Atoms and Molecules

For today's Science lesson, we went through the concepts on atoms and molecules which we had learnt last year. Then, we went deeper into the topic and gained many new concepts.

3 Thoughts:
1) Atoms contain electrons which they move around the nucleus in regions called electron shells. The more the electrons, the more electron shells an atom has. In addition, only a certain number of electrons move in each of the electron shells. For example, the first shell which is nearest to the nucleus can only hold a maximum of 2 electrons. While the second and third electron shells can each holds a maximum of 8 electrons.
2) The arrangement of the electrons, also known as electronic configuration or electronic structure, is very important as it determines the chemical properties of the atom and we are able to know what changes the element will go through.
3) We had also learnt how to draw electronic structures by using cross or dot to represent each electron. The cross or dot must always be placed opposite each other, like East to West or North to South.

2 Questions:
1) Do all the electrons in the electron shells move in the same way (e.g. clockwise direction)?
2) Why is it only that the inner most of the electron shells can only hold 2 electrons?

1 Useful application:
1) By knowing the arrangement of the electrons in an atom, we are able to know the way how elements are placed in the periodic table.

(Example of an electronic structure of an atom)



Sources: Google Images