2. The Atom! Unit 4, Chapter 4 Click to see more pictures of the atom

3. And the U UU UNIT Essential Question is… What is the structure of the atom?

4. A. A. Democritus 1. 1. Greek Philosopher 2. 2. First predicted the existence of the atom and gave the atom its name 3. 3. “Atom” means “indivisible” 4. 4. Stated that different atoms have different properties 5. 5. He was laughed at and his theory was not accepted 460-370 B.C. I. I. The development of the atomic model Essential question: How was the atomic model developed? Click on picture for more info

5. B. John Dalton 1. 1. English Chemist 2. 2. Through experimentation in 1803 he developed the first official ATOMIC THEORY 3. 3. His theory was accepted by the world and reads as follows… Essential question: How was the atomic model developed? 1766-1844 Click on picture for more info

6. John Daltons’ 1803 Atomic Theory a. a. Elements are composed of indivisible atoms carbon-oxygen- b. b. Atoms of the same element have the same mass and atoms of different elements have different masses c. c. Compounds contain atoms of more than one element carbon dioxide- d. d. Atoms of different elements always combine in the same way carbon dioxide- carbon dioxide- C O CC C O C OO C OO C OO

7. C. C. J. J. Thomson 1. 1. Discovered negative subatomic particles in 1897 and named them electrons 2. 2. Stated that the atom is a ball of positive material in which electrons are scattered Essential question: How was the atomic model developed? Listen to JJ Thomson Click on picture for more info 1856-1940 Real plum pudding Known as the plum pudding model See video

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9. D. D. Ernest Rutherford 1. 1. Performed his famous gold foil experiment in 1909 2. 2. Discovered that the atom has a dense positive nucleus Click on picture for more info 1871-1937 Essential question: How was the atomic model developed?

10. E. E. Niels Bohr 1. 1. In 1913 predicted that electrons move in fixed energy levels (orbits) around the nucleus Click on picture for more info 1885-1962 Essential question: How was the atomic model developed?

11. 2. 2. Electrons can change orbits as they absorb or release energy Essential question: How was the atomic model developed?

12. Here is how it works… lowest energy higher energy highest energy energy Energy passes through the atomAn electron absorbs some of that energy and moves to a higher energy level Immediately, the electron will return to the ground state releasing that absorbed energy as light This atom is in the ground state repeat

13. Here is how it works… lowest energy higher energy highest energy energy Energy passes through the atomAn electron absorbs some of that energy and moves to a higher energy level Immediately, the electron will return to the ground state releasing that absorbed energy as light This atom is in the ground state repeatcontinue

14. Here is how it works… lowest energy higher energy highest energy energy Energy passes through the atomAn electron absorbs some of that energy and moves to a higher energy level Immediately, the electron will return to the ground state releasing that absorbed energy as light This atom is in the ground state continue

15. F. F. Erwin Schrödinger 1. 1. Predicted the electron cloud model in 1926 2. 2. Energy levels are 3D areas not orbits Essential question: How was the atomic model developed? a. a. Based on complicated math b. b. Shows electrons in an electron cloud (area of probability) Click on picture for more info 1887-1961

16. II. II. The Structure of the Atom Essential question: What are the parts of the atom? 1. 1. Are located in the nucleus of the atom A. A. Protons (p + ) 2. 2. Have a charge of +1 3. 3. Have a mass of one atomic mass unit (AMU) 4. 4. Identify the element Images from education.jlab.org A proton is believed to be made of 3 quarks Bonus info:

17. Essential question: What are the parts of the atom? 1. 1. Are located in the electron cloud B. B. Electrons (e - ) 2. 2. Have a charge of -1 Images from education.jlab.org 3. 3. Have a mass of 1 1836 AMU 0.0005 amu

18. Essential question: What are the parts of the atom? 1. 1. Are located in the nucleus of the atom C. C. Neutrons (n) 2. 2. Have no charge Images from education.jlab.org 3. 3. Have a mass of one AMU A neutron is believed to be made of 3 quarks Bonus info:

19. Here are some more facts about subatomic particles: Essential question: What are the parts of the atom? Bonus Info

20. III. III. Gathering Information on an Element Essential question: What are the number of subatomic particles in a given element? Cl 17 35.453 Chlorine atomic number atomic mass atomic number- the number of protons in the nucleus atomic mass- average mass of the element as it occurs in nature (includes all isotopes) A. A. Using the periodic table

21. mass number- the sum of the protons and neutrons in a given atom Here are a few things to think about: Where is most of the mass found inside the atom? The nucleus Remember that an electron is 1836 times smaller than a proton The mass of the electrons in an atom is insignificant. The largest natural element is uranium which has 92 electrons. The total mass of 92 electrons is still only 5% of the mass of one proton. The mass of the electrons is miniscule compared to the mass of the nucleus The mass of an atom is basically equal to the mass of the nucleus which contains the protons and neutrons The mass of an atom is called the mass number Essential question: What are the number of subatomic particles in a given element?

22. B. B. Processing the information Cl 17 35.453 Chlorine Protons: The number of protons in an element is equal to the atomic number Chlorine has 17 protons neutral atom Electrons: The number of electrons in a neutral atom is equal to the number of protons Chlorine has 17 electrons Neutrons: The number of neutrons in an atom is equal to the mass number minus the atomic number 35 – 17 = 18 Chlorine has 18 neutrons Essential question: What are the number of subatomic particles in a given element?

23. Lets practice! Os 76 190.23 Osmium Protons: The number of protons in an element is equal to the atomic number Osmium has 76 protons neutral atom Electrons: The number of electrons in a neutral atom is equal to the number of protons Osmium has 76 electrons Neutrons: The number of neutrons in an atom is equal to the mass number minus atomic number 190 – 76 = 114Osmium has 114 neutrons Essential question: What are the number of subatomic particles in a given element?

24. 91 – 40 = 51 Zr 40 91.224 Zirconium 40 Protons: Electrons: Neutrons: Essential question: What are the number of subatomic particles in a given element?

25. IV. IV. Isotopes of Atoms Essential question: What are the different forms an atom can take? A. A. All atoms of the same element have the same number of protons B. B. The number of protons never change, they give the atom its identity C. C. Isotopes are atoms of the same element that have a different number of neutrons

26. The Isotopes of Hydrogen H 1 1 H 1 2 H 1 3 protium deuteriumtritium p+ = e- = n = mass = p+ = e- = n = mass = p+ = e- = n = mass = 1 1 0 1 amu 11 11 12 2 amu3 amu H 1 1.0079 This is how hydrogen looks on the periodic table: Which isotope is the most common hydrogen atom in the universe? protium Why? The atomic mass is closest to the mass of protium Essential question: What are the different forms an atom can take?

27. Here is why… What is the average of the following numbers? 333344333344 + 20 6 = 3.3 Are there more 3’s or 4’s in the problem? 3’s Is the average closer to 3 or 4? 3

28. Lets practice!

29. V. V. Ions of Atoms Essential question: What are the different forms an atom can take? A. A. An ion is formed when electrons are lost or gained by an atom B. B. An ion can be negative or positive A negative ion has gained electrons A positive ion has lost electrons oxygen atom, Ooxygen ion, O -2 calcium atom, Cacalcium ion, Ca +2 p+ = 8 e- = 8 p+ = 8 e- = 10 p+ = 20 e- = 20 p+ = 20 e- = 18 No net charge (neutral) -2 chargeNo net charge (neutral) +2 charge