1. Ch. 19 - Atomic Structure I. Structure of the Atom I. Chemical Symbols  Subatomic Particles

2. A. Chemical Symbols  Capitals matter!  Element symbols contain ONE capital letter followed by lowercase letter(s) if necessary. Co vs. CO Metal that forms bright blue solid compounds. Poisonous gas.

3. B. Subatomic Particles Most of the atom’s mass. Atomic Number equals the # of... in a neutral atom NUCLEUS ELECTRONS PROTONS NEUTRONS NEGATIVE CHARGE POSITIVE CHARGE NEUTRAL CHARGE ATOM

4. C. Subatomic Particles  Quarks 6 types 3 quarks = 1 proton or 1 neutron The sixth is called the top quark He video

5. D. Models  Models are a way for scientists to simplify concepts and ideas when studying things like atoms.  Early models of the atom used a solid sphere. Early models  The current atomic model is an accumulation of over 200 years of knowledge! The current electron cloud model has electrons traveling in specific energy levels around the nucleus.

6. Electron Cloud Model  Region where there is a high probability of finding an electron.  Can’t pinpoint the location of an electron.  Density of dots represents degree of probability.

7. Ch. 19 - Atomic Structure Section II. Masses of Atoms

8. A. Atomic Mass  atomic mass unit (amu)  1 amu = 1 / 12 the mass of a 12 C atom  1 proton = 1 amu 1 neutron = 1 amu  Sum of the protons and neutrons in the nucleus of an atom. © Addison-Wesley Publishing Company, Inc.

9. Atomic number  Always a whole number.  The number of protons in an atom. # protons identifies the element!!  # of neutrons = mass # - atomic #

10. B. Isotopes  Atoms of the same element with different numbers of neutrons. Mass # Atomic #  Isotope symbol: “Carbon-12”

11. C. Isotopes  Different isotopes have different properties. © Addison-Wesley Publishing Company, Inc. How do you calculate neutrons?

12. C. Isotopes  Average Atomic Mass reported on Periodic Table weighted average of all isotopes It is closest to its most abundant isotope. Avg. Atomic Mass

13. Avg. Atomic Mass C. Isotopes  EX: About 8 out of 10 chlorine atoms are chlorine-35. Two out of 10 are chlorine-37. 35.4 amu

14. Ch. 19 Section 3 - The Periodic Table

15. Organization of the Periodic Table  Currently organized by atomic number.  Dmitri Mendeleev (1869, Russian chemist) Organized elements by increasing atomic mass. Discovered a pattern – properties that repeated = periodic Predicted the existence of undiscovered elements.

16. Dmitri Mendeleev’s Predictions

17. Predicted Properties of Ekasilicon (Es) Actual Properties of Germanium (Ge) Existence predicted: 1871 Actual discovery: 1886 Atomic Mass: 7272.61 High melting ptMP = 938 C Density = 5.5 g/cm3 D = 5.323 g/cm3 Dark gray metalGray metal

18. Henry Mosely  Henry Mosely (1913, British) Organized elements by increasing atomic number. Fixed problems in Mendeleev’s arrangement.

19. Problems with Mendeleev’s model Mass decreases!

20. Groups  Vertical columns are called groups and have similar properties. Group 11 Copper Silver Gold Shiny, metals that are good conductors

21. Periods  The horizontal rows of the elements that contain increasing numbers of protons and electrons. Increase by one proton and electron left to right.

22. Regions on the Periodic Table  Metals  Nonmetals  Metalloids

23. Electron Cloud Structure  Electrons within the cloud have different amounts of energy  Modeled by placing electrons in “energy levels”.  Elements in the same group have the same number of electrons in their outer energy level.  This determines properties of the element

24. Electron Cloud Structure  Each energy level can have a maximum number of electrons. Level 1 – 2 Level 2 – 8  Filled from inside out.  Energy levels nearer the nucleus have lower energy than those farther away.

25. Electron Cloud Structure  Carbon?  Oxygen?  Sodium?

27. Electron Cloud Structure  Valence Electrons: Number of electrons in the outermost energy level.  Determines properties of each element

28.  A stable (complete) outer energy level contains eight electrons (usually).  Each row ends when an outer energy level is filled. (i.e. He and Ne)

29. Rows on the Table  Each row begins filling a new energy level. (row 1 = 1st, row 2 = 2nd etc) Li? Na? K?

30. Electron Dot Diagrams  Use element symbol and dots to represent outer (valence) electrons.

31. Electron Dot Diagrams  Each row begins filling a new energy level. (row 1 = 1st, row 2 = 2nd etc) Li? Na? K?

32. Same group = similar properties including ability to form compounds Group 1 and Group 17 K and I? Will group 18 form compounds?

33. Same group = similar properties including ability to form compounds Group 1 and Group 17 K and I? Will group 18 form compounds?

34. Dot Diagram Practice Which group will Group 2 elements react with?