Structure of Atoms Chapter 3

Study Notes

Atoms are tiny particles that make up everything around us, but they are too small to be seen with the naked eye, even with powerful microscopes.
An atom consists of two main parts: the nucleus at the center and electrons revolving around the nucleus outside.
The nucleus contains positively charged protons and neutral neutrons, while electrons orbiting around the nucleus carry a negative charge.
When an atom has an equal number of protons and electrons, the total charge is zero, and it is called a neutral atom.

The nucleus is made up of protons and neutrons, with the mass of a neutron and proton being approximately 2,000 times more than the mass of electrons.
As a result, the mass of an atom is essentially the mass of its nucleus.

Atoms can gain or lose electrons to enhance their stability, resulting in a charge imbalance and the formation of ions.
Different atoms have different structures due to varying numbers of protons and electrons, leading to different properties in different elements.

The concept of atoms dates back to the 5th century BC, with Leucippus and Democritus proposing that substances are made up of tiny, indivisible particles called atoms.
Democritus coined the term "atom" from the Greek word "atomos," meaning "indivisible."
Aristotle believed in the concept of four elements: fire, earth, air, and water, but didn't provide experimental proof.
In the 18th and 19th centuries, scientists like John Dalton, J.J. Thomson, Ernest Rutherford, and Niels Bohr contributed to the development of the modern atomic model.

John Dalton proposed that atoms are the smallest particles of matter and cannot be divided further (1803).
Rutherford and his colleagues conducted an experiment to determine the exact structure of an atom, concluding that all positive charge and mass are confined to a small nucleus.
Bohr's atomic model also gained significant acceptance.