Chapter 6 The Periodic Table and Periodic Law

Development of the Modern Periodic Table Section 6.1 Development of the Modern Periodic Table

Objectives Trace the development and Identify key features of the periodic table.

History 1790s, French scientist Lavoisier 23 elements 1800s: electricity and spectrometer

John Newlands Patterns of the periodic table Law of octaves Elements on the eights had similarities

Meyer & Mendeleev 1869-Meyer and Mendeleev: connection between atomic mass and properties Mendeleev published it first Left holes of undiscovered elements Predicted properties of undiscovered elements- Sc, Ga, Ge

Moseley Problems with Mendeleev Rows by increasing atomic mass Moseley used atomic number instead

The Periodic Law There is a periodic repetition of chemical and physical properties of the element when they are arranged by increasing atomic number.

The Modern Periodic Table Horizontal rows- periods Vertical columns- groups or families

Groups 1A through 8A = Representative Elements Wide range of chemical and physical properties Groups 1B through 8B = Transition Elements

Metals shiny, smooth solid room temperature good conductors of heat and electricity

Alkali Metals Alkali Metals= 1A (excluding hydrogen) highly reactive

Alkaline Earth Metals Alkaline Earth Metals= 2A highly reactive (not as much as 1A)

Transitions Transition metals Inner transition metals Group B elements contained in the D block of the table Inner transition metals the lanthanide and actinide series F block

Nonmetals Halogens=7A Noble Gases= 8A Generally a gas or a brittle, dull-looking solids Poor conductors Halogens=7A REALLY REACTIVE Noble Gases= 8A unreactive and stable (all valence electrons are filled)

Metalloids contain the physical and chemical properties of both metals and nonmetal

Homework Section 6.1 Assessment 1-6 on page 158

Reactivity Trends Increases down the table for the metals Decreases down the table for the nonmetals                                                                                                                                         

Classification of the Elements Section 6.2 Classification of the Elements

Objectives Explain why elements in the same group have similar properties Identify the four blocks of the periodic table based on electron configuration

Valance Electrons The properties of each element in each group are similar because they have the same number of valence electrons

Valence Electrons and Period Number Energy level of valence electrons = period on the table Example: Lithium: period 2, valence electron in 2nd energy level (1s22s1)

Valence Electrons and Group Number Group number (1A-8A) = number of valence electrons

Putting it Together Oxygen is in the 3rd period and in group 6A. Oxygen’s valence electrons are located in the ____ energy level. Oxygen has ___ valence electrons.

S,P,D, and F Blocks 4 different energy sublevels: s, p, d, and f S block= 1A and 2A holds max of 2 electrons P block= 3A through 8A max holds 6 electrons S block must fill before P block can fill Noble gases are stable because of filled S and P blocks

S,P,D, and F Blocks Continued… D block = transition metals max of 10 electron F block= inner transition metals unpredictable manner of filling max of 14 electrons

Reactivity Trends Increases down the table for the metals Decreases down the table for the nonmetals                                                                                                                                         

Homework Page 162, #10-15

Periodic Trends: Atomic Radius For metals, atomic radius = ½ distance between adjacent nuclei in a crystal element For nonmetals, atomic radius = ½ distance between nuclei of identical atoms that are chemically bonded

Periodic Trends: Atomic Radius DECREASES I N C R E A S

Atomic Radius The increase from top to bottom is due to adding electron shells. The decrease from left to right is due to increased nuclear charge as you move to the right, which draws electrons closer to the nucleus.

Periodic Trends: Ionization Energy Ionization energy= energy required to remove an electron from a gaseous atom Octet rule = atoms tend to gain lose or share electrons to acquire a full set of 8 valence electrons

Periodic Trends: Ionization Energy INCREASES D E C R A S

Periodic Trends: Electronegativity Electronegativity= relative ability of an atom to attract electrons in a chemical bond.

Electronegativity Arbitrary units called Paulings (after Linus Pauling) are used to express electronegativity. Electronegativity increases from left to right across a period and from top to bottom down a group.

Periodic Trends: Electronegativity INCREASES D E C R A S