The Periodic Table

1. The Periodic Table A Summation of a Wealth of Information

2. SOL Objective • CH.2 The student will investigate and understand that the placement of elements on the Periodic Table is a function of their atomic structure. The periodic table is a tool used for the investigations of • Average atomic mass, mass number, and atomic number; • Isotopes, half lives, radioactive decay; • Mass and charge characteristics of subatomic particles;

3. SOL Objective (Continued) • Families or groups; • Series and periods; • Trends including atomic radii, electronegativity, shielding effect, and ionization energy; • Electron configurations, valence electrons, and oxidation numbers; • Chemical and physical properties; and • Historical and quantum models.

4. Major Understandings • The placement or location of an element on the Periodic Table gives an indication of the physical and chemical properties of that element. The elements on the Periodic Table are arranged in order of increasing atomic number. • The number of protons in an atom (atomic number) identifies the element. The sum of protons and neutrons in an atom (mass number) identifies an isotope. Common notations that represent isotopes 14C, Carbon – 14, or C – 14.

5. Major Understandings • Elements can be classified by their properties and located on the Periodic Table as metals, nonmetals, semi-metals (B, Si, Ge, As, Sb, Te), and inert gases. • Elements can be differentiated by physical properties. Physical properties of substances, such as density, conductivity, malleability (drawn into sheet), ductility (drawn into wire), solubility, and hardness, differ among elements. • Elements can also be differentiated by chemical properties. Chemicals properties describe how an element behaves during a chemical reaction.

6. Major Understanding (Continued) • The representative columns , Groups 1,2, and 13-18 on the Periodic Table, elements within the same number of valence electrons (helium is an exception) and therefore similar chemical properties. • The succession of elements within the same group demonstrates characteristics trends: differences in atomic radius, ionic radius, electronegativity. First ionization energy, metallic/nonmetallic properties.

7. Major Understandings (continued) • The succession of elements across the same period demonstrates characteristic trends: differences in atomic radius, ionic radius, electronegativity, first ionization energy, metallic/nonmetallic properties. • Some elements exist in two or more forms in the same phase. These forms differ in their molecular or crystal structure, and hence in their properties. These are called allotopes.

8. History of the Periodic Table • In 1869, Dmitri Mendeleev, a Russian Chemist, stated that the properties of the elements are periodic functions of their atomic masses. This means that the properties of elements repeat regularly and are related to the atomic masses of the elements. He based his conclusion on a study of the chemical properties observed in the elements then known. • This observations became the Periodic law.

9. Periodic Law • States that if the elements are arranged in order of increasing atomic mass, the physical and chemical properties repeat themselves regularly. • These repetitions are referred to as periodic functions, or as periodicity, which we now know these properties are periodic functions of atomic numbers.

10. The Modern Periodic Table • By 1900 the noble gas elements, He, Ne, Ar, Xe and Kr had been discovered and added to the table. • It was noticed that a few elements, when grouped by atomic mass, failed to appear in their proper places. • In 1913, Henry Moseley was able to determine the atomic number of each element. • When the periodic table was arranged by atomic number all the elements fell into place. • Thus the Periodic Law was revised.

11. Revised Periodic Law • It now states: The properties of the elements are periodic functions of their atomic numbers. • Which means, the elements are arranged in order of increasing atomic number, the properties of the elements repeat regularly.

12. Organization of the Periodic Table • The elements fall into horizontal rows and vertical columns. • The horizontal rows are called periods and are label 1,2,3,…. • The vertical columns are called groupsor families and are labeled with Roman numerals and letters such as IIA or IIB. • The main group known as the representative elementswere called the A group and the transition elements were called the B group.

13. International Union of Pure and Applied Chemistry (IUPAC) • IUPAC (I-yoo-pak) is an agency that governs many things in the scientific community. • Naming of elements • Finalizing the arrangement of the Periodic Table. • Establishing the rules for naming hydrocarbons and other organic compounds. • IUPAC changed the Roman Numeral version to columns consecutively numbered from 1-18. Modern chemist use both so some tables combine both versions.

14. Properties of Elements • Physical Properties • Chemical Properties • Atomic Radius • Covalent Radius • Ionic Radius • Electronegativity • Ionization Energy • Allotropes

15. Physical Properties • Physical properties of a substance are those characteristics that can be observed without the production of new substances. • Examples: color odor taste hardness density melting pt. boiling pt conductivity ductile malleable luster

16. Chemical Properties • Chemical Properties of a substance are those characteristics that describe how the substance interacts (or fails to interact) with other substances to produce new substances. • Examples • Combustiable • Flammable • Reactive or nonreactive

17. Atomic Radius • The Radius of an atom is the distance from the center of the nucleus to the outer shell. • As one proceeds from left to right in the period, the increase in nuclear charge – due to the increasing number of protons – pulls the electrons more tightly around the nucleus, thus reducing the atomic radius. • As one proceeds down a column the number of energy levels increase thus increasing the size of the atom.

18. Atomic Core • The core of the atom is sometimes called the kernel. • The Kernel contains the nucleus and the all the energy levels except the valence electrons. • In other words, it contains the nucleus and the filled energy levels. • As the kernel increases in size the shielding effect increases. • The shielding effect is where inner electrons block the attraction of the nucleus form outer electrons; therefore, the larger the radius of the atom the stronger the shielding effect.

19. Ionic Radius • A loss or gain of electrons by an atom causes a corresponding change in size. • Metal atoms lose one or more electrons when they form ions. Ionic radii of metals are smaller than the corresponding atomic radii. • Nonmetal atoms gain one or more electrons when they form ions. • Ionic radii of nonmetals are larger than the corresponding atomic radii. • Atomic and ionic radii are usually measured in Angstrom (A) units (1A = 1 x 10-10 meter)

20. Electronegativity • Electronegativity is a measure of the ability of an atom to attract the electrons that form a bond between it and another atom. • The values designated are based on an scale on which fluorine, the most electronegative, is assigned a value of 4.0. • The scale can be used to predict the type of intermolecular (attractive forces inside the molecule) bond formed.

21. ElectronegativityIonic or Covalent Character • The ionic or covalent character of a bond can be approximated from the differences in electronegativity between the atoms bonded. • If the difference is less than 1.7 it indicates that the bond is predominately covalent , with an exceptions. • If the difference is greater than 1.7 it indicates that the bond is predominately ionic.

22. Electronegativity Chart • HTTP://EN.WIKPEDIA.ORG/WIKI/ELECTONEGATIVITY#ELECTRONEGATIVITIES_OF_THE_ELEMENTS

23. Examples Using Differences • Na (0.9) and Cl (3.2) = 3.11, thus this an ionic bond. • C (2.6) and O (3.5) = 0.9, thus this is a covalent bond.

24. Ionization Energy • Ionization energy is the amount of energy required to remove the most loosely bound electron from an atom in the gaseous phase. • Measured in kJ/mole. • The energy required to remove the first electron is much lower than subsequent removals. • Elements can be classified on the basis of their first ionization energy.

25. Covalent Radius • A Covalent Radius is the effective distance from the center of the nucleus to the outer valence shell of that atom in a typical covalent or coordinate bond.

26. Ionization Potential Energy Chart • HTTP://EN.WIKPEDIA.ORG/WIKI/IMAGE:IONIZATION_ENERGIES.PNG

27. Allotropes • Allotropes are two or more forms of the same element that differ in their molecular or crystalline structure, and therefore in their properties. • Classical Example: Carbon • Graphite • Diamond • Fullerenes (buckyballs)

28. Classification of the Periodic Table • The Periodic Table is classified into three types of elements. • Metals • Semimetals • Nonmetals • General rule: Elements with three or fewer electrons in the outer level are considered to be metals. Elements with five or more electrons in the outer level are considered to be nonmetals. The exceptions are called semi metals.

29. Metals of the Periodic Table • More than 2/3 of the elements are metals. Metal atoms possess relatively low ionization energy (allowing them to lose electrons easily) and low electronegativity (allowing them to gain electrons easily). Metals tend to lose electrons and to form positive ions when combining with other elements.

30. Properties of Metals • Metallic properties are most pronounced in these elements on the lower left of the Periodic table. • Metals usually posses the properties of high thermal and electrical conductivity, metallic luster, malleability, and ductility. • With the exception of Hg all metals are solid at room temperature. • Alloys are mixtures of metals combined by heat or other means. This gives them improved characteristics such as stainless steel or bronze.

31. Nonmetals of the Periodic Table • Possess high ionization energies and have high electronegativity. • Most pronouned in the upper right corner, with the exception of the inert gases. • Tend to gain electrons when in combination with metals or to share electrons when in combination with other elements. • Most are gases with some solids ,except Br. • Tend to be brittle solids, have low thermal and electrical conductivity, and lack metallic luster.

32. Semimetals of the Periodic Table • Semimetals are those elements that have some properties characteristic of metals and other proterties characteristics of nonmetals. • They are used in the manufacture of semiconductors. • There are six of them B, Si, Ar, Te (Tellurium) , Ge , and Sb (Antimony). • They are solids.

33. Akali Metals • The Alkali metals are all the elements in Group 1 (IA) except Hydrogen. • Each element in this group has 1 valence electron, therefore, have an oxidation state of +1. • Displaces the H+ ion with ease. • Have relatively low ionization energy and electronegativity, therefore they form ionic compounds that are somewhat stable. • Alkali metals favor the halogens. (1+ + 1- = 0) • They are usually reduced to their free state by the electrolysis of their fused compounds.

34. Alkaline Earth Metals • The Alkaline metals are all the elements in Group 2 or (IIA). • Each element in this group has 2 valence electrons, therefore having an oxidation state of +2. • Not as reactive as Alkali metals. • Most are soluble in water. • Displaces the H+ ion with ease. • Have relatively low ionization energy and electronegativity, therefore they form ionic compounds that are somewhat stable.

35. Boron Family • The Boron family belongs to Group 13 or IIIA. • They have 3 valence electrons, therefore, all members have an oxidation state of +3 except Tl. • Boron is the only IIIA element that has nonmetallic properties and is classified as a semimetal. • Aluminum is the best known element of group IIIA • The rest of the elements are metals.

36. Carbon Family • Carbon Family is Group 14 or IVA. • The Carbon Group progresses from carbon (nonmetallic) to silicon and germanium (semimetals) to tin and lead (metals) • This group has 4 valence electrons, they have oxidation states of +2, +4, and -4.

37. Nitrogen Family • The Nitrogen Family is Group 15 or VA. • They have 5 valence electrons with an oxidation state of -3. • The elements in Group 15 show a marked progression from nonmetallic to metallic properties. • Nitrogen and phosphorus are typical nonmetals, arsenic is classified as a semimetal, and bismuth is metallic in both appearance and properties. • Nitrogen is relative inactive.

38. Oxygen Family (Chalcogens) • The Oxygen Family is Group 16 or VIA. • This family has 6 valence electrons with an oxidation state of -2. • The elements in Group 16 show a marked progression from nonmetallic to metallic properties . • Oxygen and sulfur are typical nonmetals, selenium and tellurium are classified as semimetals, and polonium show metallic properties. • Oxygen is an active nonmetal. • Selenium and tellurium are rare elements.

39. Halogen Group • This is Group 17 or VIIA. This elements have 7 valence electrons. • They are typical nonmetals, and have high ionization energies and high electronegativities. • Owing to their high reactivity, the halogens are found in nature only in compounds or as ions. • Fluorine has the highest electronegativity of any element and in compounds can show only a negative oxidation state. • Others in this group can show positive oxidation states.

40. Nobel Gases • Inert Gases are Group 18 or VIIIA and are monatomic gases. • They have complete outer shells; therefore they possess the highest ionization potential energies. • These elements are colorless, odorless, tasteless, and nonflammable under standard conditions. • Show very low chemical reactivity. • HTTP://EN.WIKPEDIA.ORG/WIKI/NOBLE_GAS

41. Transition Metals • Transition Metals are placed in between Group IIA and IIIA groups. • They are identified Roman Numerals and the alphabet B. http://en.wikipedia.org/wiki/Transition_metal • The Letters A and B change depending on which side of the Atlantic Ocean you are on.

42. Inner Transition Metals • The Inner Transition metals are divided into two series, Lanthanoids and Actinoids. • The term Rare Earths is used to describe Lanthanoids and Actinoids even though they are found abundant in nature. • The Inner transition metals exhibit different characteristics than the transition metal. • In 1945, Glenn T. Seaborg published his work and proposed the most significant change to Mendeleev’s Table.

43. The End • Study these notes well. I have condensed as much as possilbe.