Development of the model of the atom

Development of the model of the atom

Learning Objectives

At the end of the lesson you will understand the historical progression of atomic models from Dalton to the Bohr model. At the end of the lesson you will be able to describe the key experiments and discoveries that led to the development of the nuclear model of the atom. At the end of the lesson you will be able to compare the relative masses and charges of protons, neutrons, and electrons. At the end of the lesson you will recognize the significance of the alpha scattering experiment in disproving the plum pudding model. At the end of the lesson you will be familiar with the concept of electron shells and their role in the Bohr model.

What do you already know about the structure of the atom?

Dalton's atomic model as indivisible solid spheres

The model of the atom as solid, indivisible spheres. John Dalton's early representation of the atom.

Discovery of sub-atomic particles and the plum pudding model

Discovery of electrons challenged Dalton's model. J.J. Thomson's plum pudding model with electrons in a positively charged matrix.

Alpha scattering experiment and the nuclear model of the atom

Ernest Rutherford's experiment with alpha particles on gold foil. Discovery of the dense nucleus and the nuclear model of the atom.

The concept of the nucleus and discovery of protons and neutrons

The nucleus as the central part of the atom. Identification of protons and neutrons within the nucleus.

Relative mass of protons, neutrons, and electrons

Comparison of the relative masses of protons, neutrons, and electrons. Protons and neutrons are almost 2000 times heavier than electrons.

Bohr's electron shell model and fixed energy levels

Niels Bohr's atomic model with electrons orbiting the nucleus at fixed distances known as shells or energy levels.

Definition List

Atom, Dalton's model, Plum pudding model, Alpha scattering experiment, Nuclear model, Nucleus, Proton, Neutron, Electron, Relative mass, Electron shell (Bohr) model

Write down 3 things you learned in this lesson.

Have students enter three things they learned in this lesson. With this they can indicate their own learning efficiency of this lesson.

Write down 2 things you want to know more about.

Here, students enter two things they would like to know more about. This not only increases involvement, but also gives them more ownership.

Ask 1 question about something you haven't quite understood yet.

The students indicate here (in question form) with which part of the material they still have difficulty. For the teacher, this not only provides insight into the extent to which the students understand/master the material, but also a good starting point for the next lesson.