The Periodic Law Similar physical and chemical properties recur periodically when the elements are listed in order of increasing atomic number.

Transcription

1 The Periodic Law Similar physical and chemical properties recur periodically when the elements are listed in order of increasing atomic number. Each period ends with a completely filled outer shell that has the maximum number of electrons for that shell. The number identifying the A families identifies the number of electrons in the outer shell, except helium. The outer shell electrons are responsible for chemical reactions. Group A elements are called representative elements. Group B elements are called transition elements.

2 ns 1 Ground State Electron Configurations of the Elements d 1 ns 2 ns 2 np 1 ns 2 np 2 ns 2 np 3 ns 2 np 4 ns 2 np 5 ns 2 np 6 d 5 d 10 4f 5f

3 The horizontal rows of the periodic table are called PERIODS.

4 The elements in any group of the periodic table have similar physical and chemical properties! The vertical columns of the periodic table are called GROUPS, or FAMILIES.

5 Alkali Metals

6 Alkaline Earth Metals

7 Transition Metals

8 These elements are also called the rare-earth elements. InnerTransition Metals

9 Halogens

10 Noble Gases The Inert (Noble) Gases The six noble gases, He, Ne, Ar, Kr, Xe, and Rn, rarely enter into chemical reactionsall have complete octets... = stability!

11 Periodic Relationships The valence shell is the outermost occupied shell The period number = principal quantum number, n, of the electrons in the valence shell

12 Periodic Relationships For main group elements the number of valence shell electrons is the same as the periodic table A group number

13 Families Periods Columns of elements are called groups or families. Elements in each family have similar but not identical properties. For example, lithium (Li), sodium (Na), potassium (K), and other members of family IA are all soft, white, shiny metals. All elements in a family have the same number of valence electrons. Each horizontal row of elements is called a period. The elements in a period are not alike in properties. In fact, the properties change greatly across even given row. The first element in a period is always an extremely active solid. The last element in a period, is always an inactive gas.

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15 Metals, Nonmetals, and Metalloids Metals have a small number of electrons in their valence shells and tend to form positive ions Except for hydrogen and helium, all s-block elements are metals All d- and f-block elements are metals

16 Metals, Nonmetals, and Metalloids Atoms of a nonmetal generally have larger numbers of electrons in their valence shell than do metals, and many tend to form negative ions Nonmetals are all p- block elements and include hydrogen and helium Metalloids have properties of both metals and nonmetals

17 Metal: Elements that are usually solids at room temperature. Most elements are metals. Non-Metal: Elements in the upper right corner of the periodic Table. Their chemical and physical properties are different from metals. Metalloid: Elements that lie on a diagonal line between the Metals and non-metals. Their chemical and physical properties are intermediate between the two.

18 Properties of Metals Metals are good conductors of heat and electricity. Metals are shiny. Metals are ductile (can be stretched into thin wires). Metals are malleable (can be pounded into thin sheets). A chemical property of metal is its reaction with water which results in corrosion.

19 Properties of Non-Metals Non-metals are poor conductors of heat and electricity. Non-metals are not ductile or malleable. Solid non-metals are brittle and break easily. They are dull. Many non-metals are gases. Sulfur

20 Properties of Metalloids Metalloids (metal-like) have properties of both metals and non-metals. They are solids that can be shiny or dull. They conduct heat and electricity better than nonmetals but not as well as metals. They are ductile and malleable. Silicon

21 Atomic Mass Atomic Number Symbol Charge (if ion)

22 Atomic Number, Z All atoms of the same element have the same number of protons in the nucleus, Z 13 Al Atomic number Atom symbol AVERAGE Atomic Mass

23 Mass Number, A C atom with 6 protons and 6 neutrons is the mass standard = 12 atomic mass units Mass Number (A) = # protons + # neutrons NOT on the periodic table (it is the AVERAGE atomic mass on the table) A boron atom can have A = 5 p + 5 n = 10 amu A Z 10 5 B

24 Isotopes Atoms of the same element (same Z) but different mass number (A). Boron-10 ( 10 B) has 5 p and 5 n Boron-11 ( 11 B) has 5 p and 6 n 11 B 10 B

25 IONS IONS are atoms or groups of atoms with a positive or negative charge. Taking away an electron from an atom gives a CATION with a positive charge Adding an electron to an atom gives an ANION with a negative charge.

26 Hydrogen 1 1 H Protons: 1 Neutrons: 0 Electrons: 1

27 Sodium Protons: 11 Neutrons: 12 Na Electrons: 11

28 Rhenium Re Protons: 75 Neutrons: 111 Electrons: 75

29 Rhenium isotope Re Protons: 75 Neutrons: 112 Electrons: 75

30 EXAMPLE How many protons, neutrons and electrons are found in an atom of Cs Atomic number = protons and electrons There are 55 protons and 55 electrons Mass number = sum of protons and neutrons = 78 There are 78 neutrons

31 Describe how to read the periodic Every table has: table:

32 Describe how to read the periodic table: Atomic Number The number of protons in an atom identifies the element. The number of protons in an atom is referred to as the atomic number of that element. Atomic Symbol: The atomic symbol is one or two letters chosen to represent an element ("H" for "hydrogen," etc.). These symbols are used every where in the world Usually, a symbol is the abbreviation of the element or the abbreviated Latin name of the element. Atomic Mass: The atomic mass is the average mass of an element in atomic mass units ("amu"). Though individual atoms always have a whole number of amus, the atomic mass on the periodic table is shown as a decimal number because it is an average of all the isotopes of an element.

33 Sub-Levels We can deduce the general form of electron configurations directly from the periodic table

34 Electron Configurations and the Periodic Table The periodic table can be used as a guide for electron configurations. The period number is the value of n. Groups 1A and 2A have the s-orbital filled. Groups 3A - 8A have the p-orbital filled. Groups 3B - 2B have the d-orbital filled. The lanthanides and actinides have the f- orbital filled.