1. The Development of Atomic Theory In 1803 John Dalton proposed the “Atomic Theory” 1. All matter is made up of atoms. 2. Atoms of a particular element are similar to one another. Atoms of different elements have different properties. 3. Atoms combine in simple whole-number ratios to form compounds. 4. Chemical change involves joining, separating, or rearranging atoms. Atoms are never created or destroyed in a chemical reaction. Chapter 3 Atomic Structure & the Periodic Table

2. particle mass (g) relative mass charge proton neutron electron Atoms are the building blocks of all matter. But, in the late 1800s, it became known that atoms were made up of subatomic particles.

3. Atoms have 2 regions: Nucleus - the core of the atom -contains all protons & neutrons -all the + charge & (almost) all the mass Electron Cloud -electrons (-) -space

4. J.J. Thompson (1897) “Plum Pudding” model cathode rays = negative particles “electrons”

5. Ernst Rutherford(1911) “nuclear model” http://www.mhhe.com/physsci/chemistry/essentialchemistry/flas h/ruther14.swf

6. Atomic Number = the number of protons in an atom

7. Mass Number = the number of protons & neutrons in an atom

8. Isotopic Notation – shows the symbol, Mass Number & Atomic Number of a particular Isotope of an Element Isotopes = Atoms of the same element that have different numbers of neutrons and therefore, different Mass Numbers

9. Isotopic Notation Isotope Atomic Mass p + n o e - Isotopic Number Number Notation Magnesium-24 Magnesium-25 Magnesium-26

10. Isotopic Notation Isotope Atomic Mass p + n o e - Isotopic Number Number Notation Xenon-131 Strontium-88 Potassium-39

11. Atomic Mass = weighted average of masses of all naturally- occuring isotopes of an element Isotope Atomic Massmass of Number Numberisotope abundance Magnesium-24122423.99amu78.70% Magnesium-25122524.99amu10.13% Magnesium-26122625.98amu11.17% Periodic Table Mass for Mg: 24.31 amu

12. So, we now have 3 numbers related to the mass of an atom: Mass Numbera counted number (p + n) Isotopic Massa precise measure of the mass of an isotope Atomic Massthe weighted average of the masses of all naturally-occurring isotopes of an element Example: There are 2 naturally-occurring isotopes of copper. Calculate the Atomic Mass of copper, given the following: isotopeabundancemass Cu-63 69.09% 62.928 amu Cu-65 30.91% 64.9278 amu

13. The Periodic Law and the Periodic Table Periodic Law: when elements are arranged in order of increasing atomic number, elements with similar chemical properties occur at periodic intervals.

14. Figure 3-3 p62

15. Characteristics of: Metal Metalloid Nonmetal Silver (Ag)Antimony (Sb) Sulfur (S)

16. Light & Atomic Structure When an element is heated or exposed to a high voltage, it will give off visible light.

17. “The energy of the electron is quantized” Emission Spectra Neils Bohr

18. Electron Arrangement in Atoms -electrons occupy energy levels -only certain energy levels are allowed -emission spectra occurs when electrons move from one energy level to another - the region of space about the nucleus that contains electrons of approximately the same energy is called the electron shell n = 1lowest energyclose to nucleus n = 7highest energyfar from nucleus

19. Electron Sublevels & Orbitals - each electron shell has one or more sublevels (subshells) s, p, d, f -electrons in each sublevel occupy a 3-dimensional space called an Orbital -Orbitals have unique 3-dimensional shapes -each orbital can hold 2 electrons http://dwb4.unl.edu/chemAnime/BOHRQD/BOHRQD.html

21. Each subshell contains orbitals of a particular shape. Orbitals of higher energy levels are larger and contain electrons with higher energy. Orbital shape represents a probability density for the location of electrons p orbital d orbital

22. With so many shells, subshells & orbitals available, how does an electron know where to go?

23. Orbital Diagram -fill each available orbital from the bottom to the top. -2 electrons can fit in each orbital -the 2 electrons have opposite “spin” -all the orbitals of a subshell are filled singly before any orbital gets a 2 nd electron

24. Li B Electron configuration 3 5

26. The electron configuration: - corresponds to the position of an element in the periodic table - is responsible for the chemical behavior of an element Distinguishing electron = the last electron added to the electron configuration

27. Element e- configuration Abbreviated Orbital Diagram configuration Mg 12 1s 2 2s 2 2p 6 3s 2 [Ne]3s 2 [Ne]

28. Element e- configuration Abbreviated configuration Sc 21 Elements with d electrons

29. Exceptions to the order of filling: Energy levels get closer together at higher levels Sometimes a more stable energy is attained with a single electron in the highest s subshell

30. Write the symbol for the following elements: 1s 2 2s 2 2p 6 3s 2 3p 5 [Ar]4s 2 3d 8 In the 3 rd period & has 2 electrons in the p subshell Whose distinguishing electron is 3d 4 In Group IIA & having 2 electons in the 7s subshell A Noble Gas in period 5 Has 80 total electrons

31. Classification of the Elements 1.Based on physical properties: Metals, Nonmetals, Metalloids 2.Based on electron configuration: