Structure of the atom notes-CBC Grade 9 Notes in Kenya
Structure of the atom notes
Atoms are the smallest particle of a chemical element that can possibly exist. We have learnt that atoms and molecules are the basic building blocks of matter and the existence of different kinds of matter is due to different atoms which constitute them. Through CBC Grade 9 science notes for Structure of atoms we understand the structure and composition of atoms in detail.
Atoms are very small particles of an element, but they contain even smaller particles called sub- atomic particles as follows;
- Protons – found in the nucleus, they are positively charged (+ve)
- Electrons – found in the nucleus, they are negatively charged (– ve)
- Neutrons – they can be imagined as circulating the nucleus in energy levels, they have no charge
In a neutral atom, Number of protons = Number of electrons
The various energy levels in an atom are represented by a series of circles sharing the same centre (nucleus), separated from each other by roughly equal distances.
The nucleus of the atom is at the centre of the circles. The electrons in the energy levels are represented by dots (.) or crosses (x). The energy levels are labelled 1st, 2nd, 3rd, 4th and so on starting from the one nearest to the nucleus as shown below;
The electrons that occupy the 1st energy level have lower energy than those in the 2nd energy level. Subsequently those in the 2nd energy level have lower energy than those in the 3rd energy level and so on. The 1st energy level usually has a maximum of two electrons while the 2nd energy level has a maximum of eight (8) electrons.
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