1. Atoms and Atomic Theory
Overview
Atomic Structure (protons, electrons, neutrons)
Isotopes
Electron shells, energy levels
Periodic table

2. Characteristics of Atoms
Atoms possess mass
Atoms contain positive nuclei
Atoms contain electrons
Atoms occupy volume
Atoms have various properties
Atoms attract one another
Atoms can combine with one another to form molecules

3. Atomic Structure Atom Protons Nucleus: protons (+) and neutrons (0)
Electrons (–)
Protons
All atoms of same element have same number of protons
Number of protons in the nucleus defines the element
Atomic number (A) = nuclear charge

4. Atomic Number
Symbol and atomic number signify same thing.

5. Mass Number Protons and neutrons in the nucleus
Sum of p + n = mass number (Z)
Number of neutrons can vary within a given element
Variations are called isotopes C
12C
6 p
6 n
13C
6 p
7 n
14C
6 p
8 n *
*radioactive (unstable)
11C
6 p
5 n C 12 6

6. Problem 1 Complete the following table of isotopes: Symbol #p #n
Atomic number
Mass number
26Al 37 86 17 18

7. Problem 1 Complete the following table of isotopes: Rb Symbol #p #n
Atomic number
Mass Number
26Al 37 86 17 18 13 13 13 26 86 Rb 37
86 – 37
= 49 = 35
35Cl 17

8. Atomic Weight Weighted average of all naturally occurring isotopes
Mass number = n + p, whole number, particular isotope
Atomic weight, decimal,
combination of all isotopes naturally found
experimental number

9. Atomic Weight 7 N
99.63 % 14N: amu
0.37 % 15N: amu
14.01
0.9963( ) ( ) =
= amu

10. Problem 2
Magnesium has three naturally occurring isotopes with the following masses and abundances:
23.99 amu %
24.99 amu %
25.98 amu %
Calculate the atomic weight of magnesium.

11. Problem 2 + (24.99 amu)(0.1000) + (25.98 amu)(0.1101) = 24.31 amu
amu correlation to grams

12. The “Mole”
Chemists use “moles” as a way to count atoms which are so tiny
Industry analogs
Atomic weight (molar mass) connects gram amount to atomic mass units (which is related to proton/neutron mass)
Avogadro’s number: 6.02 x 1023
Numerically correlated:
24.31amu  24.31g/mol
Know grams  know atoms

13. Periodic Table Electronic structure Bohr Model flawed but functional
Electronic energy levels
How do scientists (chemists) use models?

14. Models Useful to simplify complex or confusing systems
Understand behavior of aspects of universe
Limitations, oversimplification
Atomic models vs. atomic theory

15. Law versus Theory
Discuss each of the following terms (as is typically done in society). Give an example of each.
Law
Theory

16. Scientific Perspective
Law: generalization based upon observation (measurement) to which there are no exceptions
Law of gravity
Gas Laws
Newton’s Laws of Motion
No theoretical framework, empirically based

17. Scientific Perspective
Theory: model that describes underlying cause of physical behavior (law)
Predictive
Goes beyond laws from which formulated
Testable (experiment)
Examples
Kinetic Molecular Theory
Atomic Theory
How do models fit?

18. Atomic Theory
Atomic Theory and Quantum Mechanical model of the atom developed through interaction of matter with light (electromagnetic radiation)

19. Electromagnetic Spectrum

20. Visible Spectrum

21. Bohr Model Line spectra Light through a prism  continuous spectrum:
Ordinary
white
light

22. Bohr Model Line spectra Light from gas-discharge tube
through a prism  line spectrum:
H2 discharge tube

23. Line Spectra (emission)
White light H He Ne

24. Line Spectra (absorption)
Gas-filled tube
Light source

25. Electronic Energy Levels
n = electronic energy level
n = 1 2 electrons (H, He)
n = 2 8 electrons (Li  Ne)
NOT orbits, energy levels
2e–
8e–

26. Electronic Energy Levels
n = main electronic energy level
Sublevels: s, p, d, f
n = 1, s only: 2 electrons maximum
n = 2, s & p: 2 electrons in s, 6 electrons in p
n = 3, s, p & d: 2 electrons in s, 6 electrons in p, 10 electrons in d
n = 4, s, p, d, f: s-2, p-6. d-10, f has 14
Filling order is unexpected

27. Electronic Energy Levels
Filling order 1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f 5g
6s 6p 6d
7s 7p

28. Electronic Energy Levels
n = electronic energy level
Sublevels: s, p, d, f
n = 3 s and p fill first: 8 electrons (Na  Ar)
n = 4
4s fills before 3d (K, Ca)
but 3d fills before 4p (Sc  Zn)
4p (Ga  Kr)
Periodic table can be “derived” from energy levels
2e–
8e–
8e–

29. Periodic Table (p. 293)
n = 1
n = 2
n = 3
n = 4

30. Electronic Energy Levels
Inner shell versus outer shell electrons
Inner shell: not involved in formation of chemical bonds
Outer shell: involved in formation of chemical bonds
Outer shell  valence electrons

31. Valence Electrons 1e- 2e- 3e- 4e- 5e- 6e- 7e- 8e- H He Li Be B C N O FNe Na Mg Al Si P S Cl Ar
n = 1
n = 2
n = 3

32. Problem 3
Draw the electron configurations for each of the following elements according to the Bohr model. Indicate which electrons are valence electrons. S Na C

33. Problem 3
a) S, 16 electrons

34. Problem 3
a) S, 16 electrons

35. Problem 3
b) Na, 11 electrons

36. Problem 3
b) Na, 11 electrons

37. Problem 3
c) C, 6 electrons

38. Problem 3
c) C, 6 electrons

39. Probability Density Functions (Beyond the Bohr Model)
Link to Ron Rinehart’s page
 energy
2 probability density function
s, p, d, f, g 1s 3s 2s
Node: area of 0 electron density

40. Probability Density Functions
Node: area of 0 electron density
nodes
Link to Ron Rinehart’s page

41. Ions and Ionic Compounds
Ion: gained or lost electrons to be a charged species (NEVER PROTONS!)
Cl + e–  Cl–
anion: -chg
17 p+
17 e–
17 p+
18 e–
Na  Na+ + e–
cation: +chg
Na+ with Cl–
NaCl
11 p+
11 e–
11 p+
10 e–

42. Problem 4 Complete the following table of ions: Symbol #p #e Al3+ Br–16 18 12 10

43. Problem 4 Complete the following table of ions: Symbol #p #e Al3+ Br–16 18 12 10 13 10 35 36 2– S 2+ Mg