1. Chemistry I Chapter 3 Introduction to Atoms

2. How small is an atom?

3. Atoms

4. Atoms vs. Hyle
Atom - the smallest particle of an element. It can exist alone, or combined with other atoms.
Atoms were first suggested by Democritus (Greek philosopher, 400B.C.).
People that supported Democritus view were called “Atomists”.
Aristotle(300B.C.) did not support the idea of atoms. He believed that all matter was a continuous substance called hyle. Hyle was composed of: earth, air, fire and water.

5. Democritus vs. Aristotle

6. John Dalton….THE MAN!
John Dalton-(English school teacher) first to explain the existence of atoms and disspelling Aristotle’s theory of matter.

7. John Dalton Formulates Atomic Theory:
Each element is made up of tiny indivisible particles called atoms.
The atoms of a given element are identical, atoms of different elements are different.
Chemical compounds are formed when atoms come together, in simple whole number ratios.
Chemical reactions involve the reorganization of the atoms; combined, separated or rearranged.

8. 1903: J.J. THOMSON
Discovers the electron, using his famous Cathode Ray Tube (CRT), which turns out to be a primitive TV or computer monitor.

9. Discovery of the Electron
In 1897, J.J. Thomson used a cathode ray tube to deduce the presence of a negatively charged particle, the electron.
Cathode ray tubes pass electricity through a gas that is contained at a very low pressure.

10. CRT and TV

11. 1911 Ernest Rutherford
Rutherford discovers the nucleus of an atom, using his famous gold foil experiment.

12. Rutherford’s Gold Foil Experiment

13. Rutherford’s Gold Foil Experiment

14. Rutherford’s Gold Foil Experiment
Alpha () particles are helium nuclei
Particles were fired at a thin sheet of gold foil
Particle hits on the detecting screen (film) are recorded

15. Rutherford’s Gold Foil Experiment

16. How big is an atom?

17. Characteristics of sub-atomic particles
Particle symbol charge location mass
Proton p nucleus 1 amu
Neutron no 0 nucleus 1 amu
Electron e orbital /1840 amu
amu = atomic mass unit, unit used to mass very
small objects. (1 amu = 1/12 the mass of a
carbon-12 nucleus)
Orbital – the 3-dimensional space around the nucleus of an atom, where electrons are found most of the time.

18. Atomic Structure

19. Atomic Models
JJ Thomson model(Plum pudding model) electrons are scattered throughout the atom, like raisins in plum pudding.
Rutherford Model-The atom has a central dense core, but is mostly empty space.
Bohr Model(Planetary model)Electrons orbit the nucleus in circular paths, called energy levels
Quantum Model (Modern, Shrodinger model)- Electrons move randomly in spaces called orbitals, around the nucleus.

20. Thomson’s Atomic Model
Thomson believed that the electrons were like plums embedded in a positively charged “pudding,” thus it was called the “plum pudding” model.

21. Rutherford’s Findings
Most of the particles passed right through
A few particles were deflected
VERY FEW were greatly deflected
“Like howitzer shells bouncing off of tissue paper!”
Conclusions:
The nucleus is small
The nucleus is dense
The nucleus is positively charged

22. The Bohr Model of the Atom
I pictured electrons orbiting the nucleus much like planets orbiting the sun.
But I was wrong! They’re more like bees around a hive.
Neils Bohr

23. Quantum Mechanical Model of the Atom
Mathematical laws can identify the regions outside of the nucleus where electrons are most likely to be found.

24. Important definitions about atoms:
atomic number = number of protons in the nucleus of an atom. The number of protons determines the element of an atom.
atomic mass number = mass of the atom in amu, it includes the number of protons and neutrons.
(electrons are not counted)
Isotopes = atoms of the same element, with a different number of neutrons in the nucleus. Isotopes of each element have the same atomic number, but different mass numbers.

25. TAKS QUESTION

26. Isotopes

27. Boron isotopes

29. Find the number of protons, neutrons and electrons in each:
Carbon-14
Nitrogen-15
U-235
Hydrogen-3
Carbon-13
Helium-3
B-11
Cu-64

30. Periodic Table Families

31. List the Element Family:
Element Family Element Family Br Fe K U Sr Si Ce C Ar Cs

32. Orbital- the 3-d space around the nucleus of an atom where an electron is found most of the time. Each orbital can hold up to 2 electrons of opposite spin.

33. Orbitals have different shapes:
Orbital shape
s spherical
p dumbbell
d clover or
dumbbell/donut
f too complex

34. Energy sublevels around an atom
energy electron
sublevels # of orbitals capacity s p d f g*
*orbitals exist, but not used most of the time.

35. Aufbau Order- Energy levels & orbital types around the atom
Aufbau order- Electrons fill orbitals closest to the nucleus first.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p,6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p

36. Orbital notation

37. Electron configuration

38. Valence Electrons/Lewis Dot Notation

39. How to calculate average atomic mass

40. Pre AP Chemistry: Nuclear Equations
Nuclear Reactions(transmutation reactions) are represented with Nuclear Equations.
Transmutation reactions – a reaction where one nucleus changes element.
(# of protons)

41. Nuclear equations
See board

42. Half-life: the amount of time it takes for ½ of a sample to react or decay.
The half life of Ti-48 is 47 hrs. How much of a 250 gram sample remains after 94 hrs?
A 100gram sample of Cd-114 decays until only 12.5 grams remain in a total of 41years. What is the half-life for this isotope?

43. TAKS QUESTION

44. Electron orbitals
Orbital – a 3-dimensional space around the nucleus which can hold up to 2 electrons, with opposite spin.
*electrons are found in their orbitals 99.9% of the time.
Orbitals have different shapes: s, p, d, f

45. Orbitals have different shapes:
Orbital shape
s spherical
p dumbbell
d clover or
dumbbell/donut
f too complex

46. s-orbitals: spheres

47. p-orbitals: dumbbell

48. d-orbitals: clover (double dumbbell) or dumbbell/donut

49. f-orbitals: complex

50. Energy sublevels around an atom
energy electron
sublevels # of orbitals capacity s p d f g*
*orbitals exist, but not used most of the time.

51. Orbital Notation Aufbau Order:
(Nucleus)1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f
**This is the order in which electrons fill!!!!!
You must learn the order!! Don’t worry there is always an easier way to memorize these things. For the Aufbau Order there are 2 ways: With arrows or with the periodic table! Smartboard activate!

52. Electron Configurations and the Periodic Table
Figure 8.7

53. Orbital Notation Write the orbital notation for each atom:
Nitrogen, N(7 electrons)
Sodium, Na(11 e-)
Iron, Fe(__ e-)
Antimony, Sb(__ e-)
Gold, Au(__ e-)