The Periodic Table

1. The Periodic Table Chapter 6.1

2. Periodicity • something that repeats in a specific manner.

3. Lists of known elements • In the 1790s Lavoisier complied a list of known elements (23) • Many new elements were discovered in the 1800s • electricity allowed compounds to be broken into elements • industrial revolution led to chemistry based industries • spectrometer allowed elements to be identified

4. 1860-1870 • In the 1860s chemists agreed on a method to accurately determine atomic mass • By 1870 there were 70 known elements • chemists were overwhelmed learning the properties of so many new chemicals • think of a Walmart where nothing is organized. It’s all just thrown wherever and you have to search through all of it.

5. John Newlands • arranged elements by increasing atomic mass and realized properties were repeated after every 8th element. He called this the law of octaves (just like music): • element 1 and element 9 behaved similarly

6. John Newlands • harshly criticized for his analogy to music • his rows became column in our periodic table

7. Dmitri Mendeleev • showed a connection between atomic mass and properties • arranged elements by increasing atomic mass in columns and grouped by physical and chemical properties

8. Dmitri Mendeleev • predicted the existence and properties of unknown elements • He left gaps for these unknown elements • some elements were ordered incorrectly

9. Henry Mosely • discovered each element has a unique number of protons • arranged elements by increasing atomic number (protons)

10. Henry Mosely • saw clear periodic pattern of elements (periodic law) • brought order to seemingly unrelated facts

11. When elements are arranged in order of increasing atomic number, there is a periodic pattern in their physical and chemical properties. Periodic Law

12. Boxes in the Periodic Table • each box gives: • element name • element symbol • atomic number (= number of protons) • atomic mass (weighted average mass of all isotopes of that element)

13. Periods: • horizontal rows ( ) on the periodic table • there are 7 periods • the periods correspond with the number of electron shells or energy levels • As you go from left to right across a period, the number of protons (atomic number) increases by 1.

14. Groups/Families: The vertical columns on the periodic table. The elements in any group of the periodic table have similar physical and chemical properties because they have the same number of valence electrons!

15. Question! How are periods and groups/families on the periodic table different? Use this sentence stem: One way periods and groups/families on the periodic table are different is …….

16. Modern Periodic Table • Group A elements are called representative elements • Group B elements are called transition elements

17. Classification Groups • elements can be classified as: • metals • nonmetals • metalloids • divides along the zigzag line

19. Metals • On the left side of the periodic table: • Exception: Hydrogen IS NOT a metal • High luster (shiny) • solids at room temperature • Good conductors electricity and heat • Ductile (forms wires) • Malleable (bendable/shapable) • all group B elements are metals

20. Alkali Metals

21. Alkali Metals • Soft, shiny metals that can be cut with a butter knife • alkaline means base (high pH) • group 1A elements (except hydrogen) • very reactive elements • Reacts violently with water • never found as elements in nature (always in a compound)

22. Alkali Metals • Alkali Metal Video

23. Alkaline Earth Metals

24. Alkaline Earth Metals • group 2A elements • reactive, but slightly less reactive than alkali metals (group 1A) • found in the earth’s crust • Emeralds are made of beryllium

26. Transition Metals

27. These elements are also called the rare-earth elements. InnerTransition Metals

28. Transition Elements • transition metals • conduct heat and electricity • high luster when polished • inner transition metals • lanthanide series (phosphors that emit light when struck by electrons. how television works) • actinide series (along the bottom)

30. Nonmetals • shown in yellow in your textbook • upper right hand corner of periodic table • gases or dull looking brittle solids • do NOT conduct heat or electricity well • Br is the only liquid nonmetal

31. Halogens

32. Halogens • Group 7A elements • extremely reactive • halogen comes from a Greek word meaning giving rise to salt • combine with other elements to form salts

33. Noble Gases

34. Noble Gases • Group 8A • All gases • Unreactive: inert, stable, don’t form compounds • Have complete valence shells

36. Metalloids • shown in green boxes in your textbook • along the stair step line • have physical and chemical properties that are • metal like • nonmetal like • Silicon is used in computer chips • Germanium is used in solar cells

37. Periodic Trends

38. Atomic Radii • Atomic radius – one half the distance between the nuclei of two atoms of a molecule.

40. Atomic Radii • Decrease across the periods. • Caused by the increasing positive charge of the nucleus • Increase down the group ( A few exceptions) • Outer electron is in higher energy levels – farther from the nucleus.

41. Group trends H • As we go down a group • Each atom has another energy level (electron shell), • So the atoms get bigger. Li Na K Rb

42. Ionic Radii • Ion: an atom or a bonded group of atoms that has a charge • Cation – positive ion • Loss of electron; decrease in radius (smaller) • Protons pull harder on the electrons to pull them in tight • Anion – negative ion -Gain of electron; increase in radius (larger) -the nucleus is less powerful than the electron cloud so it expands.

43. Ionic Radii • Metals on the left form cations • Nonmetals on the right form anions • As you move to the right on the Periodic Table, the size of an ion decreases. • As you move down a column, the size of an ion increases

44. Question • What is the difference between atomic radius and ionic radius? • Write this Stem in your notes: The difference between atomic and ionic radius is …… • When you are finished writing, put pencil down and look up. • When everyone is finished, we will share.

45. Ionization Energy • The energy required to remove an electron from an atom • As you move across a period, the ionization energy increases. • Down the Groups, the ionization energy decreases. • Caused by the increased size of the atoms. The electrons that are farther from the nucleus are easier to remove

46. Ionization Energy

47. Another Way to Look at Ionization Energy

48. Electronegativity Table of the Elements Electronegativity • The pull a nucleus has on the electrons of a neighboring atom during a chemical bond. • Metals lose electrons so they have low electronegativity's. • Non-metals gain electrons so they have high electronegativity's (exception: noble gases are NOT electronegative) • Generally, electronegativity increases from left to right and decreases from top to bottom. Periodic table of electronegativity using the Pauling scale See also Periodic table

49. Electronegativity

50. Summation of Periodic Trends