Answer :
Answer:
The correct order is shown by the first option:
(1) the atom is a hard sphere → most of the atom is empty space → electrons exist in orbitals outside the nucleus
Explanation:
1) the atom is a hard sphere
This was the original conception of the atom.
The plum pudding model, developed by the scientist, J.J. Thompson, by 1904, after the discovery of the electron, represented the atom as a solid positively charged sphere with electrons embeded and uniformly distributed in it.
2) most of the atom is empty space
It corresponds to the model developed by Rutherford, by 1911.
The famous experiment of α-particles bombarding a thin foil of gold, yield to the discovery of the atomic nucleous and the proposition that the mass of the atom is mostly concentrated in a dense small positevely charged nucleous with electrons (negative charged) around of it and a lot of empty space in between the electrons and the nucleous. This model did not explain how the electrons were arranged.
3) electrons exist in orbitals outside the nucleus.
Few years later, by 1913, the scientist Niels Bhor, proposed the model in which the electrons were in fixed orbits around the nucleous, just like the planets orbit around the sun, to explain the emission spectra of the atoms.
This was not the last theory. It was not exact and a new atom quantum model was soon developed, but this is not part of the question.
The atomic models were given by various scientists. At first, the atom was considered a hard-sphere then an empty space later with the discovery of electrons they were placed in the orbitals. Thus, option A is correct.
What is the atomic model?
An atomic model is the representation of the atom with the charges and the sub-atomic particles based on various experiments. At first, the atom was considered just a hard sphere. This was established by Thompson's plum pudding model.
Later the atom was considered an empty space and was established by Rutherford's scattering experiment. It includes the bombardment of the α-particles on a gold foil.
Later it was discovered that electrons being negative surrounds the nucleus of the atom in their fixed orbitals or the sub-shells. It was proposed by Bohr's atomic model.
Therefore, option A. hard sphere > empty space > and electrons in fixed orbitals are the order of their atomic models.
Learn more about atomic models here:
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