Experiences

Consistence of atoms

Mária Fabiánová

Slovakia

Lower Secondary School

Chemistry

Teaching in class

Direct

For students to understand the structure of matter I use the concept of matter as everything that surrounds us. Matter is manifested in two forms: as a substance and as a physical field. Substances consist of molecules, molecules consist of atoms, and atom has a nucleus and an electron envelope. In nucleus there are nucleons and in envelope are electrons. This is the basic sequence of terms.
The word “atom” was used for the first time in the 5th century BC in ancient Greece. It was caused by the simple fact: people were curious. Again, I recall that it is needed to understand the way of life then and now. Leucippus and his student Democritus started to deal with this thought. They wanted to know the smallest particle into which a substance can be divided. It can be shown on a piece of long chalk which will be broken into half, quarter …. In Greece they came to the conclusion that the smallest particle is an atom – “atomos” which means undividable. For 2.5 thousands of years no one ever doubted it or it was not possible to technically prove or deny this thought until 1805 when British scientist J.Dalton has proven that atoms really exist.
Even though I teach that a matter is everything, when I ask whether even air is a matter, students’ answer is that it is not because they cannot touch it. In order to show them that they are wrong I tell them that it is sufficient to estimate the dimensions of the class to find out the density of air and we can calculate that there is about 70 kg of air in the classroom. Next I at least mention how the scientists got inside the atom and had discovered its structure. Neutron, particle that is placed in the nucleus and is the heaviest, was not discovered until 1932 which is from scientific point of view very recent past. Also it is interesting to compare the dimensions of the nucleus with the whole atom. Let’s say that my table is 1m long and that it is a dimension of the nucleus then the end of this hypothetical atom would be in Nitra. The distance between my table and Nitra represents electron envelope in which are placed electrons. The mass of electrons is very small so electron envelope weights almost nothing. All these thoughts lead to claiming which is for students very difficult to understand and it is that the atom is actually from the point of its size an empty space and has a small heavy nucleus.
Neither the picture that is usually drew in textbooks and on the blackboard does not reflect the reality but it is not possible to show it other way.
It is difficult to describe development of views on the structure of atoms so I mention at least the first idea – the pudding model – the base is the basic matter and in this matter are scattered negative electrons as raisins in a pie. The size of positive and negative charge is always the same and atom as a whole is electrically neutral.
It is not important to say other facts because it would lead us to the quantum physics and students does not have knowledge of it
This topic require a great deal of abstract thinking, connecting of knowledge and understanding that “something” is created of “nothing”.
I do not know how to evaluate this experience but I suppose that it was partially positive.