1. Atomic Structure Unit 3

2. What is an Atom?  https://youtu.be/hhbqIJZ8wCM https://youtu.be/hhbqIJZ8wCM

3. What is an Atom? The simplest particle of an element that retains its properties.

4. Who is Democritus? This Greek philosopher was among the first to suggest the existence of atoms

5. What did Democritus think?  He believed that atoms were indivisible and indestructible  He thought that atoms looked like a billiard ball

7. What is Dalton’s Atomic Theory? 1)Elements are composed of tiny indivisible particles called atoms 1)Atoms of same element are identical John Dalton (1766 – 1844)

8. What is Dalton’s Atomic Theory? John Dalton (1766 – 1844) 3)Atoms of different elements can combine in simple ratios to form compounds 3)In chemical reactions, atoms are combined, separated, or rearranged – but never changed into atoms of another element

9. Who discovered the electron? J. J. Thomson In 1897

10. How did Thomson discover the electron? A cathode ray

11. Some Modern Cathode Ray Tubes  Cathode ray tubes pass electricity through a gas that is contained at a very low pressure.

12. What did J.J. Thomson conclude?  ALL atoms must contain negative particles.  He knew that atoms did not have a net negative charge and so there must be something balancing the negative charge.

13. What does Thomson’s Atomic Model look like? Thomson believed that the electrons were scattered throughout the atom. It was called the “plum pudding” model.

14. What does Thomson’s ‘plum pudding’ Model look like?

15. Who discovered the nucleus? Ernest Rutherford In 1911

16. How did he discover the nucleus? The Gold Foil Experiment

17. What did this experiment prove? There is a dense positive center in the atom!

18. What else did the Rutherford Atomic Model show?  The atom is mostly empty space  Electrons are scattered throughout the atom

19. What does Rutherford’s Atomic Model look like?

20. What is the center of the atom called? The nucleus

21. What is the nucleus made up of? The nucleus is made up of protons and neutrons

22. Was ALL of Dalton’s atomic theory true? No

23. What was changed from Dalton’s theory?  One change to Dalton’s atomic theory is that atoms are divisible into subatomic particles:  Electrons, protons, and neutrons are examples of these particles

24. What are the three Subatomic Particles? ParticleCharge Mass (g) Location Electron (e - ) (e - ) 0.001 0.001 Electron cloud Proton (p + ) +1 1Nucleus Neutron (n o ) (n o )0 1Nucleus

25. What is the Atomic Number? The “atomic number” of an element is ALWAYS the number of protons in the nucleus ***The number of protons can NEVER change!

26. Example Element Atomic # # of protons Carbon66 Phosphorus1515 Gold7979

27. What is the Mass Number? This is the number of protons and neutrons in the nucleus of an atom

28. What is the charge of an atom? All atoms are NEUTRAL # of Protons = # of electrons

29. What is a Complete Symbol? This is the symbol of the element, its mass number and its atomic number.

30. How do you write a complete symbol? X Mass number Atomic number Subscript → Superscript →

31. How is a complete symbol written on the periodic table?

32. Let’s try together n Find each of these: a) Atomic Number b) Mass Number Br 80 35

33. On your own! n Find each of these: a) Atomic Number b) Mass Number

34. How do you calculate P.E.N? A=P=E Atomic Number Protons Electrons

35. How do you calculate P.E.N? M-A=N Mass Number Atomic Number Neutrons

36. Let’s practice together! If an element has an atomic number of 34 and a mass number of 78, what is the: a) number of protons b) number of electrons c) number of neutrons d) complete symbol

37. On your own! If an element has 91 protons and 140 neutrons what is the a) Atomic number b) Mass number c) number of electrons d) complete symbol

38. Symbols n If an element has 78 electrons and 117 neutrons what is the a) Atomic number b) Mass number c) number of protons d) complete symbol

39.  Topic: Bohr Model Essential Questions: What does an atoms structure look like? How are electrons configured in atoms?

40. What is the Bohr Model?  What is the Bohr Model?  This Model shows electrons in orbit (also called energy shells) around the nucleus P + : 1 E - : 1 N 0 :1-1= 0 1p + e nucleus Electron Energy Shell

41. Constructing a Bohr Model LET’S PRACTICE WITH NITROGEN!  How do we make a Bohr Model? 1. Determine # protons & Neutron  draw them in inner circle 2. Determine # Electrons  place in orbits around the nucleus as follows  1 st orbit= 2e- max  2 nd orbit= 8e- max  3 rd orbit= 8e- max

42. Nitrogen-14 Bohr Model P+E-N0P+E-N0 1.Determine # protons & Neutron  draw them in inner circle 2.Determine # Electrons  place in energy levels as follows 1 st energy level= 2e- max 2 nd energy level= 8e- max 3 rd energy level= 8e- max

43. Let’s Talk About Valence Electrons How do valence electrons effect an elements reactivity?  What are Valence Electrons ?  What’s the Octet Rule ?  Electrons in the outer most shell  Determine elements chemical properties  Atoms gain, lose, or share electrons in order to have 8 valence electrons

45. Let’s Try It Together!!

46. Collaborate! Work With A Partner!

47. Exit Ticket. Try on Your Own! Raise your hand Silently with Questions!

48. What is an ISOTOPE? Atoms of the same element can have different numbers of neutrons. Thus, different mass numbers. ***Remember the number of protons can NEVER change.

49. How do you name Isotopes? We put the mass number after the name of the element :  carbon-12  carbon-14  uranium-235 Mass Number here!

50. Example of an Isotope IsotopeProtonsElectronsNeutronsNucleus Hydrogen–1 (protium) (protium)110 Hydrogen-2(deuterium)111 Hydrogen-3(tritium)112

51.  How heavy is an atom of oxygen?  It depends, because there are different kinds of oxygen atoms. (isotopes)

52. What is Average Atomic Mass? The weighted average of the masses of the isotopes of an element.

53. What is the unit used to Measure Atomic Mass?  The unit we use is the Atomic Mass Unit (amu)

54. How do you calculate average atomic mass?  Step 1: Multiply the atomic mass of each isotope by it’s abundance (change to a decimal)  Step 2: Add the results.

55. Let’s practice together IsotopeSymbol % in nature Carbon-12 12 C 98.89% Carbon-13 13 C 1.11% Carbon-14 14 C <0.01% Carbon = 12.011

56. Example: Element X has 2 naturally occurring isotopes. The isotope ( 10 X) has a relative abundance of 19.91%. The isotope ( 11 X) has a relative abundance of 80.08%. Calculate the average atomic mass of this element.