1. CHAPTER 4 Atomic Structure

2. Atoms An atom is the smallest particle of an element that retains its identity in a chemical reaction.

3. History Democritus (460-370BC): first suggested the existence of the atom

4. History John Dalton (1766-1844): proposed the Atomic Theory:  1. All elements are made of atoms  2. Atoms of the same element are identical  3. Atoms of different elements can combine to form compounds  4. Chemical reactions occur when atoms are separated, joined, or rearranged

5. Size of the atom One penny contains 2.4x10 22 atoms of copper 100,000,000 atoms in a row would be 1 cm long Atoms can be seen with special microscopes called scanning tunneling microscopes

6. Atomic Structure An atom can be broken down into subatomic particles: protons, neutrons, and electrons.

7. Parts of an atom The nucleus is the tiny central core of an atom containing protons and neutrons Surrounding the nucleus is the electron field where electrons are located. If an atom was the size of a football field, the nucleus would be the size of a marble located on the 50 yard line.

8. Subatomic Particles ParticleSymbolLocationChargeMass (g) Electrone-e- orbital-9.11 x 10 -28 Protonp+p+ nucleus+1.67 x 10 -24 Neutronn0n0 nucleus01.67 x 10 -24

9. Protons Protons are positively charged subatomic particles located in the nucleus

10. Neutrons Neutrons are subatomic particles with no charge, equal in size to protons, and found in the nucleus.

11. Electrons Electrons are negatively charged subatomic particles, which are very small, and orbit the nucleus.

12. Important Scientists J.J. Thomson (1897) discovered electrons using a cathode ray tube. Cathode Ray Experiment

13. Important Scientists Ernest Rutherford (1911) discovered protons through his gold foil experiment. Gold Foil Experiment Animation

14. Reading and Writing in Science 1. Read pages 100-108 in the red textbook 2. Answer questions 1-14 on pages 103 and 108. Write and answer these questions in your notebooks. Next notebook collection date is October 30.

15. Distinguishing Among Atoms Atoms of an element are different because they contain different numbers of protons. The atomic number of an element is the number of protons an atom of that element has.

16. Practice How many protons does each element have? Hydrogen Carbon Nitrogen Potassium Gold

17. Practice How many protons does each element have? Hydrogen = 1 Carbon = 6 Nitrogen = 7 Potassium = 19 Gold = 79

18. Mass Number The other number on the periodic table is an atom’s mass number which is the sum of protons and neutrons. What is the mass number of: Hydrogen Carbon Nitrogen Potassium Gold

19. Mass Number The other number on the periodic table is an atom’s mass number which is the sum of protons and neutrons. What is the mass number of: Hydrogen (1.0079) Carbon (12.011) Nitrogen (14.007) Potassium (39.098) Gold (196.97)

20. Neutrons To determine the number of neutrons an atom has, you subtract the atomic number from the mass number, then round to the nearest whole number. How many neutrons are found in: Hydrogen Carbon Nitrogen Potassium Gold

21. Neutrons To determine the number of neutrons an atom has, you subtract the atomic number from the mass number, then round to the nearest whole number. How many neutrons are found in: Hydrogen = 0 Carbon = 6 Nitrogen = 7 Potassium = 20 Gold = 118

22. Electrons In a neutral atom, the number of electrons is equal to the number of protons, which is equal to the atomic number. How many electrons does each atom have? Hydrogen Carbon Nitrogen Potassium Gold

23. Electrons In a neutral atom, the number of electrons is equal to the number of protons, which is equal to the atomic number. How many electrons does each atom have? Hydrogen = 1 Carbon = 6 Nitrogen = 7 Potassium = 19 Gold =79

24. Determining subatomic particles ParticleNumber ProtonsAtomic Number ElectronsAtomic Number NeutronsAtomic mass – atomic number

25. Isotopes Isotopes are atoms that have the same number of protons but different numbers of neutrons (and therefore different mass numbers).

26. Isotopes The most well known isotope is Carbon-14. Regular Carbon is called Carbon-12, because its mass number is 12, and it has 6 neutrons. Carbon 14 has 8 neutrons (14-6). It is used for radioactive dating of fossils.

27. Getting to know the Periodic Table You should memorize the names and symbols of common elements on the periodic table. Complete the activity to help you get to know the elements of the periodic table.

28. Determining Subatomic Particle Numbers In your lab notebooks, create a chart of the first 90 elements (1  90), including the following information: Round neutrons to the nearest whole number! Honor’s Only: Answer questions 1-14 on pages 103 and 108. This is extra credit for Regular Chemistry. NameSymbolAtomic Number Atomic Mass (amu) ProtonsElectronsNeutrons HydrogenH11.008110

29. History of Atomic Models Over time, scientists proposed different models of atoms, each better than the last. Rutherford said that positive protons were in the nucleus, and electrons orbited it.

30. Atomic Models Bohr stated that the nucleus had positive protons, and electrons orbited in fixed shells.

31. Atomic Models Schrodinger proposed the quantum mechanical model, which is still used today. It states that there are protons and neutrons in the nucleus, which is surrounded by an electron cloud showing the probability of electron location.

32. Electrons Electrons are found outside the nucleus in shells/orbitals/energy levels.

33. Energy Levels The number of electrons allowed in each energy level is: Energy Level (n)Maximum Number of Electrons 12 28 318 432

34. Placing electrons Each energy level must be full before electrons can be placed in the next level up. Example: Draw an atom of Lithium

35. Lithium

36. Practice Draw an atom of Sodium.

37. Sodium

38. Practice In your notebooks, draw the first 30 atoms. Name each one, and place the correct numbers of protons, neutrons, and electrons in each. This is what your quiz will be like (Tuesday for periods 5 and 7, Wednesday for period 2)