1. CHAPTER 4 – ELEMENTS AND ATOMS THE ELEMENTS 400 BC Greeks thought there were 4 elements: Earth, Wind, Fire, Water 2009 AD There are 117 known elements (94 that occur naturally) 2B-1 (of 40)

2. Most Common Elements in : Earth’s CrustSolid EarthAtmosphereUniverse Oxygen Silicon Aluminum Iron Nickel Magnesium Nitrogen Oxygen Argon Hydrogen Helium 2B-2

3. SYMBOLS FOR THE ELEMENTS Letters symbolize elements 1 st Letter – always a capital 2 nd Letter – always lower case Co CO Cobalt Carbon monoxide Sn S N Tin Sulfur & a little Nitrogen? Some symbols come from Latin names YOU MUST MEMORIZE THE 46 ELEMENTAL SYMBOLS ON HANDOUT 1 2B-3

4. 400 BC DEMOCRITUS Proposed that all matter is composed of indivisible particles ATOMS – From the Greek Atomos, meaning indivisible 2B-4

5. 1803 JOHN DALTON Proposed that matter is composed of atoms Atoms could explain why compounds always have a definite proportion by mass Mass of CarbonMass of Hydrogen Ethyne Ethene 12 grams1 gram 12 grams2 grams Suppose the elements carbon and hydrogen are composed of atoms Suppose carbon atoms weigh 12 times more than hydrogen atoms Ethyne is C 1 H 1 Ethene is C 1 H 2 Ethane12 grams3 grams Ethane is C 1 H 3 2B-5

6. DALTON’S ATOMIC THEORY 1 – Elements are made of individual atoms 2 – All atoms of a given element are the same 4 – Atoms of one element cannot change into atoms of another element 3 – Compounds are formed when atoms of different elements combine with each other 2B-6

7. FORMULAS OF COMPOUNDS CHEMICAL FORMULA – The representation of a compound or molecule using elemental symbols Writing formulas: 1) Each element present is represented by its elemental symbol 2) A right subscript tells the number of atoms of each element 3) Subscripts of “1” are not written CS 2 Na 3 AsO 4 Zn(NO 3 ) 2 BaCl 2. 2H 2 O 1 carbon atom 2 sulfur atoms 3 sodium atoms 1 arsenic atom 4 oxygen atoms 1 zinc atom 2 nitrogen atoms 6 oxygen atoms 1 barium atom 2 chlorine atoms 4 hydrogen atoms 2 oxygen atoms 2B-7

8. 1897 J.J. THOMSON Discovered that atoms consist of subatomic particles ELECTRONS – Negatively charged subatomic particles 2B-8

9. Thomson Model of the Atom PROTONS – Positively charged subatomic particles 2B-9

10. 1910 ERNEST RUTHERFORD Found that the atoms has a small, positively charged core which contains almost all of the atom’s mass 2B-10

11. Rutherford Model of the Atom NUCLEUS – The dense, positive core of the atom that contains protons 2B-11

12. 1932 JAMES CHADWICK Discovered a third subatomic particle This subatomic particle was found the in nuclei of atoms NEUTRONS – Neutral subatomic particles 2B-12

13. Around Nucleus-1 Nucleus+1836 Nucleus01839 LocationChargeRelative Masses Electron Proton Neutron The Nuclear Model of the Atom 2B-13

14. 1964 MURRAY GELL-MANN Proposed that protons and neutrons are made of smaller particles called QUARKS 2B-14/15

15. All atoms of a given element contain the same number of protons ISOTOPES ATOMIC NUMBER (Z) – The number of protons in an atom ← Atomic Number ← Atomic Symbol Any atom with 1 proton is a hydrogen atom Because atoms are electrically neutral, the number of electrons must equal the number of protons 2B-16

16. All 3 are hydrogen atoms because they each have 1 proton ISOTOPES – Atoms of the same element (same number of protons), but with different numbers of neutrons MASS NUMBER (A) – The sum of the protons and neutrons in an atom Hydrogen 2B-17

17. Protons Neutrons Electrons 111111 012012 111111 Isotope Name 1 H Hydrogen-1 2 H Hydrogen-2 3 H Hydrogen-3 Mass Numbers ARE NOT found on the Periodic Table 123Mass Number 2B-18

18. Protons Neutrons Electrons2 12122 Isotope Name 3 He Helium-3 4 He Helium-4 34Mass Number 2B-19

19. Protons Neutrons Electrons Isotope Name 27 Al 238 U Find the number of protons, neutrons, and electrons in each: 2B-20

20. An arrangement of the chemical elements in order of atomic number, with elements having similar properties placed in columns THE PERIODIC TABLE 2B-21

21. 1869 DMITRI MENDELEEV Developed the first periodic table 2B-22

22. PERIOD or SERIES – A rowGROUP or FAMILY – A column Elements in columns have similar properties because they have the same number of valence electrons 2B-23

23. METALS Physical Properties – Metallic luster, malleable, ductile, conductors of heat and electricity Solids are brilliant white (or silver) except copper (red) and gold (yellow), mercury is a liquid 2B-24

24. NONMETALS Physical Properties – Opposite of metals Some are crystalline solids, bromine is a liquid, and some are gases 2B-25

25. METALLOIDS Properties of metals and nonmetals Border the diagonal line separating the metals and nonmetals 2B-26

26. Hydrogen-A group of its own Group 1 -Alkali Metals Group 2 -Alkaline Earth Metals Group 7 -Halogens Group 8-Noble Gases Middle Block-Transition Metals Extra Block-Inner Transition Metals (Lanthanides and Actinides) Cu, Ag, Au, Pt-Noble Metals 2B-27

27. NATURAL STATE OF MATTER Most elements are ACTIVE, so they easily form compounds Matter is mostly a mixture of compounds, not elements INERT elements can be found in their elemental form 1)Noble Metals:Cu, Ag, Au, Pt 2)Noble Gases:He, Ne, Ar, Kr, Xe, Rn To see any other element in its elemental state, compounds must be decomposed 2B-28

28. METALS In their elemental state, metals consist of billions of atoms bonded together This strong chemical bonding causes most metals to be solids 2B-29

29. NONMETALS In their elemental state, most nonmetals consist of a small number of atoms bonded together, while a few consist of billions of atoms bonded together MOLECULE – A group of nonmetal atoms bonded together Molecules weakly attract, so molecular matter often exists in the gaseous state, but the molecules may attract each other enough to form solids or liquids 2B-30

30. 7 of the nonmetals that exist as molecules produce DIATOMIC MOLECULES 2B-31

31. Some elements have several forms in the elemental state 1)Oxygen:dioxygen (O 2 ) and ozone (O 3 ) 2)Carbon:diamond, graphite, buckminsterfullerene ALLOTROPES – Different forms of a given element due to different interatomic bonding 2B-32

32. IONS Atoms can gain or lose electrons ION – An atom with a positive or negative charge because it has gained or lost electrons 2B-33

33. 3 Protons 3 Electrons Cations have the same name as their corresponding atom Cations are created when metals form compounds with nonmetals Lithium (Z = 3) Lithium atomLithium ion Li → Li + + e - CATION – A positive ion LiLi + 3 Protons 2 Electrons 2B-34

34. Fluorine (Z = 9) 9 Protons 9 Electrons 9 Protons 10 Electrons Fluorine atomFluoride ion F + e - → F - FF-F- 2B-35/36 ANION – A negative ion Anions are named with an –ide ending Anions are created when nonmetals form compounds with metals

35. Many ion charges can be predicted from the Periodic Table barium Ba 2+ potassiumaluminum bromide Br - oxidephosphide 2B-37

36. REVIEW FOR TEST 46 elemental names and symbols Solid, liquid, gas Substance, element, compound Heterogeneous, homogeneous Mixture, solution Physical and chemical properties Physical and chemical changes Filtration Distillation 2B-38

37. REVIEW FOR TEST Energy Specific heat capacity Heat calculations Scientists and their work Atomic structure Protons, neutrons, electrons Atomic number, mass number Isotopes Formulas of compounds 2B-39

38. REVIEW FOR TEST Elemental abundances Periodic Table Properties of metals, nonmetals, metalloids Group names Active and inert elements Diatomic elements Allotropes Cations and anions Ion charges from the Periodic Table 2B-40