Which event would be impossible to explain by using john dalton’s model of the atom?

An iron atom emits particles when it is struck by light (by the photoelectric effect)

Explanation:

The first atomic model was the one proposed by Jhon Dalton, according to which it is postulated that:

"Matter is made up of indivisible, indestructible and extremely small particles called atoms."

That is, the atom is a solid and indivisible mass.

However, the fenomenom by which an iron atom emits particles when it is struck by light (known as the photoelectric effect) can not be explaind by this indivisible atom model.

To understand it better:

The photoelectric effect consists of the emission of electrons (electric current) that occurs when light falls on a metal surface under certain conditions.

This is possible by considering light as a stream of photons, where each of them has energy. This energy is be able to pull an electron out of the crystalline lattice of the metal and communicate, in addition, a kinetic energy.  This means the atom is not indivisible, but it is a composition of different particles.

In fact, currently it is known that each atom is composed of a nucleus and one or more electrons attached to the nucleus, which is composed of one or more protons and typically a similar number of neutrons.