1. Virtually everything that is, is made up of atoms. Chapter 12, page 361 Balloon and sweeter animation

2. Sub-Particles in the Atom Each element is chemically unique. To understand why they are unique, you need to know the structure of the atom (the smallest particle of an element) and the characteristics of its components. Element = made of one kind of Atom. Li Compounds = made of different atoms chemically bonded in whole number ratios. H 2 O Mixtures are physical combinations of elements or compounds with variable composition O 2 + H 2. Particles or Pure substances

3. Sub-Particle Mass Charge Location in the Atom proton~1 a.m.u. 1+ in nucleus neutron~1 a.m.u. 0 in nucleus electron~0 a.m.u. 1- orbits nucleus Sub-Particles in the Atom atomic.mass.unit= a.m.u. ~ 1.992 ×10 −27 kg or 1/12 the mass of C-12kg

4. Structure of the Atom There are two regions The nucleus With protons and neutrons – Positive charge – Almost all the mass Electron cloud – Most of the volume of an atom – The region where the electron can be found

5. Size of an atom Atoms are incredibly tiny. Measured in picometers (10 -12 meters) – Hydrogen atom, 32 pm radius Nucleus tiny compared to atom – Radius of the nucleus near 10 -15 m. – Density near 10 14 g/cm 3 IF the atom was the size of a stadium, the nucleus would be the size of a marble. California WEB

6. Balloon and sweeter animation Balloon and sweeter animation What holds an atom together? Nuclear Tug-Of-War Electrostatic force – like charges repel and un-like charges attract Strong Nuclear Force – holds nucleons (p+ & n0) together, very strong nuclear force but over short distances – Stable nuclei are SMALL – Large nuclei tend to be unstable (radioactive) Electrostatic Force – Holds electrons on atom

7. Counting Particles in Atoms Atomic Number = number of protons (p+) = unique for each element Atomic Mass Number = Mass of an atom = number of protons + neutrons = (p+) + (no); (e- do not have mass) California WEB 12 6 C 14 6 C 12 6 C Mass Number = A Atomic Number = Z

8. How can I remember how many protons or electrons there are? Just remember the A.P.E. rules! atomic number = number of protons= number of electrons

9. Now, how do I remember how many protons there are? Just remember the M.A.N.! mass number - Atomic number= number of neutrons

10. Neon Ne Protons: Electrons: Neutrons: Atomic Number: 10 Atomic Mass: 20 10

11. Phosphorus P Protons:15 Electrons: Neutrons: 16 Atomic Number: Atomic Mass: 15 31

12. Aluminum Al Protons: Electrons: 13 Neutrons: 14 Atomic Number: Atomic Mass: 13 27

13. Argon Ar Protons:18 Electrons: Neutrons: Atomic Number: Atomic Mass: 40 18 22

14. Silicon Si Protons: Electrons: Neutrons: 14 Atomic Number: 14 Atomic Mass: 14 28

15. Symbols Contain the symbol of the element, the mass number and the atomic number (top heavy) X Mass number Atomic number # protons + # neutrons mass number

16. Symbols Find the – Atomic number – Mass number – number of electrons – number of protons – number of neutrons F 19 9 = 9 = 10 = 9 = 19 +

17. So let’s practice!

18. Symbols Find the –number of protons –number of neutrons –number of electrons –Atomic number –Mass number Br 80 35 = 35 = 45 = 35 = 80 http://www.chem.purdue.edu/gchelp/liquids/bromine.gif

19. Symbols Find the – number of protons – number of neutrons – number of electrons – Atomic number – Mass number Na 23 11 Sodium atom = 11 = 12 = 11 = 23

20. To find net charge on an atom, consider the p + and the e –. cation: a (+) ion -- more p + than e – -- formed when atoms lose e – anion: a (–) ion -- more e – than p + atoms -- formed when gain e – ion: a charged atom - - + + + - - + + + - - e-e- p+p+ n0 n0 - + + + - +3 and -4 = -1 - - e-e- p+p+ n0 n0 - + + + - +3 and -2 = +1 Ions

21. Symbols Find the – number of protons – number of neutrons – number of electrons – Atomic number – Mass number Na 23 11 1+ Sodium ion = 11 = 12 = 10 = 11 = 23

22. Symbols If an element has an atomic number of 23 and a mass number of 51 what is the –number of protons –number of neutrons –number of electrons –Complete symbol V 51 23 = 23 = 28 = 23

23. Symbols If an element has 60 protons and 84 neutrons what is the –Atomic number –Mass number –number of electrons –Complete symbol Nd 144 60 = 60 = 144 = 60

24. Symbols If a neutral atom of an element has 78 electrons and 117 neutrons what is the –Atomic number –Mass number –number of protons –Complete symbol Pt 195 78 = 78 = 195 = 78

25. Masses of Atoms  Mass Number  Isotopes  Ions  Relative Atomic Mass  Average Atomic Mass Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

26. Mass Number mass number= protons + neutrons always a whole number NOT on the Periodic Table! + + + + + + Nucleus Electrons Nucleus Neutron Proton Carbon-12 Neutrons 6 Protons 6 Electrons6 e-

27. Isotopes Atoms of the same element with different mass numbers. Mass # Atomic # Nuclear symbol: carbon-12Hyphen notation: carbon-12 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem 12 6 C

28. Isotopes Dalton was wrong. Atoms of the same element can have different numbers of neutrons. different mass numbers. called isotopes.

29. Isotopes + + + + + + Nucleus Electrons Nucleus Neutron Proton Carbon-12 Neutrons 6 Protons 6 Electrons6 Nucleus Electrons Carbon-14 Neutrons 8 Protons 6 Electrons6 + + + + + + Nucleus Neutron Proton

30. What is an isotope? same number of protons, different numbers of neutrons. Boron-10BProtons:Electrons:Neutrons: Atomic Number: 5 Atomic Mass:10 Boron-11BProtons:Electrons:Neutrons: Atomic Number: 5 Atomic Mass:11 5 5 5 5 5 6 B-10 10 B 5 B-11 11 B 5

31. Carbon- C Protons: Electrons: Neutrons: 6 Atomic Number: 6 Atomic Mass: What is the average atomic mass of Carbon? Carbon- C Protons: 6 Electrons: Neutrons: Atomic Number: Atomic Mass:14 6 6 12 6 8 6 14

32. Isotopes Chlorine-37 – atomic #: – mass #: – # of protons: – # of electrons: – # of neutrons: 17 37 17 20 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Cl 17 37 17 Cl

33. Writing Isotopes Put the mass number after the name of the element carbon- 12 carbon -14 uranium-235 – Or California WEB 12 6 C Mass # Atomic # 12 6 C

34. Using a periodic table and what you know about atomic number, mass, isotopes, and electrons, fill in the chart: ElementSymbolAtomic Number Mass # # of protons # of neutron # of electron charge 888 Potassium 39+1 Br45 306530 Atomic Number = Number of Protons Number of Protons + Number of Neutrons = Atomic Mass Atom (no charge) : Protons = Electrons Ion (cation) : Protons > ElectronsIon (anion) : Electrons > Protons

35. Using a periodic table and what you know about atomic number, mass, isotopes, and electrons, fill in the chart: ElementSymbolAtomic Number Mass # # of protons # of neutron # of electron charge 888 Potassium 39+1 Br45 306530 Oxygen Bromine Zinc O K Zn 8 19 35 16 80 19 35 30 20 35 18 36 0 0 Atomic Number = Number of Protons Number of Protons + Number of Neutrons = Atomic Mass Atom (no charge) : Protons = Electrons Ion (cation) : Protons > ElectronsIon (anion) : Electrons > Protons A N S W E R K E Y

36. Isotopes Because of the existence of isotopes, the mass of a collection of atoms has an average value. Average mass = ATOMIC WEIGHT = ATOMIC MASS Boron is 20% B-10 and 80% B-11. – That is, B-11 is 80 percent abundant on earth. For boron atomic mass = 0.20 (10 amu) + 0.80 (11 amu) = 10.8 amu

37. Average Atomic Mass massed average of all isotopes on the Periodic Table round to 2 decimal places Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Avg. Atomic Mass = (mass)(%) + (mass)(%) 100

38. Average Atomic Mass EX: Calculate the avg. atomic mass of oxygen if its abundance in nature is 99.76% O-16, 0.04% O-17, and 0.20% O-18. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Avg. Atomic Mass = (16)(99.76) + (17)(0.04) + (18)(0.20) 100 = 16.00 amu

39. Average Atomic Mass EX: Find chlorine’s average atomic mass if approximately 8 of every 10 atoms are chlorine-35 and 2 are chlorine-37. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Avg. Atomic Mass = (35)(8) + (37)(2) 10 = 35.40 amu

40. Assume you have only two atoms of chlorine. One atom has a mass of 35 amu (Cl-35) The other atom has a mass of 36 amu (Cl-36) What is the average mass of these two isotopes? 35.5 amu Looking at the average atomic mass printed on the periodic table...approximately what percentage is Cl-35 and Cl-36? 55% Cl-35 and 45% Cl-36 is a good approximation Cl 35.453 17