Question

what new characteristic did john dalton add to the model of the atom?
an atom is a round, solid mass.
an atom has a massive, positive center.
an atom is made up of smaller particles.
an atom can join with other kinds of atoms.

Explanation:

John Dalton proposed that atoms are round, solid masses (the billiard - ball model). He also stated that atoms of different elements combine in simple whole - number ratios to form compounds, which implies that an atom can join with other kinds of atoms. The idea of an atom having a massive, positive center was proposed by Rutherford, and the concept of an atom being made up of smaller particles came later with the discovery of electrons, protons, and neutrons.

Answer:

A. An atom is a round, solid mass.
D. An atom can join with other kinds of atoms.