Notes of Lessons: Physical Science, Class IV

[We have thought that it might be of use to our readers (in their own families) to publish from month to month during the current year, Notes of Lessons prepared by students of the House of Education for the pupils of the Practising School. We should like to say, however, that such a Lesson is never given as a tour de force, but is always an illustration or an expansion of some part of the children’s regular studies (in the Parents’ Review School), some passage in one or other of their school books.—Ed.]

Subject: Atoms • Group: Science • Class IV • Time: 45 minutes

By Laura M. MacDonald
The Parents’ Review, 1909, pp. 631-632

Objects

I. To give the girls an idea of the construction of atoms.

II. To show how elements may be classified.

Lesson

Step I.—Summary of Last Lesson.

(1) Atoms are made up of electrons.

(2) How this fact was discovered.

(3) What we know about electrons. Their nature and size.

Step II.—Reading by the girls from “Scientific Ideas of To-day,” pp. 52-56.

(1) Analogies to illustrate manner in which the atom is composed. Each atom is a miniature solar system, in which the electrons move in regular orbits, one ring within another, at so great a velocity that the atom appears to consist of solid lifeless matter.

(2) Facts about electrons. Electrons are units of negative electricity, therefore they should repel each other, and the atom would be dissipated, if there were nothing to keep the balance. (Illustration, by means of bar magnets, showing how like repels like, and opposite attracts opposite.)

It follows that there must be an equal quantity of positive electricity in anatom to maintain an equilibrium. Nothing, however, is known about it, beyond the fact that it is present.

It is probable that there is a uniform sphere of positive electricity in the atom, throughout which the electrons are distributed. The positive electricity attracts the electrons to the centre of the sphere, while the electrons repel one another. Thus an equilibrium is produced.

Step III.—Experiment with floating magnets to enable the pupils to form a mental picture of the atom.

Step IV.—Reading by the girls from “Scientific Ideas of To-day,” pp. 58-59.

Electrons have a stable or equilibrium arrangement, therefore many different atoms have a certain similarity. For instance, one atom has one electron in the centre and six others round it, while another has exactly the same arrangement with an additional ring of eleven electrons outside it. It follows that substances composed of similar atoms have similar properties.

Step V.—Illustrate this fact by finding points of similarity between two substances, potassium and sodium, which are composed of similar atoms.

(1) Both are soft metals, are easily cut.

(2) Both have a silver-like lustre, when cut, which soon tarnishes.

(3) Both ignite on a damp surface.

Step VI.—Reading pp. 59-60.

(1) All elements can be arranged in groups according to the structure of their atoms, on which depends the atomic weight of the elements.

(2) Newlands Octaves. If substances bearranged according to their atomic weight, beginning with the highest and going down to the lowest, those elements belonging to the same family occur at regular intervals in the scale.

Step VII.—Summary of Lesson.

Headings for Blackboard.

(1) Construction of Atom.

(2) Different kinds of atoms.

(3) Family groups of elements.

(4) Newland’s Octaves.