1. Chapter 4 The structure of the atom

2. Atom Smallest part of an element that retains the properties of the element

3. Democritus:Greek (460-370 BC) Proposed the first atomic theory called the tiny individual particles “atomos” Aristotle said that he was wrong

4. John Dalton: Eng (1766-1844) School teacher 1808- proposed the first accepted atomic theory

5. Joseph John (J.J) Thomson English physicist (1856-1940) 1897- used the cathode ray tube experiment to discover the electron Called plum pudding model

6. Robert A. Millikan American Physicist- (1868-1953) 1909- used the oil droplet experiment to determine the charge of an electron and calculate the mass of the electron 1923- Nobel Prize Thomson’s and Millikan’s works was combined to conclude there must be a positive particle- equal in charge, but more massive than the electron

7. Ernest Rutherford New Zealander (1871- 1937) 1911- Gold Foil experiment- proved the atom was mostly empty space Concluded there was small positive center and called it the nucleus “discovered” and named the nucleus 1908- Nobel Prize

8. James Chadwick English (1891-1974) 1932- discovered the neutron

9. Subatomic particles= electron, proton, neutron Nuclear forces- short range forces that hold nuclear particles together Atomic number = number of protons in an atom –In a neutral atom = # of electrons

10. Mass number Sum of the protons and neutrons in a nucleus Mass number – atomic number = neutrons

11. Average atomic mass Weighted average of the atomic masses of the naturally occurring isotopes of an element # on chart (%)(mass)+ %(mass)= average mass Example: Carbon mass number exact weight percent abundance 1212.0098.90 1313.001.10 (12.00) (0.98) + (13.00) (0.01) = 12.011

12. isotope Same element, same number protons, same number electrons, different number of neutrons

13. Methods of writing isotopes Nuclear form and hyphen form Nuclear form= Mass atomic # 12 6 C Hyphen= name-mass Ex. Carbon-12, carbon-14

14. Atomic mass unit (AMU) 1/12 of the mass of a C-12 atom Not exactly 1 proton or 1 neutron

15. Nuclear reactions Reactions which involve as change in an atoms nucleus

16. Radioactivity Substances spontaneously emitting radiation Radiation- rays and particles Radioactive substances decay until they become stable

17. 4 types of radiation 2.Beta particle- fast moving electron 3. Gamma rays- high energy radiation 4.Positron- same mass as electron with (+) charge Proton decays to a positron and a neutron 1.Alpha particle- a helium nucleus 2 protons and 2 neutrons 0 -1 e 4242 He

18. The Mole Equal to the number of particles in exactly 12g of carbon-12

19. 3 equivalents of 1 mole 1.Molar mass: gram atomic mass, formula mass, molecular mass Mass number from chart Add for compounds Calculate the molar mass of Al(NO 3 ) 3 (1 x 27) + (3 x 14) + (9 x 16) = 213.00 g/mol 213.00 grams is the mass of one mole of aluminum nitrate. 213.00 grams of aluminum nitrate contains 6.02 x 10^23 entities of Al(NO 3 ) 3

20. 2. Avogadro’s number of representative particles 6.022 x 10 23 Elements = atoms Ionic = formula units Covalent = molecules Ex: One mole of donuts contains 6.022 x 10 23 donuts

21. 3. 22.4 L of a gas at STP Standard temp= 0 o C, 273 K Standard pressure= 1atm, 760 mmHg, 760 torr, 101.325 kPa