Discuss how the structure of the atom developed over the years. [5 MARKS]
Discuss how the structure of the atom developed over the years. [5 MARKS]
Dalton Model : 1 Mark
Plum-Pudding Model : 1 Mark
Rutherford's Model : 2 Marks
Bohr's model : 1 Mark
The first theory about the structure of atom was given by John Dalton. According to Dalton, atoms were indivisible particles. But, with the discovery of sub-atomic particles, his theory failed.
Next, J. J. Thomson came out with his own plum-pudding model in which he stated that an atom was a positive sphere in which electrons were embedded on the surface.
Rutherford disproved the plum-pudding model by his gold foil experiment, since many alpha rays passed through the gold foil undeflected meaning, that the entire atom wasn't a positively charged sphere. Since most alpha rays passed undeflected, he stated that most of the atom is free space with a concentrated nucleus at the centre. The electrons revolved around the nucleus in orbits.
Finally Bohr improved the Rutherford's model by stating that the electrons revolve only in specific discrete orbits. In these discrete orbits, the electrons revolve around the nucleus without radiating any energy, thus proving the stability of atoms.
Dalton Model : 1 Mark
Plum-Pudding Model : 1 Mark
Rutherford's Model : 2 Marks
Bohr's model : 1 Mark
The first theory about the structure of atom was given by John Dalton. According to Dalton, atoms were indivisible particles. But, with the discovery of sub-atomic particles, his theory failed.
Next, J. J. Thomson came out with his own plum-pudding model in which he stated that an atom was a positive sphere in which electrons were embedded on the surface.
Rutherford disproved the plum-pudding model by his gold foil experiment, since many alpha rays passed through the gold foil undeflected meaning, that the entire atom wasn't a positively charged sphere. Since most alpha rays passed undeflected, he stated that most of the atom is free space with a concentrated nucleus at the centre. The electrons revolved around the nucleus in orbits.
Finally Bohr improved the Rutherford's model by stating that the electrons revolve only in specific discrete orbits. In these discrete orbits, the electrons revolve around the nucleus without radiating any energy, thus proving the stability of atoms.
