2Objectives: Describe the periodic tables of Moseley and Mendeleev. Identify the various families of elements on the periodic table.State the trends in atomic radius, ionization energy, electron affinity and ion size with a group or period on the periodic table.Identify the relationship between these trends and the structure of the atom.
3History of the Periodic Table Chapter 5Section 1History of the Periodic Table
4By 1860, more than 60 elements had been discovered. Chemists needed to learn the properties of these elements as well as those of the compounds they formed.At the time there was no method for accurately determining an element’s atomic mass.Things were disorganized and confusing among chemists.
5Dmitri MendeleevMendeleev hoped to organize the elements according to their properties.He arranged the elements in order of increasing atomic mass and noticed certain similarities in their chemical properties would appear at regular intervals.In 1869 Mendeleev created the first periodic table grouping the elements with similar properties.
7Henry MoseleyIn 1911 Moseley revised the periodic table of Mendeleev by arranging the elements in order of increasing atomic number (number of protons) and not atomic mass.The elements were still grouped by similar physical and chemical properties.
8Modern Periodic TableThe periodic table has undergone extensive changes since Mendeleev’s time.More than 40 new elements have been discovered or synthesized.
9Periodic Table – an arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same column or group.
10The elements arranged vertically in the periodic table share chemical properties. Example:F, Cl, Br and I all react in a similar manner.
11Later additions to the periodic table include: Noble Gases ( ) – group 18 elements that are characterized by their relative un-reactivity.The Lanthanides (early 1900’s) – the 14 elements with atomic numbers from 58 (cerium, Ce) to 71 (lutetium, Lu)
12The Actinides – the 14 elements with atomic numbers from 90 (thorium, Th) to 103 (lawrencium, Lr). The lanthanides and actinides belong in periods 6 and 7 of the periodic table.To save space and to group them together they are set off below the main portion of the periodic table.
13Periodic Table Elements are classified in three major groups: MetalsNonmetalsMetalloidsUse the periodic table to distinguish the classes of elements
15Physical Properties of Metals MalleabilityDuctilityLusterHeat conductors and electrical conductorsSolidsEx. Iron (Fe), tin (Sn), zinc (Zn), and copper (Cu)
16Properties of Nonmetals Dull in appearanceBrittleDo not conduct electricityEx. Carbon (C), Oxygen (O)and Sulfur (S)Solids, liquids or gases
17The metalloids divide the metals from the nonmetals. They are mostly brittle solids with some properties of metals and some of nonmetals.The electrical conductivity falls between the metals and nonmetals.The metals of the p block are reactive enough to be found in nature only as compounds and not free elements (except bismuth).
18Metalloids Properties of metals and nonmetals Ex. Silicon (Si) and Germanium (Ge)Common in the computerindustry
19Summary – Section 5.1 Recognize the work of Mendeleev and Moseley. How the modern periodic table is arranged with respect to the elements.Know the three sets of elements added to the periodic table after Mendeleev.
22In the first period, the 1s sublevel is filled. The 1s sub level can hold a total of two electrons.Therefore, the first period consists of two elements - hydrogen and helium.The second period can held 8 electrons and therefore consists of 8 elements.The third period is similar to the second period – 8 elements.
23When you get to the fourth and fifth rows you have to include the transition metals. There are 10 transition metals in each of these rows.The total number of elements in the fourth and fifth rows are therefore 18 elements.
24When you get to the sixth and seventh rows you have to include the lanthanides and actinides. There are 14 elements in each of these groups.The total number of elements in the six and seventh rows can therefore include 32 elements.
26The period of an element can be determined from the element’s electron configuration. For example, arsenic – As, has the electron configuration of:[Ar]3d104s24p3The 4 in 4p3 indicates that arsenic is in the fourth period of the periodic table.
27Without looking at the periodic table give the period number for the following electron configuration:[Xe]6s2
28The s-Block ElementsThe elements of the s block are chemically reactive metals.The Group 1 metals are more reactive than the Group 2 metals.The outermost energy level in an atom of the Group 1 elements contain a single electron.The ease with which the single electron is lost make the Group 1 metals extremely reactive.
29Alkali Metals – The elements in Group 1 of the periodic table (lithium, sodium, potassium, rubidium, cesium and francium).Because the alkali metals are so reactive they are not found in nature as free elements.They combine vigorously with most nonmetals.They react strongly with water to produce hydrogen gas.
30Alkaline-Earth Metals – The elements in Group 2 of the periodic table (beryllium, magnesium, calcium, strontium, barium and radium).Atoms of the alkaline-earth metals contain a pair of electrons in their outermost shell.Slightly less reactive than the alkali metals.Still too reactive to be found in nature as free elements.
31ClassworkReview the practice problems 1 and 2a-d on page 133.
32The d-Block ElementsThe elements of the d block are known as the transition metals.They are good conductors of electricity and have a high luster.They are typically less reactive than the alkali and alkaline-earth metals.Palladium, platinum and gold are among the least reactive of all elements.
33ClassworkReview the practice problems 1 and 2a-b on page 136.
34The p-Block ElementsThe elements of the p-block and s-block are known as the main-group elements.The p-block consists of the elements in Groups (except helium).The properties of the p-block vary greatly.The p-block contains metals (Al), metalloids (Si) and nonmetals (Br).
35The electron configuration of bromine is: [Ar]3d104s24p5
36Halogens – the elements of Group 17 (fluorine, chlorine, bromine, iodine and astatine). The halogens are the most reactive nonmetals.They react vigorously with most metals to form compounds known as salts (NaCl).Fluorine and chlorine are gases. Bromine is a liquid and iodine is a solid.
37The Group 18 elements (Noble Gases) undergo few chemical reactions. This stability results from the gases electron configuration.Their highest occupied levels are completely filled with electrons (octet).An atom’s electron configuration governs the atom’s chemical properties.
38ClassworkReview the practice problems 1a-b and 2a-b on page 138.
39Homework Section Review – page 139 Questions 1, 2, 4 and 5 End of chapter problems – pageQuestions 27, 28 and 29Due:
41So far you have learned that the elements are arranged in the periodic table according to their atomic number.There is also a correlation between the arrangement of the elements and their electronic configuration.We will look at the relationship between the electron configurations and the periodic trends of the elements.
42Atomic RadiiIdeally, the size of an atom is defined by the edge of its orbital.However, this boundary varies under different conditions.One way to express the atomic radius is to measure the distance between the nuclei of two identical atoms that are bonded together, then divide this distance by two.
43Atomic radius may be defined as one-half the distance between the nuclei of identical atoms that are bonded together.
44Period TrendsThere is a gradual decrease across a row.
45There is a gradual decrease across a row. The trend to smaller atoms across a period is caused by increasing positive charge of the nucleus. Adding of protons or increasing atomic number.The electrons are pulled closer to the nucleus.The increase pull results in a smaller atomic radius.
47There is an increase down a group. As electrons are added to sublevels in higher energy levels located further from the nucleus, the size of the atoms increase.An exception is between aluminum (radius – 143 pm) and gallium (radius – 135 pm).This is due to the gallium being proceeded by the 10 d-block elements.The nuclear charge is considerably higher.
48ProblemOf the elements magnesium-Mg, chlorine-Cl, sodium-Na, and phosphorus-P, which has the largest atomic radius and why?Of the elements calcium-Ca, beryllium-Be, barium-Ba and strontium-Sr, which as the largest atomic radius and why?
49Ionization EnergyIonization energy (IE) – the energy required to remove one electron from a neutral atom of an element.A + energy A+ + e-An ion is an atom or group of bonded atoms that has a positive or negative charge.
52Period TrendsIn general, ionization energies of the elements increase across a period.Group 1 elements – have the lowest ionization energies. Therefore they lose electrons most easily. Very reactive.Group 18 elements - have the highest ionization energies . They do not lose electrons easily. Very low reactivity.
53The increase is due to increasing nuclear charge (more protons going across a period). A higher positive charge more strongly attracts electrons in the same energy level.Therefore, it is tougher to remove an electron from an atom.Increasing nuclear charge is responsible for both an increasing ionization energy and decreasing atomic radius across a period.
54Group Trends Ionization energies generally decrease down a group. Electrons removed from atoms of the elements down a group are farther from the nucleus.Also, the electrons from the lower energy levels shield the outer electrons.Therefore, they are removed more easily.
55Classwork Review practice problems 1and 2 on page 142. Review practice problems 1 (a-c) on page 146.
56Electron Affinity Neutral atoms can also acquire electrons. Electron Affinity – the energy change that occurs when an electron is acquired by a neutral atom.A + e A- + energyThe quantity of energy released is represented by a negative number.
58Period TrendsAmong the elements of each period, the halogens (Group 17) gain electrons most readily.The ease with which halogen atoms gain electrons is a major reason for the high reactivities of the Group 17 elements.As electrons add to the same p sublevel of atoms, electrons affinities increase.
59Period TrendsAn exception to this trend occurs between Group 14 and 15.Compare the electron affinities of carbon ([He] 2s2 2p2 ; ) and nitrogen[He] 2s2 2p3; 0).Adding an electron to nitrogen is more difficult because it forces the electron to pair with another electron.
60Group TrendsTrends for electron affinities within groups are not as regular as trends for ionization energies and atomic radii.
61Cations and Anions Cation (A+) – a positive ion that results with loss of an electron.Anion (A-) – a negative ion that results withthe gain of an electron.
62Valence ElectronsChemical compounds form because electrons are lost, gained or shared between atoms.The electrons that interact are those in the highest energy levels.Valence electrons – the electrons available to be lost, gained or shared in the formation of chemical compounds
63Valence electrons are often located in incompletely filled main-energy levels. For example, the electron lost in Na to form Na+ is from the 3s sublevel.For the main group elements, the valence electrons are the electrons in the outermost s and p sublevels.The inner electrons are in filled energy levels and are held to tightly to be involved.
65ElectronegativityElectronegativity is a measure of the ability of an atom in a chemical compound to attract electrons.In many compounds the negative charge of the valence electrons are not shared evenly between atoms.The uneven concentration of charge has an effect on the chemical properties of a compound.
67Period Trends Electronegativities tend to increase across a period. The Group 1 and 2 elements have the lowest electronegativities.Groups 16 and 17 have the highest electronegativities.
68Group Trends Electronegativities tend to decrease down a group. The combination of these trends in electronegativities results in the highest values belonging to the elements in the upper right of the periodic table (fluorine).
69ProblemOf the elements gallium-Ga, bromine-Br, and calcium-Ca, which has the highest electronegativities and why?
70Homework End of chapter problems – page 157-158 Questions 32, 34, 36 a-b, 37 and 46.Due: