Atoms:
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history and development of atoms.
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Atoms:
- 2. Matter is anything that takes up space and has mass All matter is made of atoms the building blocks of matter, sort of how bricks are the building blocks of houses. Smallest particles of matter
- 3. • An atom has three parts: • Proton = positive • Neutron = no charge • Electron = negative • The proton & neutron are found in the center of the atom, a place called the nucleus. • The electrons orbit the nucleus.
- 4. HISTORY OF THE ATOM 460 BC Democritus develops the idea of atoms he pounded up materials in his pestle and mortar until he had reduced them to smaller and smaller particles which he called ATOMA (greek for indivisible)
- 5. Democritus’ Atom Indivisible particle
- 6. HISTORY OF THE ATOM 1808 John Dalton suggested that all matter was made up of tiny spheres that were able to bounce around with perfect elasticity and called them ATOMS
- 7. Dalton’s Atom Postulated the Atomic Theory
- 8. HISTORY OF THE ATOM 1904 Thompson develops the idea that an atom was made up of electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electron's charge like plums surrounded by pudding. PLUM PUDDING MODEL Electrons embedded in positive mass
- 9. HISTORY OF THE ATOM 1910 Ernest Rutherford He suggested that the positive charge was all in a central nucleus. With this holding the electrons in place by electrical attraction Positive nucleus
- 10. HISTORY OF THE ATOM 1913 Niels Bohr studied under Rutherford at the Victoria University in Manchester Bohr refined Rutherford's idea by adding that the electrons were in orbits. Rather like planets orbiting the sun. With each orbit only able to contain a set number of electrons.
- 11. Bohr’s Atom electrons in orbits nucleus
- 12. Bohr’s Atom Electron Nucleus Fixed electron orbit
- 19. Isotopes Atoms that have the same number of protons but different numbers of neutrons Example:
- 20. is the difference between the mass of nucleons (protons and neutrons) and the mass of the nucleus Atomic number the number of protons in an atom the number of protons and neutrons in an atom Mass defect He2 4 Atomic mass number of electrons = number of protons
- 21. HELIUM ATOM N + + N - - proton Shell electron neutron What do these particles consist of?
- 22. Particle proton neutron electron Charge + ve charge No charge -ve charge Particle Electrical Charge Mass 1 1 0.000549 Mass (amu) Proton +1 1.0072766 or 1 Neutron 0 1.0086654 or 1 Electron -1 0.000549
- 23. Total Mass of Nucleus = 1.00794 Total Mass of Nucleus = 4.00260 Total Mass of Nucleus = 12.011
- 24. Ground State – lowest energy level of an electron Excited State – the electron goes into a higher energy level An electron emits energy as it returns to its ground state
- 25. When an electron absorbs energy in the form of light or heat, it goes into a higher energy level. The electron is said to be in the excited state. When an excited electron returns to its ground state, it emits the energy it previously absorbed .
- 26. SPECTRUM If light is passed through a prism, an array of colors called SPECTRUM is formed.