CHEMISTRY The Molecular Science Chapter two

1. CHEMISTRYThe Molecular ScienceChapter two Slides prepared by S. Michael Condren Department of Chemistry Christian Brothers University to Accompany CHEMISTRY The Molecular Science by John W. Moore, Conrad Stanitski, & Peter C. Jurs

2. Chapter 2 Elements & Atoms

3. Atomic Structure Electrical charges of the same type repel one another, and charges of the opposite type attract one another.

4. Radioactivity

5. Alpha Radiation • composed of 2 protons and 2 neutrons • thus, helium-4 nucleus • +2 charge • mass of 4 amu • creates element with atomic number 2 lower

6. Beta Radiation • composed of a high energy electron which was ejected from the nucleus • “neutron” converted to “proton” • very little mass • -1 charge • creates element with atomic number 1 higher

7. Gamma Radiation • nucleus has energy levels • energy released from nucleus as the nucleus changes from higher to lower energy levels • no mass • no charge

8. electrons found in electron cloud relative charge of -1 relative mass of 0.00055 amu protons found in nucleus relative charge of +1 relative mass of 1.0073 amu neutrons found in nucleus neutral charge relative mass of 1.0087 amu Structure of the Atom

9. Millikan’s Experiment

10. Rutherford’s Experiment

11. Rutherford’s Model of the Atom • atom is composed mainly of vacant space • all the positive charge and most of the mass is in a small area called the nucleus • electrons are in the electron cloud surrounding the nucleus

12. Ions • charged single atom • charged cluster of atoms

13. Ions • cations • positive ions • anions • negative ions • ionic compounds • combination of cations and anions • zero net charge

14. Metric Prefixes

15. Relative size of atom and atomic nucleus

16. Scanning Tunneling Microscope

17. Measurement and Units length - meter volume - liter mass - gram

18. Atomic number, Z • the number of protons in the nucleus • the number of electrons in a neutral atom • the integer on the periodic table for each element

19. Isotopes • atoms of the same element which differ in the number of neutrons in the nucleus • designated by mass number

20. Isotopes of Hydrogen H-1, 1H, protium • 1 proton and no neutrons in nucleus • only isotope of any element containing no neutrons in the nucleus • most common isotope of hydrogen

21. Isotopes of Hydrogen H-2 or D, 2H, deuterium • 1 proton and 1 neutron in nucleus

22. Isotopes of Hydrogen H-3 or T, 3H, tritium • 1 proton and 2 neutrons in nucleus

23. Mass Number, A • integer representing the approximate mass of an atom • equal to the sum of the number of protons and neutrons in the nucleus

24. Nuclear Notation X-A • C-12 XA • C12 ZXA • 6C12

25. Masses of Atoms Carbon-12 Scale Masses of the atoms are compared to the mass of C-12 isotope having a mass of 12.0000

26. Mass Spectrometer

27. Atomic Masses andIsotopic Abundances natural atomic masses = sum[(atomic mass of isotope)  (fractional isotopic abundance)]

28. The Mole • a unit of measurement, quantity of matter present • Avogadro’s Number 6.022  1023 particles • Latin for “pile”

29. Molar Mass Sum atomic masses represented by formula atomic masses  gaw molar mass  MM

30. Example How many grams of Cu are there in 5.67 mol Cu? #g Cu = (5.67 mol)(63.546g/mol) = 360. g Atomic mass of Cu

31. Example Calculate the number of boron atoms in1.000gsample of the element. #B atoms = (1.000g)(1mol / 10.81g)  (6.022  1023atoms/mol) = 5.571  1022 B atoms

32. Example How many moles of silicon, S, are in 30.5g of S? #mol Si = (30.5g)(1 mol/32.06g) = 0.951 mol Si

33. Example What is the molar mass of methanol, CH3OH? MM = 1(gaw)C + (3 + 1)(gaw)H + 1(gaw)O = 1(12.011)C + 4(1.00794)H + 1(15.9994)O = 22.042 g/mol

34. Example How many moles of carbon dioxide molecules are there in 6.45g of carbon dioxide? MM = 1(gaw)C + 2(gaw)O = 44.01 g/mol #mol CO2 = (6.45g)(1 mol/44.01g) = 0. 147 mol

35. Development of Periodic Table Newlands - English 1864 – Law of Octaves – every 8th element has similar properties

36. Development of Periodic Table Mendeleev • Russian • 1869 - Periodic Law • allowed him to predict properties of unknown elements

37. Mendeleev’s Periodic Table the elements are arranged according to increasing atomic weights Missing elements: 44, 68, 72, & 100 amu

38. Predicted Properties of Ekasilicon

39. Modern Periodic Table Moseley, Henry Gwyn Jeffreys 1887–1915, English physicist. • studied the relations among spectra of different elements. • concluded that the atomic number is equal to the charge on the nucleus based on the x-ray spectra emitted by the element. • explained discrepancies in Mendeleev’s Periodic Law.

40. Modern Periodic Table the elements are arranged according to increasing atomic numbers

41. Periodic Table of the Elements

42. Organization of Periodic Table • period – horizontal row • group – vertical column

43. Family Names Group IA alkali metals Group IIA alkaline earth metals Group VIIA halogens Group VIIIA noble gases transition metals inner transition metals • lanthanum series rare earths • actinium series trans-uranium series

44. Types of Elements metals nonmetals metalloids – semimetals