Intro to the periodic table

1. Intro to the periodic table Unit 5

2. Mendeleev and the first periodic table • Middle of the 19th century, • Dmitri Mendeleev organized the known elements based on their properties their atomic masses

3. Mendeleev’s first sketch of the periodic table and the first published periodic table (1869)

4. Did you notice there are some blanks on Mendeleev’s first periodic table??? • He was so confident that his organization of elements showed repeating properties that He was able to predict undiscovered elements!!

5. Two problems with the first P table • 1. Why could most of the elements be arranged in order of increasing mass but a few could not? • 2. What was the reason for chemical periodicity (why did properties repeat)?

6. The Answer • 40 years later • Henry Moseley organized the periodic table by atomic number (number of protons) • Elements fit into groups better

7. The Modern Periodic table • Is organized in order of increasing atomic number

8. Modern Periodic law • The discovery and use of atomic numbers to organize the p. table led to the Periodic Law: chemical and physical properties of elements repeat periodically when elements are arranged by atomic number

9. Groups And periods -Groups/ families: vertical columns, have similar properties -Periods:horizontal rows

10. Representative Elements • All of the elements found in group 1,2, 13-18 are called the Representative elements • Why? • Represent all 3 types of elements, metals, nonmetals and metalloids

11. Representative Elements

12. Types of Elements • Metals • A metalis an element that is a good electrical conductor and a good heat conductor. • TO THE LEFT OF STARICASE • Some properties of metals • most are solids at room temperature • Malleable • ductile • conduct electricity and heat well

13. Types of Elements • Nonmetals • A nonmetal is an element that is a poor conductor of heat and electricity. • TO RIGHT OF STAIRCASE • Some properties of nonmetals • many are gases • solids are brittle • poor conductors of heat and electricity

14. Metalloids • Metalloids • A metalloid is an element that has characteristics of both metals and nonmetals • Properties of metalloids • all metalloids are solids at room temperature • semiconductors of electricity

15. Check your understanding: Would most elements on the periodic table be metals, nonmetals, or metalloids?

16. The s block • Group 1 Alkali metals • MOST reactive metals • Not found in nature as free elements • React with water • Group 2A, Alkaline earth metals harder and denser that group 1 not as reactive as group 1

17. The d block • Groups 3-12: Transition metals • Typically less reactive than groups 1-2 so can be found as free elements in nature • aka: Group B

18. Halogens • Group 17 • The most reactive nonmetals

19. Nobel gases • Group 18: All gases • Inert (meaning unreactive; don’t form compounds because they already have all the electrons they need)

20. The bottom block • Every wonder why there are two rows of elements below the periodic table? • Inner Transition Metals, they would mess up trends if they were actually in the table so we pull them out! • Lanthanide series (top row) • Actinide series (bottom row)

21. Lanthanides • Between group 3 and 4 in the 6th period • Similar in reactivity to alkaline earth metals • Fun Fact: Lutetium has almost no applications. As a result it used to be the most expensive element in the world. These days it is easily available as a side product of other lanthanide production and its price has fallen.

22. Actinides • Between group 3 and 4 in the 7th period • All radioactive; all above Np are man made • Fun Fact: A radioactive button like this is inside most smoke detectors. A trace of americium creates charged particles that betray the smoke. Americium is thus the only man-made element available in grocery stores.

23. Periodic Trends!!

24. Valence electrons • Valence electrons: are the s, p electrons in the highest energy level • These electrons are the ones that bond!! • The group A # matches how many valence electrons

25. Valence electrons Group 13-18. # of valence electrons equal to group number - 10

26. You can Predict the charge of the ions • Octet Rule : atoms will gain or lose electrons to have a full valence shell (8 electrons)

27. Ion Size Trends • ION: an atom that has lost or gained at least one electron. • Cation: metal atom that loses e- (+) • Anion: nonmetal atom that gain e- (-)

28. ALL CATS HAVE PAWS (and are mean) (cation is positive: metals)

29. Periodic Trends • There are 4 trends of the periodic table you will need to know • Ionic Size • Atomic Size • Atomic Electronegativity • Ionization Energy

30. 1. Ion Size Trends • Cations are smaller than their neutral atoms • Because they lost an electron and energy level • Anions are larger than their neutral atoms • Because they gain electrons (which repulse one another)

31. Ionic Size Example • Ex 1: Which is larger? • Mg or Mg2+ • Ex 2: Which is larger? • S or S2-

32. Fr 2. Atomic size • Atomic size increases as you move: • from right to left in a period • from top to bottom in a group • Francium has the largest size

33. Atomic Size reason • Going from Left to Right • Gets smaller because you add more protons to nucleus and then pull in the electrons • Going Down • Gets larger because you add energies

34. Atomic Size Example • Ex. 1: Arrange the following elements in order of their decreasing size. • P(15), Mg(12), S(16)

35. 3. Electronegativity Trends • Electronegativity is a measure of the ability of an atom to attract electrons from another atom in the compound.

36. F Electronegativity Trends • Electronegativity increases as you move: • from left to right across a period • from bottom to top in a group • Fluorine (9) is the most electronegative element

37. Electronegativity Reason Electronegativity is opposite of atomic size, because the smaller the atom…the more electrons are attracted to the nucleus

38. Trends in Electronegativity Why are the noble gases not on here??!

39. Electronegativity Example • Arrange the following in order of their increasing electronegativity. • Rb(37), I(53), Sn(50)

40. 4. Ionization Energy Trends • The ionization energy is the energy needed to remove an electron from a gaseous atom. • The higher ionization energy, the harder it is to pull off electrons

41. He Ionization Energy Trends • Ionization energy increases as you move: • from left to right across a period • from bottom to top in a group • Helium (2) has the highest ionization energy

42. Ionization energy • The smaller the atom, the closer electrons are to nucleus so higher the ionization energy

43. Ionization Energy Example • Arrange the following in order of increasing ionization energy. • He(2), Xe(54), Ar(18)

44. Periodic trends summary

45. Fr Metal Reactivity Trends • Metal reactivity increases as you move: • right to left across a period • top to bottom in a group • Francium (87) is the most reactive metal

46. F Non-metal Reactivity Trends • Non-metal reactivity increases as you move: • left to right across a period • bottom to top in a group • Fluorine (9) is the most reactive non-metal

47. Reactivity Examples • Ex. 1: Which is more reactive? • Fe(26) or Co(27) • Ans: Fe • Ex. 2: Which is less reactive? • Cl(17) or F(9) • Ans: Cl