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

The right answer is D.

John Dalton is a British chemist and physicist who developed the atomic theory on which modern physical science was based.

The atom is, for chemists, the fundamental constituent of matter. The term comes from elsewhere a Greek word that means "indivisible", although it is known for a long time that this element is not.

The atom may be associated with other atoms, similar or different, to form a molecule (two oxygen atoms to form O2, or two hydrogen atoms with an oxygen atom to form H2O)

Basically he explained the principle of what is a molecule. He was wrong thinking that atoms are indivisible particles.

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

if you need further assistance, let me know: )

~ trueboss72