Atoms

1. Atoms

2. With what the universe is made out of ?

5. What is an Atom ? • Atoms are the tiny particles that everything is made out of . • It is the basic unit of matter. • An Atom is made out of subatomic particles called Electrons, Protons and Neutrons. • The name atom comes from the Greek name “Atomos” which means uncuttable .

6. Ancient Geeks believed that atom is what you get when you cut something and bring it to the state that you cannot cut it any further. That is why they called it Atomos meaning uncuttable. • They believed that the atom could not be divided further.

7. Greek Philosopher Democritus

8. Democritus BIO DATA SCIENTIFIC FINDINGS Full name;- Democritus School/tradition;- Pre- Socratic philosophy Main interests;-metaphysics, mathematics, astronomy Notable ideas;- Atonism, Distant Star Theory He was the 1st to say that everything in the world (matter) can be divided into small structures. He named this basic structure as an atom. He defined it as “Atoms are invisible structures that consist of a mass”

9. How subatomic particles are arranged in the atom ? • Neutrons and protons are densely packed in the nucleus. • Electrons are moving around the nucleus at different electrical energy levels or shells. • Scientists now believe that protons and neutrons are made out of even smaller particles called “Quarks” and “Leptons”.

10. The mass number means the number of protons and neutrons in the nucleus in an atom of an certain element. • Atomic number is the number of protons in an atom of an certain element. Number protons is equal to the number of electrons before the atom make any bonds or subject to any change.

11. Atomic structure • Atomic structure means the way the subatomic particles (electrons, protons, neutrons) of the atom are arranged inside the atom. • Many different scientists have put forward many concepts about the atomic structure. Eg : Billiard Ball Model – John Dalton Plum Pudding Model – J.J. Thomson Cubical Atom Model – Gilbert Lewis Planetary motion – Ernest Rutherford Bohr- Sommerfeld model – Neil Bohr Modern atomic structure – Debrogley, Hinesburg and Shrewdinger. • Some of them are detailed below

12. Plum Pudding Model • This structure was put forward by J.J. Thomson in 1904. • In this atomic structure J.J. Thomson has told that as shown in the picture in the right, that negatively charged “plums” are on the positively charged “pudding”. • But this model was later disapproved.

13. Planetary Model • This model is put forward by Ernest Rutherford in 1911. • He said that positively charged particles are concentrated at the middle in a small area and the electrons are circling around it as the planets rotate around the sun.

14. Bohr- Sommerfeld Model • This model is put forward by the scientist Neil Bohr. • His concept was that the protons and the neutrons are concentrated in the middle and the electrons are moving around the nucleus in elliptical paths.

15. Modern Atomic structure • This atomic structure was put forward by Debrogley, Hinesburg and Shrewdinger. This is the atomic structure that is even believed today. • Their concept was that while the protons and neutrons are concentrated at the center, the electrons move around the nucleus at different energy levels or shells. • 1st energy level (K) – 2 electrons 2nd energy level (L) – 8 electrons 3rd energy level (M) – 18 electrons 4th energy level (N) – 32 electrons 5th energy level - 12 electrons

16. Group Members Malika Narada Dineth Rushil Himasha Kalana Shamika Ashan Arthif Visal

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