Periodic Table of Elements

1. Periodic Table of Elements Dr Seemal Jelani

2. Dr Seemal Jelani

3. The proidic Table • A “periodic table” is an arrangement of elements in which the elements are separated into groups based on a set of repeating properties • The periodic table allows you to easily compare the properties of one element to another Dr Seemal Jelani

4. 4 Main Blocks

5. Mendeleev’s Periodic Law • Properties of the elements is a periodic function of their atomic mass

6. Why Mendeleev’s basic version of the periodic chart? • Mendeleev/Meyer periodic chart is the basis of today’s chart because it: • Predicts Atomic Properties • Indicates Trends • Indicates groups that will react/not react together

7. Mendeleev noticed that the chemical properties of the elements repeated each time he started a new row. • Mendeleev made two interesting observations 1. Mendeleev’s table contains gaps that elements with particular properties should fill. 2. The elements do not always fit neatly in order of atomic mass. • Mendeleev predicted the properties of the missing elements.

8. More Periodic Table • Period - rows of elements with the same energy level • Groups - elements in the same column with the same electron configuration • Metals- left of metalloids • Nonmetals- rt of metalloids

9. Majority of elements are metals

10. Special names for Some Main Groups • Four groups within the main-group elements have special names. These groups are: • alkali metals(Group 1) • alkaline-earth metals(Group 2) • halogens(Group 17) • noble gases(Group 18)

11. Elements in Group 1are called alkali metals. lithium, sodium, potassium, rubidium, cesium, and francium • Alkali metals are so named because they are metals that react with water to make alkaline solutions. • Because the alkali metals have a single valence electron, they are very reactive. • In losing its one valence electron, potassium achieves a stable electron configuration. • Alkali metals are never found in nature as pure elements but are found as compounds.

12. Group 2 elements are called alkaline-earth metals. • The alkaline-earth metals are slightly less reactive than the alkali metals. • They are usually found as compounds. • The alkaline-earth metals have two valence electrons and must lose both their valence electrons to get to a stable electron configuration. • It takes more energy to lose two electrons than it takes to lose just the one electron that the alkali metals must giveup to become stable.

13. Elements in Group 17 of the periodic table are called thehalogens. • The halogens are the most reactive group of nonmetal elements. • When halogens react, they often gain the one electron needed to have eight valence electrons, a filled outer energy level. • Because the alkali metals have one valence electron, they are ideally suited to react with the halogens. • The halogens react with most metals to producesalts.

14. Group 18 elements are called the Noble gases. • The noble gas atoms have a full set of electrons in their outermost energy level. • The low reactivity of noble gases leads to some special uses. • The noble gases were once called inert gases because they were thought to be completely unreactive. • In 1962, chemists were able to get xenon to react, making the compound XePtF6. • In 1979, chemists were able to form the first xenon-carbon bonds.

15. Hydrogen • Hydrogen is in a class by itself in the periodic table • It is placed in group 1 because it has a 1+ charge and a 1s1 electron configuration • It can also be placed in Group 17 because of its behavior as well

16. Periodicity • With increasing atomic number, the electron configuration of the atoms display a periodic variation. • Which leads us to Trends

17. Ionization Energy • Amount of energy required to remove an electron from an atom • Increases across the chart • Decrease down the chart

19. Electron shielding • is the reduction of the attractive force between a positively charged nucleus and its outermost electrons due to the cancellation of some of the positive charge by the negative charges of the inner electrons.

20. Electron Affinity • The energy emitted upon the addition of an electron to an atom or group of atoms in a gas phase • Generally become more negative as you go across the chart\ • No clear trend

21. Other trends • Increase in Atomic Number and Mass • Melting and Boiling Points -metals increase L-R then decrease to nonmetals • Electronegtivity • Energy required by an element in a compound to attract an electron - increase from L-R - decrease top to bottom

22. Elements • Science has come along way since Aristotle’s theory of Air, Water, Fire, and Earth. • Scientists have identified 90 naturally occurring elements, and created about 28 others. Dr Seemal Jelani

23. Elements • The elements, alone or in combinations, make up our bodies, our world, our sun, and in fact, the entire universe. Dr Seemal Jelani

24. The most abundant element in the earth’s crust is oxygen. Dr Seemal Jelani

25. Key to the Periodic Table • Elements are organized on the table according to their atomic number, usually found near the top of the square. • The atomic number refers to how many protons an atom of that element has. • For instance, hydrogen has 1 proton, so it’s atomic number is 1. • The atomic number is unique to that element. No two elements have the same atomic number. Dr Seemal Jelani

26. 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. Dr Seemal Jelani

27. Atomic Number • This refers to how many protons an atom of that element has. • No two elements, have the same number of protons. Bohr Model of Hydrogen Atom Dr Seemal Jelani Wave Model

28. Atomic Mass • Atomic Mass refers to the “weight” of the atom. • It is derived at by adding the number of protons with the number of neutrons. This is a helium atom. Its atomic mass is 4 (protons plus neutrons). What is its atomic number? H Dr Seemal Jelani

29. Atomic Mass and Isotopes • While most atoms have the same number of protons and neutrons, some don’t. • Some atoms have more or less neutrons than protons. These are called isotopes. • An atomic mass number with a decimal is the total of the number of protons plus the average number of neutrons. Dr Seemal Jelani

30. (3.1) Groups of Elements in the Periodic Table • Eight Groups (the 7 groups of representative elements and the group of noble gases): • I. Alkali metals: (H), Li, Na, K, Rb, Cs • II. Alkali earth metals: Be, Al, Ca, Sr, Ba, Ra • III. Boron family: B, Al, Ga, In, Tl • IV. Carbon family: C, Si, Ge, Sn, Pb • V. Nitrogen family: N, P, As, Sb, Bi • VI. Chalcogens O, S, Se, Te, Po • VII. Halogens F, Cl, Br, I, At • VIII. Noble gases: (He), Ne, Ar, Kr, Xe, Rn • Representative metals (I and II) and non-metals (VI and VII).

31. Properties of Metals • Metals are good conductors of heat and electricity. • Metals are shiny. • Metals are ductile (can be stretched into thin wires). • Metals are malleable (can be pounded into thin sheets). • A chemical property of metal is its reaction with water which results in corrosion. Dr Seemal Jelani

32. Properties of Non-Metals • Non-metals are poor conductors of heat and electricity. • Non-metals are not ductile or malleable. • Solid non-metals are brittle and break easily. • They are dull. • Many non-metals are gases. Sulfur Dr Seemal Jelani

33. 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. Silicon Dr Seemal Jelani

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36. Families Periods • 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. • 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. Dr Seemal Jelani

37. Families Dr Seemal Jelani

38. Hydrogen • The hydrogen square sits atop Family Li, 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. Dr Seemal Jelani

39. 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. Dr Seemal Jelani

40. 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. Dr Seemal Jelani

41. 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. Dr Seemal Jelani

42. 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.) Dr Seemal Jelani

43. Atoms bond until this level is complete • Atoms with few valence electrons lose them during bonding • Atoms with 5, 6, 7,valence electrons gain electrons during bonding. Dr Seemal Jelani

44. 5 Dr Seemal Jelani

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46. Dr Seemal Jelani

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

48. 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. Dr Seemal Jelani

49. 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. Dr Seemal Jelani

50. 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. Dr Seemal Jelani