The Periodic Table

1. The Periodic Table Unit 3/Chapters 3 & 8 Notes Chemistry CPA

2. Unit Objectives: • To describe the contribution of the structure of the periodic table by scientists such as Dobereiner, Mendeleev, and Mosley • To describe the information given in an element square on the periodic table • To know the difference (in structure and properties) between families/groups and periods • To be able to distinguish between metals, nonmetals and metalloids and know their general location on the periodic table • To describe the general physical and chemical properties of metals and nonmetals • To be able to name and identify the properties of the following families: Alkali metals, alkaline earth metals, transition metals, boron family, carbon family, nitrogen family, oxygen family, halogens and noble gases • To be able to analyze the major trends on the periodic table: atomic radius, ionization energy, electronegativity, and electron affinity, and reactivity

3. The History of the Periodic Table

4. Dobereiner’sTriads • In 1829, Johann Wolfgang Dobereiner, a German scientist, was the first to classify elements into groups based on John Dalton's postulates. • He grouped the elements with similar chemical properties into clusters of three called 'Triads'. • The distinctive feature of a triad was the atomic mass of the middle element. • When elements were arranged in order of their increasing atomic mass, the atomic mass of the middle element was approximately the average of the other two elements of the triad.

5. Mendeleev • In 1869,Dmitri IvanovitchMendeléev created the first accepted version of the periodic table. • He grouped elements according to their atomic mass, and as he did, he found that the families had similar chemical properties.  • Blank spaces were left open to add the new elements he predicted would occur. 

6. Mendeleev’s Table

7. Mosely • Later, Henri Moseley (England, 1887-1915) established that each elements has a unique atomic number, which is how the current periodic table is organized.

8. What’s in a square? • Different periodic tables can include various bits of information, but usually: • atomic number • symbol • atomic mass • number of valence electrons • state of matter at room temperature.

9. Organization of the periodic table – Families/Groups (columns)(notes) • The vertical columns of the table are called groups or families. Element in the same group have similar but not identical characteristics • Numbered from 1 to 18. • Elements in the same group have the same number of outer shell electrons, and hence similar chemical properties.

10. Organization of the periodic table – Periods (columns) • The horizontal rows of the table are called periods. • Numbered from 1 to 7. • Each contains elements with electrons in the same outer shell. • Elements do not have similar properties in the periods like Families do.

11. More on Families and Periods… Families/Groups: Periods: Each horizontal row of elements is called a period. The elements in a period are not alike in properties. In fact, the properties change greatly across even given row. The first element in a period is always an extremely active solid. The last element in a period, is always an inactive gas. • Columns of elements are called groups or families. • Elements in each family have similar but not identical properties. • For example, lithium (Li), sodium (Na), potassium (K), and other members of family IA are all soft, white, shiny metals. • All elements in a family have the same number of valence electrons.

12. Types of elements • There are three main types of elements: metals, non metals and metalloids • 1. Metals appear on the left hand side of the zig zag line that separates the periodic table • 2. Non metals appear on the right hand side of the zig zag line that separates the periodic table • 3. Elements on either side of the zigzag line have properties of both metals and non-metals. These elements are called metalloids.

14. Properties of Metals • Most elements are metals. 88 elements to the left of the stairstep line are metals or metal like elements. • Left side of the periodic table • Positive valencies

15. Physical Properties of Metals • Luster (shininess) • Good conductors of heat and electricity • High density (heavy for their size) • High melting point • Ductile (most metals can be drawn out into thin wires) • Malleable (most metals can be hammered into thin sheets)

16. Chemical Properties of Metals • Easily lose electrons • Corrode easily. Corrosion is a gradual wearing away. (Example: silver tarnishing and iron rusting)

17. Properties of Nonmetals • Nonmetals are found to the right of the stairstep line. Their characteristics are opposite those of metals. Sulfur

18. Physical Properties of Metals • No luster (dull appearance) • Poor conductor of heat and electricity • Brittle (breaks easily) • Not ductile • Not malleable • Low density • Low melting point

19. Chemical Properties of Nonmetals • Tend to gain electrons • Since metals tend to lose electrons and nonmetals tend to gain electrons, metals and nonmetals like to form compounds with each other. These compounds are called ionic compounds. When two or more nonmetals bond with each other, they form a covalent compound.

20. Properties of Metalloids • Metalloids (metal-like) have properties of both metals and non-metals. • They are solids that can be shiny or dull. • They conduct heat and electricity better than non-metals but not as well as metals. • They are ductile and malleable.

22. Hydrogen • The hydrogen square sits atop Family AI, but it is not a member of that family. Hydrogen is in a class of its own. • It’s a gas at room temperature. • It has one proton and one electron in its one and only energy level. • Hydrogen only needs 2 electrons to fill up its valence shell.

24. Alkali Metals • The alkali family is found in the first column of the periodic table. • Atoms of the alkali metals have a single electron in their outermost level, in other words, 1 valence electron. • They are shiny, have the consistency of clay, and are easily cut with a knife.

25. Alkali Metals • They are the most reactive metals. • They react violently with water. • Alkali metals are never found as free elements in nature. They are always bonded with another element.

26. What does it mean to be reactive? • We will be describing elements according to their reactivity. • Elements that are reactive bond easily with other elements to make compounds. • Some elements are only found in nature bonded with other elements. • What makes an element reactive? • An incomplete valence electron level. • All atoms (except hydrogen) want to have 8 electrons in their very outermost energy level (This is called the rule of octet.) • Atoms bond until this level is complete. Atoms with few valence electrons lose them during bonding. Atoms with 6, 7, or 8 valence electrons gain electrons during bonding.

27. Reactivity of Metals • http://www.youtube.com/watch?v=V2TimLxskZw (Magnesium in water) • http://www.youtube.com/watch?v=nSgIr1Wba_g&feature=related(Calcium in water) • Group One (Alkaline Metals) are more reactive than Group 2 (Alkaline Earths) • As you go down a group metals become more reactive • This happens because as you go down a group atoms get larger and metals tend to donate electrons in reactions.

28. Reactivity of Non metals • Look at table 3.3 to see which Halogen is most reactive • Reactivity decreases down the group • Why? Think about atomic properties • Non metals tend to form negative ions (they gain electrons from other atoms) • Electronegativity or love of electrons is strongest with Fluorine and decreases down the group.

30. Alkaline Earth Metals • They are never found uncombined in nature. • They have two valence electrons. • Alkaline earth metals include magnesium and calcium, among others.

32. Transition Metals • Transition Elements include those elements in the B families. • These are the metals you are probably most familiar: copper, tin, zinc, iron, nickel, gold, and silver. • They are good conductors of heat and electricity.

33. Transition Metals • The compounds of transition metals are usually brightly colored and are often used to color paints. • Transition elements have 1 or 2 valence electrons, which they lose when they form bonds with other atoms. Some transition elements can lose electrons in their next-to-outermost level.

34. Transition Elements • Transition elementshave properties similar to one another and to other metals, but their properties do not fit in with those of any other family. • Many transition metals combine chemically with oxygen to form compounds called oxides.

36. Boron Family • The Boron Family is named after the first element in the family. • Atoms in this family have 3 valence electrons. • This family includes a metalloid (boron), and the rest are metals. • This family includes the most abundant metal in the earth’s crust (aluminum).

38. Carbon Family • Atoms of this family have 4 valence electrons. • This family includes a non-metal (carbon), metalloids, and metals. • The element carbon is called the “basis of life.” There is an entire branch of chemistry devoted to carbon compounds called organic chemistry.

40. Nitrogen Family • The nitrogen family is named after the element that makes up 78% of our atmosphere. • This family includes non-metals, metalloids, and metals. • Atoms in the nitrogen family have 5 valence electrons. They tend to share electrons when they bond. • Other elements in this family are phosphorus, arsenic, antimony, and bismuth.

42. Oxygen Family • Atoms of this family have 6 valence electrons. • Most elements in this family share electrons when forming compounds. • Oxygen is the most abundant element in the earth’s crust. It is extremely active and combines with almost all elements.

44. Halogen Family • The elements in this family are fluorine, chlorine, bromine, iodine, and astatine. • Halogens have 7 valence electrons, which explains why they are the most active non-metals. They are never found free in nature. • Halogen atoms only need to gain 1 electron to fill their outermost energy level. • They react with alkali metals to form salts.

46. Noble Gases • Noble Gasesare colorless gases that are extremely un-reactive. • One important property of the noble gases is their inactivity. They are inactive because their outermost energy level is full. • Because they do not readily combine with other elements to form compounds, the noble gases are called inert. • The family of noble gases includes helium, neon, argon, krypton, xenon, and radon. • All the noble gases are found in small amounts in the earth's atmosphere.

48. Rare Earth Elements • The thirty rare earth elements are composed of the lanthanide and actinide series. • One element of the lanthanide series and most of the elements in the actinide series are called trans-uranium, which means synthetic or man-made.

49. Periodic Trends • Many properties of atoms depend on the strength of attraction between the outer shell electrons and the nucleus • This attraction will depend on: • The positive charge that attracts the other shell electrons • The distance of electrons from the nucleus

50. Four Periodic Trends • Atomic Radius • Ionization Energy • Electronegativity • Electron Affinity