ATOMIC STRUCTURE

1. ATOMIC STRUCTURE

2. HISTORY OF THE ATOM Democritus develops the idea of atoms 460 BC He pounded up materials in his pestle and mortar until he had reduced them to smaller and smaller particles which he called ATOMOS (greek for indivisible)

3. HISTORY OF THE ATOM

4. 16 X + 8 Y 8 X2Y Law of Conservation of Mass 2.1

5. HISTORY OF THE ATOM electrons

6. HISTORY OF THE ATOM FYI ONLY….If the atom is the Ralph Wilson Stadium Then the nucleus is a marble on the 50 yard line (1909 Nobel Prize in Chemistry)

7. http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swfhttp://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf Results: 99% of the alpha particles went straight thru, 1% were deflected. Be able to explain and summarize Rutherford’s Gold Foil Experiment 2.2

8. HISTORY OF THE ATOM

9. Bohr’s Atom- electrons move in definite, fixed orbits around the nucleus electrons in orbits nucleus

10. HISTORY OF THE ATOM

11. HISTORY OF THE ATOM reviewed • Atomos song http://www.youtube.com/watch?v=WK7wuTwAiBU Crash Course https://www.youtube.com/watch?v=thnDxFdkzZs Science Classroom https://www.youtube.com/watch?v=IO9WS_HNmyg

12. Atoms • The basic unit of Matter • The smallest particle of an element that retains the properties of that element. • Made up of subatomic particles

13. ATOMIC STRUCTURE All About Atoms Particle Charge Mass Proton + charge 1amu Neutron No charge 1 amu electron - charge 1/1836

14. ATOMIC STRUCTURE He 2 Atomic number Represents the number of protons in an atom Never changes P+ equal to the number of e- 4 Mass Number the number of protons and neutrons in an atom Neutrons equal mass # - atomic # number of electrons = number of protons

15. HELIUM ATOM Shell proton N + - + N - neutron electron What do these particles consist of?

16. Isotopes • Atoms with the same atomic number but different mass number or • Atoms having the same number of protons but different numbers of neutrons • Which atom is an isotope of oxygen? 1). O 2). O 3). O • Isotopic notation: O or O-16 17 16 16 6 7 8 16

17. 2.3

18. 2. How many protons, neutrons, and electrons are in ? ? 3. How many protons, neutrons, and electrons are in 11 14 C C 6 6 CHEM DO…Do You Understand Isotopes? 1. Define an isotope 6 protons, 8 (14 - 6) neutrons, 6 electrons 6 protons, 5 (11 - 6) neutrons, 6 electrons Isotope Maker 2.3

19. Average Atomic Mass • Average Atomic Mass of an element is the weighted average of an element’s naturally occurring isotopes. • What is the average mass of cesium given the percent abundance of selected cesium isotopes? 75% Cs-133 20% Cs -132 5% Cs- 134

20. Practice • Guide pages 3 and 4 • show work set up and solve

21. Bohr Model of the Atom (planetary model) Energy Levels • Electrons revolve around the nucleus in one of several orbits/shells/ principal energy levels • Principal energy level (PEL) is the same as the period number on the periodic table • There are 7 PEL’s therefore 7 periods • PEL is designated by a quantum number (n)

22. Noble Gas Halogen Alkali Earth Metal Period Alkali Metal Group 2.4

23. Location of electron According to the Bohr model, electrons are found in shells around the nucleus • first shell maximum of 2 electrons • second shell maximum of 8 electrons • third shell max of 18 electrons • fourth shell max of 32 electrons

24. ATOMIC STRUCTURE There are two ways to represent the atomic structure of an element or compound; 1. Electronic Configuration 2. Electron dot diagrams

25. ELECTRONIC CONFIGURATION With electronic configuration elements are represented numerically by the number of electrons in their shells and number of shells. For example; Nitrogen configuration = 2 , 5 2 in 1st shell 5 in 2nd shell 14 N 7 2+5 = 7

26. ELECTRONIC CONFIGURATION Write the electronic configuration for the following elements; 20 11 8 Na O Ca a) b) c) 16 23 40 2,8,8,2 2,8,1 2,6 14 17 Si 5 Cl B d) e) f) 11 35 28 2,8,7 2,8,4 2,3

27. Valence • Valence shell is outermost occupied energy level and is the same as the period number in the periodic table • Valence electrons are the electrons in the outer energy level of an atom

28. DOT & CROSS DIAGRAMS With Dot & Cross diagrams elements and compounds are represented by Dots or Crosses to show electrons, and circles to show the shells. For example; X 14 Nitrogen X X N X N X X X 7

29. DOT & CROSS DIAGRAMS Draw the Dot & Cross diagrams for the following elements; X 35 16 X Cl O a) b) X X 17 8 X X X X X Cl X X X X X X X O X X X X X X X X X X

30. 11 protons 11 electrons 11 protons 10 electrons Na+ Na 17 protons 18 electrons 17 protons 17 electrons Cl- Cl An ion is an atom, or group of atoms, that has a net positive or negative charge. cation – ion with a positive charge If a neutral atom loses one or more electrons it becomes a cation. anion – ion with a negative charge If a neutral atom gains one or more electrons it becomes an anion. 2.5

31. 27 3+ Al ? How many protons and electrons are in 13 ? 78 2- How many protons and electrons are in Se 34 Do You Understand Ions? 13 protons, 10 (13 – 3) electrons 34 protons, 36 (34 + 2) electrons 2.5

32. A monatomic ion contains only one atom Na+, Cl-, Ca2+, O2-, Al3+, N3- A polyatomic ion contains more than one atom OH-, CN-, NH4+, NO3- 2.5

33. SUMMARY • The Atomic Number of an atom = number of protons in the nucleus. • The Atomic Mass of an atom = number of Protons + Neutrons in the nucleus. • The number of Protons = Number of Electrons. • Electrons orbit the nucleus in shells. • Each shell can only carry a set number of electrons.