons, and neutrons).

2) He also stated that atoms of an element are identical in mass- this is incorrect because all elements have isotopes (atoms with this same proton number but different numbers of neutrons) which means that atoms of an element do not have to have the same mass.

Answer 3

One of them is Nothing can be smaller then an atom