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Structure of Atoms

Electron cloud. Nucleus consisting of protons and neutrons. Structure of Atoms. Electron cloud. Nucleus consisting of protons and neutrons. Electron: It carries a negative charge. It has a mass only about 1/1850 of the proton. It is orbiting the nucleus at high speeds.

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Structure of Atoms

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  1. Electron cloud Nucleus consisting of protons and neutrons Structure of Atoms

  2. Electron cloud Nucleus consisting of protons and neutrons Electron: It carries a negative charge. It has a mass only about 1/1850 of the proton. It is orbiting the nucleus at high speeds. Proton: It is found in the nucleus . It carries a positive charge.

  3. Electron cloud Nucleus consisting of protons and neutrons Neutron: It does not carry any charge. It has about the same mass as a proton.

  4. Atoms of different elements have different number of protons, electrons and neutrons. Example:

  5. The atomic number is the number of protons in an atom.

  6. Mass number: It is the total number of protons and neutrons in the nucleus of an atom.

  7. For any neutral atom, the number of electrons is equal to the number of protons.

  8. Data for atoms of the first 20 elements

  9. Quiz Electron cloud Nucleus consisting of protons and neutrons Draw a labelled diagram to show the structure of an atom.

  10. Quiz What is the charge of electron? Electron: It carries a negative charge. What is the charge of proton? It carries a positive charge. Compare the mass of electron and that of proton. Electron has a mass only about 1/1850 of the proton. Describe the movement of electron in an atom. It is orbiting the nucleus at high speeds.

  11. Quiz What is the charge of a neutron? Neutron: It does not carry any charge. Compare the mass of neutron and that of proton. They have about the same mass. How do you know atomic number of an atom from the number of protons? The atomic number is the number of protons in an atom.

  12. Exercise 1. Complete the following table.

  13. Exercise Suggested Answers

  14. Exercise 2. Complete the following table for three element A, B and C

  15. Exercise Suggested Answers

  16. Exercise 3. Complete the following table.

  17. Exercise Suggested answers

  18. Electronic Configuration 4th shell (energy level) 3rd shell nucleus 2nd shell 1st shell (energy level) It is the distribution of electrons in the various shells of an atom.

  19. Electronic Configuration Energy of the electron in the first shell is lower nucleus

  20. Electronic Configuration Energy of the electron in the third shell is higher nucleus

  21. Electronic Configuration The first shell can hold a maximum of 2 electrons

  22. Electronic Configuration The second shell can hold a maximum of 8 electrons

  23. Electronic Configuration The third shell can hold a maximum of 18 electrons

  24. The following rules can be applied to find out the electronic configuration of an atom. The first 2 electrons go into the first shell and complete it. The next 8 electrons go into the second shell and complete it. The next 8 electrons go into the third shell. The next 2 electrons go into the fourth shell. The next 10 electrons go into the third shell and complete it.

  25. Try exercises given on p.18!

  26. Electron Diagram

  27. Electron Diagram For example, hydrogen atom E.C.: 1 Electron diagrams also show the distribution of electrons in atoms.

  28. Electron Diagram Lithium atom, atomic no. = 3 E.C. : 2, 1

  29. Electron Diagram Sodium atom, atomic no. = 11 E.C. : 2, 8, 1

  30. Electron Diagram Calcium atom, atomic no. = 20 E.C. : 2, 8, 8, 2

  31. Work out electronic configuration and electron diagram for beryllium, atomic no.=4 Beryllium atom E.C. : 2, 2

  32. Work out electronic configuration and electron diagram for fluorine atom, atomic no.=9 E.C. : 2, 7

  33. Work out electronic configuration and electron diagram for aluminium, atomic no.=13 E.C.: 2, 8, 3

  34. Potassium atom, atomic no. = 19 E.C.: 2, 8, 8, 1

  35. mass number atomic number Full atomic symbols

  36. Full atomic symbols mass number atomic number

  37. In general mass number atomic number

  38. Try the exercise (p.19)!!

  39. 1 2 3 H H H 1 1 1 3.5 Isotopes Isotopes are atoms of a particular element with the same number of protons and electrons but a different number of neutrons. Three isotopes of hydrogen.

  40. 37 Cl 35 Cl 17 17 3.5 Isotopes Isotopes of an elements have the same number of electrons, therefore the same electronic configuration. They have different mass numbers. Two isotopes of chlorine

  41. Which of the following are isotopes of the same element? Explain. A, C are isotopes of an element. B, D are isotopes of another element. Atoms A and atom C have the same number of protons but of different number of neutrons.

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