The Periodic Table

1. The Periodic Table Basic Concepts

2. 1800ish--Johann Dobereiner -- triads 1864 -- John Newlands -- octaves 1870--Dmitrii Mendeleev & Lothar Meyer--by mass 1913 -- Mosley--by number of protons

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

4. Periods • 7 Horizontal rows on the table • Number of shells are equal to the number of periods.

5. Groups • 18 Vertical columns on the table • All groups have number designations • Are also called families • Same/similar physical and chemical properties due to VALENCE ELECTRONS! • No. of groups depend on valence electrons. • Some groups have special family names based upon characteristics of elements in that group

6. Group Numbering Systems • American Method • IUPAC Method

7. Family Names • Alkali Metals (Group 1) • Alkaline Earth Metals (Group 2) • Halogens (Group 17) • Noble gases (Group 18)

8. Form metal hydroxides (strong bases) when reacting in water 2 Na + 2 HOH  2 NaOH + H2 Are generally very reactive compared to other groups of metals Have one valence electron Form cations with a +1 charge Alkali Metals (Group 1)

9. Alkali metals

10. Alkaline Earth Metals (Group 2) • Form metal hydroxides (strong bases) when reacting in water Ca + 2 HOH  Ca(OH)2 + H2 • Are not as reactive as alkali metals but are generally more reactive than transition elements • Have two valence electrons • Form cations with a +2 charge

11. Alkaline earth metals

12. Halogens (Group 17) • Form a multitude of salts • Are generally very reactive when compared to other nonmetals • Have seven valence electrons • Form anions with a -1 charge

13. Halogens

14. Noble Gases (Group 18) • Are generally unreactive (inert) • Have eight valence electrons • Some compounds with xenon and krypton have been synthesized

15. Modern Periodic Table

16. Regions of the Periodic Table Metals Nonmetals Metalloids (semi-metals) Transition metals Inner-transition metals Lanthanide Series Actinide Series

17. Metals

18. 1) Metals- high luster, good conductors, ductile, malleable, most are solid at room temp (except Hg is liquid) 2)Nonmetals- low luster, poor conductors, very brittle, various states of matter at room temperature (ex: S is solid, O is gas, Br is liquid) 3) Metalloids- sit on stair-step line b/w metals and non-metals; have properties between metals and non-metals

19. Nonmetals

20. Metalloids

21. Transition Metals

22. Inner-Transition Metals

23. Periodic Table Properties and Trends

24. PERIODIC PROPERTIES • The properties which appear at regular intervals in the periodic table are called periodic properties due to similar valence electrons.

25. Common Periodic Properties • Atomic Radius • Ionization Energy • Electron Affinity • Ionic Radius • Electronegativity • Metallic Character • Nonmetallic Character

26. Atomic Radii Trends on the Periodic Table For the main group elements: • atomic radii increase going down a group • decrease going across a period.

27. Going down a group radii increases • Energy level is added for each successive period • Each energy level shields (blocks) the influence of the nucleus

28. Periodic table trends 1) Atomic Radii: As you move down a group, atomic radius increases. WHY? - The number of energy levels increases as you move down a group   Each subsequent energy level is further from the nucleus than the last. 

29. 2) As you move across a period, atomic radius decreases. WHY? - As you go across a period, electrons are added to the same energy level.  At the same time, protons are being added to the nucleus.  The concentration of more protons in the nucleus creates a "higher effective nuclear force."  In other words, there is a stronger force of attraction pulling the electrons closer to the nucleus resulting in a smaller atomic radius.

30. Points to note • Cesium has the largest atomic radius. • Fluorine has the smallest atomic radius. • Noble gases have a larger atomic radius than halogens since in inert gases the outer shell- is completely filled resulting in a force of repulsion which increases the atomic radius.

31. Ionization Energy The amount of energy required to remove one or more electron from the valency shell of an isolated gaseous atom. Ao(g) + energy => A+(g) + e - Each atom can have a series of ionization energies, since more than one electron can always be removed (except H).

32. First Ionization Energy Trends on the Periodic Table First ionization energies generally increase across a period and decrease down a group. Generally, the larger the atom the easier it is to remove an electron and the less ionization energy required.

33. Group trends • Decreases as you move down a group • why? The outermost electrons are found in higher energy levels as one goes down the group. Since the electrons are farther from the nucleus's pull the electrons are more easily removed.

34. period trend – increases from left to right why? As the atomic number increases in a period the nucleus is becoming stronger (more protons) but no new energy levels are being added. So atoms with larger atomic numbers have nucleus's that hold onto their electrons harder.

35. Low ionization energies are typical of active metals. High ionization energies are typical of active nonmetals. Very high ionization energies are found with the Noble Gases

36. Plot of First Ionization Energies For Periods 1-4 Ionization Energy (kJ/mol)

37. Electron AffinitykJ/mol

38. Definition of Electron Affinity • The amount of energy released when one or more electron is added to the outermost shell of an isolated gaseous atom. • As a result of the addition of another electron, anion will be formed • Affinity and ionization energy generally have a direct relationship: high affinity equals high ionization energy

39. Factors affecting electron affinity • Smaller the atom, greater is the electron affinity Example: Halogens with smaller atomic size have higher electron affinity. Alkali metals with larger atomic radii have low electron affinity.

40. Cont. • Electron affinity increases with an increase in nuclear charge. Ex: Cl has a greater electron affinity than Sulphur. • The electron affinity of elements having completely filled orbitals or less than half filled orbitals is practically zero.

41. Group Trends • Generally, electron affinities decrease going down the groups Because -Atomic size increases -Effective nuclear force decreases

42. Period Trends • Generally, electron affinity increases going across periods from left to right. • Metals do not tend to become anions as much as nonmetals do. • Do you see Na- or K- often?

43. Electronegativity + – 0 0 H Cl H H

44. + – H Cl Electronegativity • Electronegativity describes how electrons are shared in a compound • Consider the compound HCl • The electron clouds represent where the two electrons in the HCl bond spend their time (sizes of atoms are not being shown) • The shared electrons spend more time around Cl than H. In other words Cl is more electronegative than H.

45. ELECTRO - NEGATIVITY Say it to yourself a few times in your head. It’s a really cool word and you are going to know it real soon too. Impress your friends with new sayings like: “Your electro-negativity is really getting on my nerves.” or “My goodness! I can feel your electro-negativity all the way over here!”

46. Electro-negativity Is the tendency of an atom to attract electrons to itself when combined in a compound. It’s measured on the Linus Pauling electro-negativity scale.

47. Fluorine and E-N • Fluorine tops out the scale at 4.0 • It’s a totally arbitrary scale, based upon Fluorine at 4.0. All other atoms are compared with fluorine. • All the other electro-negativity values are relative to Fluorine.

48. Dr. Linus PaulingThat’s him at age 2. Because of his dynamic personality and his many accomplishments in widely diverse fields, it is hard to define Linus Pauling adequately. A remarkable man who insistently addressed certain crucial human problems while pursuing an amazing array of scientific interests, Dr. Pauling was almost as well known to the American public as he was to the world's scientific community. He is the only person ever to receive two unshared Nobel Prizes, one for Chemistry (1954) and for Peace (1962).

49. Linus Pauling always emphasized the importance of having a full and happy personal life. To have met this man must have been quite an honor, he would have made a fine guest for dinner. In addition to the general recognition as one of the two greatest scientists of the 20th century, he was usually acknowledged by his colleagues as the most influential chemist since Lavoisier, the 18th-century founder of the modern science of chemistry.

50. Electro-negativity is the amount of pull that an atom has for another electron in a bonding situation. Fluorine has the greatest desire of all atoms for the gain of electron. Fluorine is given the rating of 4.0 on the E-N scale, the highest electronegativity of all elements. The trend of electronegativity