The Periodic Table: Organizing Elements for Easy Reference

1. Chemistry Chapter 5 The Periodic Table

2. The Periodic Table of the Elements organizes essential information in a manageable format. • The modern periodic law states that the properties of elements vary with their atomic numbers in a periodic way. • The practice of grouping chemical elements into families with similar chemical properties was an important step in developing the concept of periodicity of the elements. The Periodic Table

3. In 1869, Russian chemist Dmitri Mendeleev published his version of a periodic table based on the elements’ atomic masses. When he noticed that there was a blank space indicating an element that was as yet unknown, Mendeleev reasoned this to be an element that was yet to be discovered. • Mendeleev’s periodic table was initially dismissed by the scientific community until 1875, when one of the missing elements (Gallium) was discovered. Dmitri Mendeleev

4. One problem was that even after most of Mendeleev’s “missing” elements were found, the table still had some problems. Arranging the elements in order of increasing atomic masses did not always produce a table that grouped similar elements. Problem

5. An Englishman named Henry Moseley, an assistant to Earnest Rutherford began researching the effects of x-rays on matter. He developed an experimental technique for counting the protons in an atom. • In 1912, he found that if he arranged the elements in the table according to atomic numbers, problems in the periodic table disappeared. Moseley’s work led to the modern periodic law, which states that the properties of elements vary with their atomic numbers in a periodic way. The Modern Periodic Law

6. The only major additions to the periodic table occurred after the second World War. Man discovered how to split the atom during WWII during the creation of the first atomic bomb, and with this, elements greater than atomic number 92 (uranium) were now possible to be produced. These elements are collectively called transuranium elements because they have atomic numbers greater than 92. Inasmuch as uranium is an unstable element, all of the transuranium elements are also unstable, and have very short half lives. So almost immediately after they are created, they decay down into a simpler, more stable atom. Artificial Elements

7. Each element has a cell. The following information is given in each cell for that particular element: • Atomic number: this appears at the top of the cell. • Name: This appears above its symbol • Symbol: The one-, two-, or three- letter symbol is the most prominent item in the cell. • Atomic mass: Located under the symbol is the weighted average atomic mass. The mass is given in atomic units (u). This number is given to four significant digits. If the atomic mass of an element is not known to that precision, the number is surrounded by parentheses. Structure of the Periodic Table

8. Electron configuration: The number and location of electrons in each occupied energy level in the neutral atom are listed below the atomic mass • Physical properties: colors and icons give information about the physical properties of the element, such as whether it is a metal or nonmetal and whether it is radioactive. Cont.

9. A vertical column is called a group or family because they have similar physical or chemical properties. • Horizontal rows are called periods or series. The period number on the left side of the table indicates the highest principal energy level (n) that electrons occupy in ground state atoms of that period. Cont.

10. The left side and the middle of the table (Groups 1-12) contain metals. Metals are usually solid, lustrous (shiny), malleable, and ductile, and they are good conductors of heat and electricity. • There are some exceptions such as mercury being a liquid. • The right side of the table contains the nonmetals. The heavy, stair-step line toward the right side of the table marks the boundary between the metals and the nonmetals. Nonmetals are in Groups 13-18 above the line. The nonmetals are generally gases or soft, crumbly solids. There are exceptions to these also, such as bromine, which is a liquid. Cont.

11. The metalloids are the elements immediately adjacent to the stair-step line. They share properties of both metals and nonmetals. Metalloids have metallic luster but tend to be crumbly, brittle solids. They can conduct electricity better than nonmetals but not as well as metals. • Two rows, called the lanthanide series elements and the actinide series are place at the bottom of the table. These are f block elements where interior f sublevel electrons are added with increasing atomic number the Lanthanide series fits into the table immediately after Lanthanum, and the actinide series fits into the table after actinium. If those elements were in their proper places within the periodic table, the table would be expanded into an oversized, unmanageable shape. Cont.

12. The distance from the center of the atom’s nucleus to it’s outermost electron is its atomic radius. • In general, the radii of atoms decrease in size as you move from left to right across a period of the periodic table. • Thus, as the atomic number increases in a period, the outer shell electrons are held progressively more tightly, and the average distance from the nucleus to the outer-shell electrons decreases. Atomic Radii

13. The minimum energy required to remove the first electron from its outermost shell to make it a cation is called its first ionization energy. • Some atoms lose their electrons easily, while others stubbornly hold on to theirs, depending upon their ionization energy. • Ionization energies generally increase from left to right across a period because the strength with which protons in the nucleus attract the outer-shell electrons increases. It thus becomes more difficult to remove an electron closer to and more strongly attracted to an increasingly positive nucleus. Ionization Energy

14. Electron affinity is the amount of energy required to add an electron to a neutral atom to form a negative ion, or anion. Electron affinity is the opposite of ionization energy. • Electron affinity measures how strongly an atom attracts additional electrons. This property is most affected by the fullness of an atom’s highest energy sublevel. For incomplete sublevels, most elements will easily accommodate the additional electron, releasing energy. • In general, electron affinity energies become larger from left to right along a period. • As an energy level continues to fill, it has a stronger attraction for the electrons. Electron Affinity

15. The measure of attraction between the nucleus and valence electrons is called electronegativity. • In most cases, electronegativity is determined for atoms bonded in molecules which share electrons with other atoms. Thus, electronegativity is really a measure of an atom’s ability to attract and hold electrons in a molecule. • In elements toward the right end of a period, the relatively stronger nuclear charge pull the outer-shell electrons closer to the nucleus and decreases the size of the atom. Thus, it makes the removal of electrons more difficult and encouraged the addition of electrons. Electronegativity

16. Group 1 (1A) elements are metal that are very chemically reactive. • They are called the alkali metals. • Physical Properties: Good conductors of heat and electricity, and have a bright metallic luster. • Low density, some less dense than water, and very soft at room temperature. Group 1: The Alkali Metal Family

17. Chemical Properties: • A solitary , loosely held electron in the outermost energy level makes this family of elements very reactive. • Alkali metals donate their electrons readily to attain the same stable electron configuration as the noble gases. Group 1 (Cont.)

18. Group 2 (2A) • These metals are all solid at room temperature and have typical metallic properties. They are denser, harder, and have higher melting points than the alkali metals. They usually form cations with a +2 charge, losing two electrons in order to have the same electron configuration as noble gases. • Listed by increasing atomic number, the alkaline-earth metals of Group 2 are beryllium, magnesium, calcium, strontium, barium, and radium. Group 2-The Alkaline-Earth Metal Family

19. Physical Properties: In pure samples of the alkaline-earth metals, freshly cut surfaces range from bright silvery to white in appearance. The metals quickly oxidize to a dull gray or yellow color. Densities are slightly higher than those of the alkali metals, but these metals are much harder. All the alkaline-earth metals are malleable. • Chemical properties: Each neutral alkaline-earth metal atom has two electrons in its outermost 2 sublevel. The alkaline-earth metals typically donate the two electrons when they combine with nonmetal elements. The elements toward the bottom of the group are the most reactive because the electrons are the most loosely held. Group 2 (Cont.)

20. All of the d block groups on the periodic table belong to the group of elements called transition metals. • Physical properties: Transitional metals exhibit the qualities typical of metals. Unlike the first two metal families, most of these metals have high densities, , are reasonably hard, and gave considerable toughness or strength. They typically have a shiny luster on freshly cut surfaces, conduct heat and electricity well, and are more or less ductile and malleable. Group 3-12 The Transition Metals

21. Chemical properties: Because their highest energy electrons occupy interior d sublevels, transition metals generally have similar chemical properties. However, there are also many exceptions, which are caused by the specific quantum mechanical relationships between the electron structure and nuclear charges. Cont.

22. Lanthanide and actinide series of elements are usually displayed below the main periodic table in two row of fourteen cells. These are called series rather than periods because they actually fit into the sixth and seventh periods between the s block and d block elements for those periods, respectively. These two series are called the inner transition metals. The Inner Transition Metals

23. Physical properties: The majority of the lanthanide series is strongly paramagnetic. Paramagnetism is a property of materials that are weakly attracted by a magnetic field because of unpaired electrons. All the elements in the lanthanide series occur naturally except promethium. Cont.

24. Chemical properties: The highest energy electrons of the inner transition metals occupy the 4f and 5f sublevels. Although the atoms of the elements lanthanum and actinium contain no 4f and 5f sublevels. Although the atoms of the elements lanthanum and actinium contain no 4f or 5f electrons themselves, their outer electron structures resemble those of the lanthanide and actinide elements closely. Cont.

25. As their name implies, these follow the transition metals on the periodic table. They include Groups 13-16 (3A-6A). This group of metals contains well-known elements such as aluminum, tin, and lead, as well as obscure elements such as thallium, indium, and gallium. Groups 13-16: The Post-Transition Metals and the Metalloids

26. These congregate around the stair-step line between the cells in Groups 13-17. Their characteristic-luster, hardness, conductivity, and chemical reactivity lies somewhere between those of the metals and of the nonmetals. Boron, silicon, arsenic, antimony, and tellurium are included in the metalloid family. • They can conduct electricity, but only under certain conditions. Consequently, they are called semiconductors. Mellaloids

27. Group 13 consists solely of post transition metals and a metalloid. There are significant differences between the chemical properties of boron, a metalloid, at the top of the column and the five metals below. These five metals are aluminum, gallium indium, thallium and ununtrium. Boron has some metalloid properties, but the characteristics we associate with metalloids are more recognizable in other groups. Group 13: The Boron Filmily

28. The two most economically important elements of Group 13 are boron and aluminum. Boron can transmit portions of the infrared spectrum and it conducts electricity well only at high temperatures. • Aluminum, on the other hand, is a very important metal because it combines high strength and low density, especially in its alloys. Unlike the metalloid boron, aluminum displays a silvery metallic luster, is easily machined, and is highly conductive. Aluminum is the most common metal in the earth’s crust, found mostly in clays. Physical Properties

29. Boron’s small size allows the nucleus to hold electrons as though the nucleus has a greater positive charge than it actually does. • Aluminum is too chemically reactive to be found as a native mineral. It is usually bonded to oxygen atoms in aluminum ores, the most common of which is called bauxite. Like iron, aluminum corrodes in the presence of atmospheric oxygen. Chemical Properties

30. Carbon is more important than all the other elements in its family. • Carbon compounds are the basis for life. So many biological carbon-based compounds are known that an entire area of chemistry, called biochemistry, is devoted to their study. • Also, there are literally millions of other carbon compounds that are studied in another area of chemistry called organic chemistry. Group 14: The Carbon Family

31. Elements in the carbon family are all solids at room temperature. Carbon itself takes several forms. It can occur as an amorphous solid that is very soft and dull black in color. As graphite, it is soft, black solid that feels slippery because it is made of sheet of carbon atoms that slide easily across each other. As diamond, carbon is a clear-to- slightly colored, extremely hard, crystalline solid. Physical Properties

32. All members of the carbon family have four valence electrons. However, the distance and strength of attraction of the valence shell electrons and the nucleus seem to determine the basic chemical properties of these elements. Carbon shares its four valence electrons, and depending on the kind of atom it combines with, may form single, double, or even triple bonds. Carbon generally has low chemical reactivity, but it combusts readily in oxygen to form carbon dioxide or carbon monoxide. Chemical Properties

33. This group exhibits a dramatic range of properties from top to bottom • First is the element nitrogen, a gas, followed by four solids: Phosphorus, arsenic, antimony, and bismuth are metalloids, and bismuth is a post-transition metal. • Neutral forms of these elements have five valence electrons, but they have an unusual ability to transfer or acquire electrons, but they have an unusual ability to transfer or acquire electron as needed when combining with other elements. Group 15: The Nitrogen Family

34. Nitrogen normally exists as diatomic N2 molecules in the gaseous state. It has no taste, no color, and no odor, and it accounts for approximately 78% of the volume of the earth’s atmosphere. Physical Properties

35. Nitrogen as an element gas is essentially inert. The atoms in these molecules are tightly bonded together and are difficult to split up. Only under relatively high temperatures can the element be forced to combine with other elements. Chemical Properties

36. The oxygen family includes several reactive and important elements. Oxygen is the most easily recognized nonmetal element in this group, although sulfur and selenium are also nonmetals. Tellurium is a highly reactive metalloid with few industrial uses. Polonium is believed to be a reactive pot transition metal. Group 16: The Oxygen Family

37. Oxygen, which is a colorless, odorless , tasteless gas, forms about 21% of the earth’s atmosphere. It is slightly soluble in water and is the most abundant element by mass in the earth’s crust. Through God’s design, enough oxygen dissolves in lakes, rivers, and oceans to sustain fish and aquatic plants. Atmospheric oxygen exists in two forms: gas (O2) and ozone (O3). Lightning can convert odorless oxygen into pungent ozone, which we can often smell after an electrical storm. Physical Properties

38. The halogen family is probably the most chemically uniform group of elements other than the noble gases. These elements are called halogen because they form salts when they react with reactive metals. They are so reactive that they are difficult to obtain and keep in their elemental forms. In order of increasing mass, the halogens are fluorine, chlorine, bromine, iodine, and astatine. With the exception of astitine, the halogens are nonmetals. Group 17: The Halogen Family

39. Halogens sow a definite trend in their physical properties. As their atomic number increase, their densities, melting points, and boiling points increase, and their colors exhibit increasingly darker hues. Physical Properties

40. Group 18 are called noble gases because they do not react with other elements except under condition of pressure and temperature. Group 18: The Noble Gases

41. All noble gases are colorless, odorless, and tasteless. Extremely low boiling point points and freezing points indicate that the individual atoms of these gases have little attraction for each other. Physical Properties

42. The End!