Click a hyperlink to view the corresponding slides. Chapter Menu Section 8.1 Main Group Elements Section 8.2 Transition Elements Click a hyperlink to view the corresponding slides. Chapter Menu

Main Group Elements Relate the position of main group elements on the periodic table to their electron configurations. Predict the chemical behaviors of the main group elements. Relate chemical behavior to electron configuration and atomic size. Section 8.1

Main Group Elements inner transition element: one of the elements in the actinide or lanthanide series Section 8.1

Main Group Elements alkali metal alkaline earth metal halogen For the main group elements, both metallic character and atomic radius decrease from left to right across a period. Section 8.1

Patterns of Behavior of Main Group Elements Elements in the same group have similar properties because they have the same number of valence electrons. Elements in the same period have different properties because the number of valence electrons increases as you move from left to right in the row of the periodic table. Section 8.1

Patterns of Behavior of Main Group Elements (cont.) Section 8.1

Patterns of Behavior of Main Group Elements (cont.) Atomic radius is defined as one-half the distance between the nuclei of two identical atoms when those atoms are bonded together. With each increase in nuclear charge across the period, the outer electrons are attracted more strongly toward the nucleus, resulting in smaller atomic size. Section 8.1

Patterns of Behavior of Main Group Elements (cont.) As you move across a period on the periodic table from left to right, the size of atomic radii tend to decrease because the increasing positive charge of the nucleus holds the electrons tighter. As you move down a group on the periodic table from top to bottom, the size of atomic radii tend to increase because with each new period, a new energy level is added, making the radii larger. Section 8.1

Patterns of Behavior of Main Group Elements (cont.) Section 8.1

Patterns of Behavior of Main Group Elements (cont.) Section 8.1

Patterns of Behavior of Main Group Elements (cont.) Atomic size is an important factor in the chemical reactivity of an element. When atomic size is smaller, it is easier to keep electrons and attract extra electrons. When atomic size is larger, it is easier to lose electrons. Ionic size is also important in determining how ions behave in solution and the structure of solid ionic compounds. Section 8.1

Patterns of Behavior of Main Group Elements (cont.) Section 8.1

Patterns of Behavior of Main Group Elements (cont.) When an electron is lost, electrons that are not lost experience a greater attraction to the nucleus and pull together in a tighter bundle with a smaller radius. When an electron is added, the charge on the nucleus is not great enough to hold the increased number of electrons as closely as it holds the electrons in the neutral atom. Section 8.1

Patterns of Behavior of Main Group Elements (cont.) When an element becomes a positive ion, it loses electrons, and loses its outer energy level. As a result, positive ions tend to be smaller than their corresponding neutral atoms. When an element becomes a negative ion, it gains extra electrons, and the nucleus cannot hold the extra negative charge(s) as tightly. As a result, negative ions tend to be larger than their corresponding neutral atoms. Section 8.1

Patterns of Behavior of Main Group Elements (cont.) Section 8.1

Patterns of Behavior of Main Group Elements (cont.) Ionic radii decrease because nuclear charge increases. Section 8.1

Patterns of Behavior of Main Group Elements (cont.) In positive ions, electrons that are not lost experience a greater attraction to the nucleus and pull together in a tighter bundle with a smaller radius. In negative ions, when an electron is added, the charge on the nucleus is not great enough to hold the increased number of electrons as closely as it holds the electrons in the neutral atom. Section 8.1

Patterns of Behavior of Main Group Elements (cont.) Elements tend to react in ways that allow them to achieve the configuration of the nearest noble gas. Section 8.1

The Main Group Metals and Nonmetals Group 1 elements are called the alkali metals. Never found uncombined in nature. Lose their s valence electron and form a 1+ ion with the stable electron configuration of the noble gas in the preceding period. The most reactive alkali metal is the one that has the least attraction for the one valence electron (Francium) Section 8.1

The Main Group Metals and Nonmetals Group 1 elements: Most have a silvery color, are soft enough to cut with a knife, and have a low density. The reaction between alkali metals and water is violent, and produces hydroxides and hydrogen gas. 2Na (s) + 2H2O (l)  2NaOH (aq) + H2(g) Hydroxides are commonly found in industrial and household chemicals. Section 8.1

The Main Group Metals and Nonmetals (cont.) Group 2 elements are called the alkaline earth metals. They lose their s valence electrons and form a 2+ ion with the stable electron configuration of the noble gas in the preceding period. Group 2 elements are very reactive, but less reactive than group 1 elements because they lose 2 electrons. Group 2 elements are not found uncombined in nature. Section 8.1

The Main Group Metals and Nonmetals (cont.) Group 2 elements: Tend to be harder and denser than Group 1 elements, and have a higher melting point. Form hydroxides and hydrogen gas when reacting with water, but do not react with water as readily as Group 1 elements. Magnesium is present in the center of chlorophyll molecules, the pigments used in photosynthesis. Section 8.1

The Main Group Metals and Nonmetals (cont.) Group 13 elements tend to share electrons in covalent compounds rather than form ionic compounds Their valence configuration is s2p1, and they exhibit the 3+ oxidation number in most of their compounds. Good conductors of heat and electricity, but not as reactive as Groups 1 and 2. Section 8.1

The Main Group Metals and Nonmetals (cont.) Aluminum is the most abundant metallic element in Earth’s crust. Aluminum is used in soft-drink cans, antacids, and is often alloyed with other metals to form structural materials that are strong but light. Unlike the other group 13 elements, boron is a metalloid. Section 8.1

The Main Group Metals and Nonmetals (cont.) Group 14 elements usually share electrons rather than lose electrons to achieve a noble gas configuration Their valence configuration is s2p2, and they exhibit the 4+ oxidation number in most of their compounds. Group 14 is a mixed group, meaning it contains nonmetals, metalloids, and metals. Section 8.1

The Main Group Metals and Nonmetals (cont.) Group 15 elements form covalent bonds to achieve noble gas configuration Their valence configuration is s2p3. Mixed group Nitrogen is present in DNA and RNA. Section 8.1

The Main Group Metals and Nonmetals (cont.) Group 16 elements form covalent bonds to achieve noble gas configuration Their valence configuration is s2p4. Both metals and nonmetals react directly with molecular oxygen to form oxides. Sulfur is taken from underground deposits using the Frasch process. Section 8.1

The Main Group Metals and Nonmetals (cont.) Oxygen forms ionic compounds when combined with metals. Oxygen forms covalent compounds when combined with nonmetals. Section 8.1

The Main Group Metals and Nonmetals (cont.) Group 17 elements are called halogens. Active nonmetals that do not exist uncombined in nature When pure and in the gas state, are diatomic (F2, Cl2, Br2, I2) Their valence configuration is s2p5. Form –1 ion to form a noble gas configuration Section 8.1

The Main Group Metals and Nonmetals (cont.) Because the halogens react by gaining an electron, the most reactive element in the group is the one with strongest attraction for an electron (Fluorine) Section 8.1

The Main Group Metals and Nonmetals (cont.) Group 18 elements are the noble gases. no tendency to lose or gain electrons lack of reactivity form no naturally occurring compounds on Earth. Most were discovered by Sir William Ramsey, a Scottish chemist. Section 8.1

Section Assessment Atomic radius is defined as ___ the distance between the nuclei of two identical atoms when those atoms are bonded together. A. one-fourth B. one-half C. twice D. three-fourths Section 8.1

Section Assessment Elements in the same period have similar properties because they have the same number of valence electrons. A. true B. false Section 8.1

End of Section 8.1

Transition Elements Relate the chemical and physical properties of the transition elements to their electron configurations. Predict the chemical behavior of transition elements from their positions in the periodic table. Section 8.2

Transition Elements halogen: an element from group 17 (F, CI, Br, I, and At) that reacts with metals to form salts The properties of the transition elements result from electrons filling d orbitals; for the inner transition elements, electrons fill f orbitals. Section 8.2

Trends in Properties Each of the transition elements has its own properties that result from its atomic structure. With the exception of the group 12 elements, the transition metals have higher melting points and boiling points. Section 8.2

Trends in Properties (cont.) There is a wide range of oxidation numbers within the transition elements due to the involvement of the both the s and the d electrons in chemical bonding. The changes in atomic radii for the transition elements are not as great as the changes for the main group elements. Section 8.2

Other Transition Elements: A Variety of Uses Iron, cobalt, and nickel have nearly identical atomic radii, similar chemical properties, and are known as the iron triad. Section 8.2

Other Transition Elements: A Variety of Uses (cont.) The platinum group includes ruthenium, rhodium, palladium, osmium, iridium, and platinum. They are used as catalysts to speed up chemical reactions. Section 8.2

Other Transition Elements: A Variety of Uses (cont.) The coinage metals are copper, silver, and gold. They are malleable, relatively unreactive, and in the case of silver and gold, rare. Section 8.2

Other Transition Elements: A Variety of Uses (cont.) Chromium and zinc are corrosion-resistant metals that are often alloyed with other metals to protect them. Section 8.2

Other Transition Elements: A Variety of Uses (cont.) Section 8.2

Lanthanides and Actinides: The Inner Transition Elements The inner transition elements are found in the f block of the periodic table. In the lanthanides, electrons of highest energy are in the 4f sublevel. The only synthetic lanthanide is Promethium (Pm) which has the atomic number 61. Section 8.2

Lanthanides and Actinides: The Inner Transition Elements (cont.) In the actinides, electrons of highest energy are in the 5f sublevel. Cerium is the most abundant lanthanide and used to make the flints for lighters. The actinide uranium is a naturally occurring, radioactive element used as a source of nuclear fuel and other radioactive elements. Section 8.2

Lanthanides and Actinides: The Inner Transition Elements (cont.) All actinides are radioactive. Uranium is the largest naturally occuring element on the periodic table. All elements with atomic number larger than 92 are called trans-uranium elements, and all are synthetic. Plutonium is used in heart pacemakers, but is also the most toxic substance on Earth. Section 8.2

Section Assessment Which element is the most abundant lanthanide that is used to make flints for lighters? A. cerium B. uranium C. plutonium D. terbium Section 8.2

Section Assessment Which element is often used to prevent metals from corroding? A. nickel B. platinum C. chromium D. iron Section 8.2

Key Concepts In a period of the periodic table, the number of valence electrons increases as atomic number increases. From left to right across a period, atomic radius decreases. Down a group, atomic radius increases. The metal with the biggest atom and smallest number of valence electrons is the most active metal. The nonmetal with the smallest atom and greatest number of valence electrons is the most active nonmetal. Study Guide 1

Transition elements form the d block of the periodic table. Key Concepts Transition elements form the d block of the periodic table. Multiple oxidation states are characteristic of transition elements. Transition elements with similar atomic radii often have similar chemical properties. The iron triad, platinum group, and coinage metals are examples. The inner transition elements, the lanthanides and actinides, form the f block of the periodic table. Study Guide 2

Ionic radii decrease because the: A. nuclear charge increases B. nuclear charge decreases C. atomic size increases D. atoms are covalently bonded Chapter Assessment 1

Elements tend to react in ways that allow them to achieve the configuration of the nearest ___. A. nonmetal B. metalloid C. noble gas D. metal Chapter Assessment 2

Which is the least reactive of the alkali metals in group 1? A. cesium B. francium C. rubidium D. lithium Chapter Assessment 3

Which metal of group 13 is a metalloid? A. boron B. aluminum C. gallium D. thallium Chapter Assessment 4

Which is the most abundant element on Earth? A. hydrogen B. oxygen C. nitrogen D. aluminum Chapter Assessment 5

Which is the least reactive of the halogens? A. fluorine B. iodine C. selenium D. chlorine STP 1

Which elements are known as the iron triad? A. iron, cobalt, and nickel B. iron, ruthenium, and osmium C. iron, nickel, zinc D. manganese, iron, and nickel STP 2

Which group of elements is often used to speed up chemical reactions? A. noble gases B. iron triad C. platinum group D. coinage metals STP 3

Which actinide is a naturally occurring, radioactive element used as a source of nuclear fuel and other radioactive elements? A. platinum B. uranium C. cerium D. lithium STP 4

Which region in the periodic table are the most reactive metals located? A. s B. f C. p D. d STP 5

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