Ernest Rutherford (1871-1937)

1. Ernest Rutherford (1871-1937) • Won the Nobel Prize in Chemistry in 1908 • “It was quite the most incredible event..... It was almost as if a gunner were to fire a shell at a piece of tissue and the shell bounced right back!!!!! ”

2. Figure 2.7: Alpha-particle scattering from metal foils.

3. Figure 2.8: Representation of the scattering of alpha particles by a gold foil.

6. Fig. 2.13

7. Figure 2.9: A representation of two isotopes of carbon.

8. Atomic Definitions I: Symbols, Isotopes,Numbers A X The Nuclear Symbol of the Atom, or Isotope Z X = Atomic symbol of the element, or element symbol A = The Mass number; A = Z + N Z = The Atomic Number, the Number of Protons in the Nucleus N = The Number of Neutrons in the Nucleus Isotopes = atoms of an element with the same number of protons, but different numbers of Neutrons in the Nucleus

9. Depicting the Atom Fig. 2.14

10. Neutral ATOMS • 51 Cr = P+ (24), e- (24), • N (27) • 239 Pu = P+(94), e- (94), • N (145) • 15 N = P+(7), e-(7), N(8) • 56 Fe = P+(26), e-(26), • N (50) • 235 U =P+(92), e-(92), • N (143)

11. Isotopes of Hydrogen • 11H 1 Proton 0 Neutrons 99.985 % 1.00782503 amu • 21H (D) 1 Proton 1 Neutron 0.015 % 2.01410178 amu • 31H (T) 1 Proton 2 Neutrons -------- ---------- • The average mass of Hydrogen is 1.008 amu • 3H is Radioactive with a half life of 12 years. • H2O Normal water “light water “ • mass = 18.0 amu , BP = 100.000000C • D2O Heavy water • mass = 20.0 amu , BP = 101.42 0C

12. Element #8 : Oxygen, Isotopes • 168O 8 Protons 8 Neutrons • 99.759% 15.99491462 amu • 178O 8 Protons 9 Neutrons • 0.037% 16.9997341 amu • 188O8 Protons 10 Neutrons • 0.204 % 17.999160 amu

13. Calculating the “Average” Atomic Mass of an Element Problem: Calculate the average atomic mass of Magnesium! Magnesium Has three stable isotopes, 24Mg ( 78.7%); 25Mg (10.2%); 26Mg (11.1%). 24Mg (78.7%) 23.98504 amu x 0.787 = 18.876226 amu 25Mg (10.2%) 24.98584 amux 0.102 = 2.548556 amu 26Mg (11.1%) 25.98636 amu x 0.111 = 2.884486 amu 24.309268 amu With Significant Digits = 24.3 amu

14. Problem: Calculate the abundance of the two Bromine isotopes: 79Br = 78.918336 g/mol and 81Br = 80.91629 g/mol , given that the average mass of Bromine is 79.904 g/mol. Plan: Let the abundance of 79Br = X and of 81Br = Y and X + Y = 1.0 Solution: X(78.918336) + Y(80.91629) = 79.904 X + Y = 1.00 therefore X = 1.00 - Y (1.00 - Y)(78.918336) + Y(80.91629) = 79.904 78.918336 - 78.918336 Y + 80.91629 Y = 79.904 1.997954 Y = 0.985664 or Y = 0.4933 X = 1.00 - Y = 1.00 - 0.4933 = 0.5067 %X = % 79Br = 0.5067 x 100% = 50.67% = 79Br %Y = % 81Br = 0.4933 x 100% = 49.33% = 81Br

15. Modern Reassessment of the Atomic Theory 1. All matter is composed of atoms. Although atoms are composed of smaller particles (electrons, protons, and neutrons), the atom is the smallest body thatretains the unique identityof the element. 2. Atoms of one element cannot be convertedinto atoms of another element ina chemical reaction. Elements can only be converted into other elements in Nuclear reactions in which protons are changed. 3. All atoms of an element have the same number of protons and electrons, which determines the chemical behavior of the element. Isotopes of an element differ in the number of neutrons, and thus in mass number, but a sample of the element is treated as though its atoms have anaveragemass. 4. Compounds are formed by the chemical combination of two or more elements in specific ratios, as originally stated by Dalton.

16. Definitions • ELEMENT - A substance that cannot be separated into simpler substances by chemical means • COMPOUND - A substance composed of atoms of two or more elements chemically united in fixed proportions • PERIODIC TABLE - “MENDELEEV TABLE” - A tabular arrangement of the elements, vertical groups or families of elements based upon their chemical properties - actually combining ratios with oxygen

17. Fig. 2.16

18. Fig. 2.17

19. The Periodic Table of the Elements Most Probable Oxidation State +1 0 +2 +3 +_4 - 3 - 2 - 1 H He Li Be B C N O F Ne +3 +4 +5 +1 + 2 Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cu Zn Ga Ge As Se Br Cr Mn Fe Co Ni Kr Rb Sr Zr Nb Ag I Mo Tc Ru Rh Pd Xe Y Cd In Sn Sb Te Ba Au Hg W Re Os Ir Pt Rn Cs La Hf Ta Tl Pb Bi Po At Fr Ra Ac Rf Du Sg Bo Ha Me +3 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr +3

20. Groups in the Periodic Table Main Group Elements (Vertical Groups) Group IA - Alkali Metals Group IIA - Alkaline Earth Metals Group IIIA - Boron Family Group IVA - Carbon Family Group VA - Nitrogen Family Group VIA - Oxygen Family (Calcogens) Group VIIA - Halogens Group VIIIA - Noble Gases Other Groups ( Vertical and Horizontal Groups) Group IB - 8B - Transition Metals Period 6 Group -Lanthanides (Rare Earth Elements) Period 7 Group - Actinides

21. Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr The Periodic Table of the Elements H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Rf Du Sg Bo Ha Me The Halogens The Alkali Metals The Alkaline Earth Metals The Noble Gases

22. Figure 2.14: A modern form of the periodic table.

23. Chemical Compounds and Bonds Chemical Bonds - The electrostatic forces that hold the atoms of elements together in the compound. Covalent Compounds - Electrons are shared between atoms of different elements to form Covalent Cpds. Ionic Compounds - Electrons are transferred from one atom to another to form Ionic Cpds. “Cations” - Metal atoms lose electrons to form “ + ” ions. “Anions” - Nonmetal atoms gain electrons to form “ - ” ions. Mono-atomic ions form binary ionic compounds

24. Figure 2.16: Molecular and structural formulas and molecular models.