# The Periodic Table Chapter 6. Why is the Periodic Table important to me? The periodic table is the most useful tool to a chemist. You get to use it on.

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The Periodic Table Chapter 6

Why is the Periodic Table important to me? The periodic table is the most useful tool to a chemist. You get to use it on every test. It organizes lots of information about all the known elements.

Pre-Periodic Table Chemistry … …was a mess!!! No organization of elements. Imagine going to a grocery store with no organization!! Difficult to find information. Chemistry didn’t make sense.

Dmitri Mendeleev: Father of the Table HOW HIS WORKED… Put elements in rows by increasing atomic weight. Put elements in columns by the way they reacted. SOME PROBLEMS… He left blank spaces for what he said were undiscovered elements. (Turned out he was right!) He broke the pattern of increasing atomic weight to keep similar reacting elements together.

The Current Periodic Table Mendeleev wasn’t too far off. Now the elements are put in rows by increasing ATOMIC NUMBER!! The horizontal rows are called periods and are labeled from 1 to 7. The vertical columns are called groups are labeled from 1 to 18. Atomic structure is used to organize the elements in the periodic table. The periodic table is useful in predicting the chemical behavior, trends, and the properties of the elements.

Atomic Structure Review Atoms are made of protons, electrons, and neutrons. Elements are atoms of only one type. Elements are identified by the atomic number (# of protons in nucleus).

Energy Levels Review Electrons are arranged in regions around the nucleus called energy levels. At least 1 energy level and as many as 7 levels exist in atoms. Electrons in levels farther away from the nucleus have more energy. Inner levels will fill first before outer levels.

Energy Levels & Valence Electrons Energy levels hold a specific amount of electrons: –1 st level = up to 2, –2 nd level = up to 8 –3 rd level = up to18 The electrons in the outermost level are called valence electrons. –Determine how elements will react with others –Outermost level does not usually fill completely with electrons.

Using the Table to Identify Valence Electrons Elements are grouped because they have similar properties. Group numbers can help you determine the number of valence electrons: –Group 1 has 1 valence electron. –Group 2 has 2 valence electrons. –Groups 3 – 12 are transition metals and have 1 or 2 valence electrons.

Using the Table to Identify Valence Electrons cont. Groups 13 – 18 have 10 fewer than the group number. For example: –group 13 has 3 valence electrons –group 15 has 5 valence electrons –group 18 has 8 valence electrons

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.

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.

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 non-metals but not as well as metals. They are ductile and malleable.

Groups…Here’s Where the Periodic Table Gets Useful!! Elements in the same group have similar chemical and physical properties!! (Mendeleev did that on purpose.) Why?? They have the same number of valence electrons. They will form the same kinds of ions.

Grouping the Elements The most reactive metals are the elements in Group 1 and 2. What makes an element reactive? ● Number of valence electrons each atom has ● When outer levels are full, atoms are stable ● When they are not full, they react: gain, lose, or share 1 or 2 electrons

Groups Groups run vertically in the periodic table. They are numbered from 1 – 18. Elements in the same groups have the same number of electrons in the outer energy level. Grouped elements behave chemically in similar ways.

Families on the Periodic Table Columns are also grouped into families. Families may be one column, or several columns put together. Families have names rather than numbers. (Just like your family has a common last name.)

Hydrogen Hydrogen belongs to a family of its own. Hydrogen is a diatomic, reactive gas. Hydrogen was involved in the explosion of the Hindenberg. Hydrogen is promising as an alternative fuel source for automobiles

Alkali Metals 1 st column on the periodic table (Group 1) not including hydrogen. Very reactive metals, react violently with water Always combined with something else in nature (like in salt). Soft enough to cut with a butter knife Valence Electrons: 1 Shiny solids

Alkaline Earth Metals Second column on the periodic table. (Group 2) Reactive metals that are always combined with nonmetals in nature. Several of these elements are important mineral nutrients (such as Mg and Ca) Valence Electrons: 2 Solids Silver colored More dense than alkali metals

Transition Metals Elements in groups 3-12 Less reactive harder metals Includes metals used in jewelry and construction. Metals used “as metal.” Valence Electrons: 1 or 2 Higher density Good conductors of heat and electricity

Groups 3-12 Transition Metals Below Main Table Contain: The Lanthanide and Actinide Series –These two rows are pulled out of sequence and placed below the main table to keep the table from being too wide. –Lanthanides are #’s 58 – 71. –Actinides are #’s 90 – 103.

Groups 3-12 Rare Earth Elements ~ Lanthanides Lanthanides follow the transition metal # 57 Lanthanum in Period 6. Valence electrons: 3 Reactivity: Very reactive Properties: ● High luster but tarnish easily ● High conductivity for electricity ● Very small differences between them

Groups 3-12 Rare Earth Elements ~ Actinides Actinides follow the transition metal # 89 Actinium in Period 7 Valence electrons: 3 (but up to 6) Reactivity: unstable –All are radioactive –Most made in laboratories

Boron Family Elements in group 13 Contains 1 metalloid and 4 metals Valence Electrons: 3 Somewhat reactive Solids at room temperature Aluminum metal was once rare and expensive, not a “disposable metal.”

Carbon Family Elements in group 14 Contains: 1 non-metal, 2 metalloids, and 3 metals Valence Electrons: 4 Varied reactivity Contains elements important to life and computers. Carbon is the basis for an entire branch of chemistry. Silicon and Germanium are important semiconductors. Solids at room temperature

Nitrogen Family Elements in group 15 Nitrogen makes up over ¾ of the atmosphere. Nitrogen and phosphorus are both important in living things. Most of the world’s nitrogen is not available to living things. The red stuff on the tip of matches is phosphorus. Contains: 2 non-metals, 2 metalloids, and 1 metal Valence Electrons: 5 Varied reactivity All but Nitrogen solids at room temperature

Elements in group 16 Oxygen is necessary for respiration. Many things that stink, contain sulfur (rotten eggs, garlic, skunks, etc.) Contains: 3 non-metals, 1 metalloid, and 2 metals Oxygen Family or Chalcogens Valence Electrons: 6 Somewhat reactive All but Oxygen are solids at room temperature

Halogens Elements in group 17 Very reactive, volatile, diatomic, nonmetals Always found combined with other element in nature. Used as disinfectants and to strengthen teeth. Contain: non-metals Valence Electrons: 7 Very reactive Poor conductors of electric current React violently with alkali metals to form salts

The Noble Gases

Elements in group 18 VERY unreactive, least reactive group Used in lighted “neon” signs Used in blimps to fix the Hindenberg problem. Outermost energy level full Contains: non-metals Valence Electrons: 8 (2 for He) Colorless, odorless gases at room temperature All found in atmosphere

Periods Periods run horizontally across the Periodic Table Periods are numbered 1 – 7 All the elements in a period will have the same number of energy levels, which contain electrons. Examples: »Period 1 atoms have 1 energy level. »Period 2 atoms have 2 energy levels. »Period 5 atoms have 5 energy levels.

Periods continued Moving across from left to right across a period, each element has one more electron in the outer shell of its atom than the element before it. This leads to a fairly regular pattern of change in the chemical behavior of the elements across a period.

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