Periodic Table and Periodic Trends

1. Periodic Table and Periodic Trends Periodic Table History

2. History of the Periodic Table • 70 elements had been discovered by the mid-1800’s, but until Dmitri Mendeleev, no one had a come with a way to organize the elements. • Mendeleev came up with thefirst working system of filing the elements. • He listed the elements in columns in order of increasing atomic mass, and then put columns together that had similar chemical and physicalproperties.

3. History of the Periodic Table • Mendeleev left gaps in the table since there were no current elements that seemed to fit those spots • Those elements were eventually discovered and they fit perfectly into an open spot. • The 1st scientist that set the table in order of atomic number was Henry Moseley

4. History of the Periodic Table • The modern PT is arranged by increasing atomic number • Increases from left to right, and top to bottom • This establishes the periodic law • When the elements are arranged in order of increasing atomic #, there is a periodic repetitionof their physical & chemical properties

5. Groups- Vertical columns on the periodic table • Periods-Horizontal rows of elements- 1-7 • Periodicity- When the elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

6. Groups…Here’s Where the Periodic Table Gets Useful!! • Elements in the same group have similar chemical and physical properties!! • (Mendeleev did that on purpose.) • Why?? • They have the same number of valence electrons. • They will form the same kinds of ions (have the same ____________).

7. Groups or Families on the Periodic Table • Columns are also grouped into families. • Families may be one or several columns put together. • Families have names rather than numbers. (Just like your family has a common last name.)

8. Hydrogen • Family of its own. • Diatomic, reactive gas. • Involved in the explosion of the Hindenberg. • Promising as an alternative fuel source for automobiles

9. Alkali Metals • 1st column on the periodic table except hydrogen. • Very reactive metals, always with something else in nature (like in salt). • Soft enough to cut with a butter knife

10. Alkaline Earth Metals • Second column on the periodic table. • Reactive metals that are always combined with nonmetals. • Several are important mineral nutrients (such as Mg and Ca)

11. Representative Elements- All of the Group A Elements 1A-8A

12. Transition Metals • Elements in groups 3-12- Group B • Less reactive, harder metals • Includes metals used in jewelry and construction. • Metals used “as metal.”

13. Halogens • Elements in group 17 • Very reactive, volatile, most diatomic, nonmetals • Always found combined with others. • Used as disinfectants and to strengthen teeth.

14. The Noble Gases

15. The Noble Gases • Elements in group 18 • VERY unreactive, monatomic gases • Used in lighted “neon” signs • Used in blimps to fix the Hindenberg problem. • Have a full valence shell.

16. Periodic Table and Periodic Trends Trend # 1 Atomic Radius or Size

17. Group Trend: • The Trend: As you move downagroup on the periodic table, the atomic radius or size of an atom increases. • The Reason: This is because each row adds a new energy level for the electrons. • Examples: Which is larger: Mg or Ca Calcium!

18. Period Trend: • The Trend: As you move acrossaperiod from left to right, the atomic radius or size of an atom decreases. • The Reason: This is because of the nucleus getting largeras you add more protons. This pulls the electrons closer to the nucleus. • Examples: Which is smaller: C or F? Fluorine! Which is larger: Ba or Cs? Cs!

20. A Trick to Remembering the Trend: • Snowman standing that then falls over: • Example: Arrange the following elements in order of increasing size: Mg, Na, Rb, and Cl Cl Mg Na Rb

21. Periodic Table and Periodic Trends Trend # 2 First Ionization Energy

22. Ionization energy is the amount of energy required to remove an electron from an element in its gaseous state. Li (g) Li+(g) + e- • Ionization energy refers to making positive ions or cations. • To form a positive ion, an element will lose its valence electrons on the outermost energy level.

23. Group Trend: • The Trend: As you move downa group on the periodic table, the ionization energy of an atom decreases. • Example: Which has smaller ionization energy: Ba or Ca? Barium! Which has smaller ionization energy: I or Br? Iodine!

24. Period Trend: • The Trend: As you move acrossaperiod from left to right, the ionization energy of an atom increases. • Examples: Which is lower in ionization energy: C or F? Carbon! Which is higher in ionization energy: Na or Mg? Magnesium!

25. The Reason: • As an atom gets larger, the valence electrons are further from the nucleus, which means that the nucleus’s pull gets weaker because the electrons are farther away. • The weaker pull means that less energy is required to remove the electron.

26. Arrange the following elements in order of decreasing ionization energy: Mg, Na, Rb, and Cl Cl Mg Na Rb

27. A Trick to Remembering the Ionization Energy Trend: • Opposite of Atomic Radius: • Snowman standing on his head that then falls over: • Example: Arrange the following elements in order of increasing ionization energy Mg, Na, Rb, and Cl Rb Na Mg Cl

28. Periodic Table and Periodic Trends Trend # 3 Electronegativity

29. Electronegativity is the ability of an atom to gain an electron in a chemical bond. • Scientists have assigned values for eletronegativity that range from zero to four. The higher values represent the more electronegativeelements. • Since they are unreactive, the noble gases are not assigned electronegativity values.

30. Group Trend: • The Trend: As you move downagroup on the periodic table, the electronegativity of an atom decreases. Examples: Which is more electronegative: N or P? Nitrogen! Which has a smaller electronegativity value: F or Br? Bromine!

31. Period Trend: • The Trend: As you move across a period from left to right, the electronegativity of an atom increases. • Examples: • Which is less electronegative: C or O? Carbon! Which has a greater electronegativity: Ca or K? Ca or K? Calcium!

32. The Reason: • As an atom gets larger, the valence electrons are further from the nucleus, which means that the nucleus’s pull gets weaker as the electrons move farther away. • Smaller elements will be more electronegative because their nucleus is closer to the valence electrons and has a stronger pull on the valence electrons.

33. Example: Arrange the following elements in order of increasing electronegativity: Cd, Cl, Br, and I Cd I Br Cl

34. A Trick to Remembering the Electronegativity Trend: • Opposite atomic radius, same as Ionization energy- Snowman standing on his head and then he falls over: • Example: Arrange the following elements in order of increasing electronegativity: Cd, Cl, Br, and I Cd I Br Cl

35. Warm-Up 12-3-12 • What two properties both have the following trend? Decreases as you go down the group and Increases as you go across the period from right to left

36. Warm-Up 12-3-12 • What two properties both have the following trend? Decreases as you go down the group and Increases as you go across the period from right to left • Electronegativity • Ionization Energy

37. Periodic Table and Periodic Trends Trend # 4 Reactivty- Metals & Nonmetals

38. Reactivity of Metals • Group Trend: The Trend: For metals, the reactivity of metals increases as you move down a group. Examples: Which metal is more reactive: K or Rb? Rubidium! Which metal is more reactive: Cu or Au? Gold!

39. Period Trend: • The Trend: For metals, the reactivity of metals decreases as you move across the period from left to right. • Examples: Which metal is the least reactive: Ca or Zinc? Zinc! Arrange the following metals- Na, Mg, Al in order of decreasing reactivity. Na Mg Al

40. The Reason: • When metals react, they lose electrons. • Metals with low ionization energy are more reactive, or alkali metals are more reactive because they lose electrons more easily.

41. Reactivity of Nonmetals • Group Trend: • The Trend: For nonmetals, the reactivity of nonmetals decreases as you move down a group. • Examples: Which is more reactive: Oxygen or sulfur? Oxygen! Which halogen is the most reactive: F, Cl, Br, or I? Fluorine!

42. Period Trend: • The Trend: For nonmetals, the reactivity of nonmetals increases as you move across a period from left to right (excluding the noble gases). • Examples: • Which is more reactive: O or F? Fluorine! On period 3, which nonmetal is the most reactive? Chlorine!

43. The Reason: • When nonmetals react, they tend to gain electrons. • Nonmetals with higherelectronegativities have a stronger pull on electrons and, therefore gain electrons easily. In other words, smaller atoms tend to form negative ions more easily because the nucleus is more likely to attract these electrons.

44. A Trick to Remembering the Trends: • Snowman that falls over: Atomic Radius Metal Reactivity A&M likes to stand at football games!

45. A Trick to Remembering the Trends: • Snowman standing on his head and then he falls over: • Electronegativity **EINstein likes to do • Ionization Energy headstands!! • Nonmetal Reactivity