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# The Atom

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1. The Atom

2. Essential Question? Compare and contrast the characteristics of an atom and function of these characteristics in an atom?

3. Structure of an Atom

4. Protonp+ • Positive Charge (p+) • Located in the nucleus • Mass of a proton = 1.673 x 10-24g • Relative Mass 1 amu • Function: Gives an atom its identity – If the # of protons changes so does the type of atom Ex: Hydrogen has 1 proton Helium has 2 protons Lithium has 3 protons • The Atomic # always equals the # of protons Ex: Hydrogen has an Atomic # = 1 and has 1 proton Proton

5. Neutronno Neutron • No charge • Located in the nucleus • Mass of a neutron 1.675 x 10-24g • Relative Mass = 1 amu • Function: Adds mass to nucleus • Mass # - Atomic # = # of no Ex: 1-1=0 hydrogen has 0 no

6. Electrone- Electron • Negative charge • Has very small mass (9.109 x 10-28g) and is not included in the atomic mass of the atom • Relative Mass = 1/1840 • Located outside the nucleus - electron cloud - orbitals - shells - energy levels Ex: Hydrogen has 1e- • Function: Is responsible for an atoms behavior

7. Atomic # = # protons = # electrons • Which element has 32 protons? Symbol__ Name __ • Which element has 14 protons? Symbol__ Name __ • The mass number is the number of protons PLUS the number of neutrons in an atom. • This is because the mass of the atom is mainly inside the nucleus where the protons and neutrons are found. • The mass number – protons = number of neutrons on the Periodic Table

8. Find and Round the Atomic Mass to the nearest whole number

9. Find and Round the Atomic Mass to the nearest whole number

10. Three types of atoms

11. This will help you determine which type of atom you have • If the p+≠ e- then you have an ION • If you add the p+ + no & the mass # ≠ the mass on the PT, you have an ISOTOPE • If the mass # = the mass # on the PT, and the p+ = e- then you have an Element

12. Element • Cannot be broken down into simpler substances by physical or chemical means • Each has a symbol located on the Periodic Table Ex: Ag – Silver, Pb – Lead • Each has an atomic # and atomic mass Ex: Ag – Atomic # = 47 Atomic mass = 107.9 amu Pb – Atomic # = 82 Atomic mass = 207.2 amu • Atomic # = # of p+ = # of e- • If the # of p+ = the # of e- the atom is electrically neutral • Atomic mass = # of p+ + # of no (this number must match the rounded atomic mass (or Mass #) on the periodic table)

13. Element - Fill in the table below

14. ElementFill in the table below

15. Ion • An ion is an atom with a charge. The charge is either positive or negative • The charge depends on if the electrons are donated (lost) or accepted (gained) Ex: If an atom donates e- then the charge becomes positive (+) Na+ Ex: If an atom accepts e- then the charge becomes negative (-) Cl- • To identify an ion the # of protons will NOT equal the # of electrons Ex: Cl normally has 17e- A Cl- ion has 18e- (Cl has accepted 1e-)

16. Ion - Fill in the table below

17. Ion - Fill in the table below Are the number of protons and electrons the same or different? DIFFERENT

18. Isotopes • Are atoms with the same number of protons but has a different number of neutrons than the normal number of neutrons in an atom • To calculate the # of no round the atomic mass to the nearest whole number then subtract the atomic number. • When the atomic mass is rounded it is called the Mass number Mass number–Atomic number =# of no Ex: (Pb) 207 – 82 = 125 neutrons • If the atom is an isotope then there will be more neutrons and the mass will be more Ex: (Pb) 208 –82 = 126 neutrons • Isotopes are neutron rich and unstable

19. Isotopic Notation Ex: Silicon Mass # 28 Si 14 Atomic # Isotopic Name Silicon-28 Mass #

20. Let’s Compare the Following

21. Let’s Compare the Following How are the notations alike? How are the above notations different? Same protons and electrons Different Mass # & neutrons

22. Review Isotopes are atoms of the same element with the same number of _______, but with different numbers of _______. Answer questions 1-5 in Part I Answer questions 6-10 in Part II

23. Complete Isotopes or Different Elements WSFront and back

24. Complete Isotopes or Different Elements WSFront and back

25. Fill in the Chart Below

26. Fill in the Chart Below

27. Summarize • Fill in Part V chart

28. Fill in the Chart Below

29. Fill in the Chart Below

30. Fill in the Chart Below

31. Fill in the Chart Below

32. Summarize • Answer questions part VI

33. Part VII Potassium • K – 39 has 20 neutrons • K – 40 has 21 neutrons • K – 41 has 22 neutrons

34. Atomic Mass Determination • Chemist have developed a method of measuring mass of an atom called: Atomic Mass Determination Unit is abbreviated “amu” • They did this because the masses of subatomic particles are so small that even scientific notation makes it hard to calculate the masses of elements. • The atomic mass that you see on the PT is the average mass for the isotopes of that element. • The atomic mass you see on the PT is also the isotope that is most abundant in nature!!! • Answer Question 1 & 2

35. How is Atomic Mass Calculated? • The mass on the Periodic Table is the average mass of the isotopes of an atom • To determine the atomic mass of an atom use this formula (Mass (amu) x Percent abundance)= Isotope A (Mass (amu) x Percent abundance)= Isotope B Add A + B / 100 = atomic mass

36. Example Problem #1 • Calculate the atomic mass of the unknown element. Then identify the element using the Periodic Table?

37. (184.953 amu x 37.40) = 6917.35 amu (186.956 amu x 62.60) = 11703.45 amu 6917.35 amu trace/least abundant +11703.45 amu most abundant 18620.8 / 100 = 186.2 amu Rhenium = Re

38. Practice Problem #2 • Calculate the atomic mass of the unknown element. Then identify the element? Which Isotope is trace and which is more abundant?

39. (112.904 amu x 4.30 ) = 485 amu (114.904 amu x 95.70) = 10996.3128 amu 485 amu trace/least abundant +10996.3128 amu most abundant 11481.3128 / 100 = 114.81 amu Indium = In

40. Practice Problems (Book) • Pp. 104 15-17 #15Boron has 2 naturally occurring isotopes: boron-10(abundance = 19.8%, mass = 10.013 amu), boron-11 (abundance = 80.2 %, mass = 11.009 amu) Calculate the atomic mass of boron. #16 Helium has 2 naturally occurring isotopes, helium-3 and helium-4. The atomic mass of helium is 4.003 amu. Which isotope is more abundant in nature? Explain #17 Calculate the atomic mass of magnesium. The three magnesium isotopes have atomic masses and relative abundances of 23.995 amu (78.99%), 24.986 amu (10.00%), 25.982 amu (11.01%).

41. Practice Problem #1 Answer = 10.81 amu 5 5

42. Practice Problem #2 Answer = 107.9 amu 47 47

43. Practice Problem #3 Answer = 24.31 amu 12 12 12

44. Practice Problem #4 Helium-4 is most abundant b/c its mass is closer to the average atomic mass on the PT Helium-3 mass is not as close as Helium-4, so Helium-3 is less abundant

45. Practice Problem #5 Answer = 20.19 amu 10 10

46. Practice Problem #6 Answer = 178.55 amu 72 72 72 72 72

47. Practice Problem #7 Answer = 28.09 amu 14 14 14

48. Practice Problem #8 Answer = 107.87 amu 47 47

49. Practice Problem #9 Answer = Neon-20 Why? Its mass is closest to the average mass of neon on the PT.

50. Practice Problem #10 Answer = 83.80 amu 36 36 36 36 36 36