Periodic Table A Closer Look

History of the Periodic Table Mendeleev arranged the elements into the world’s 1 st periodic table Mendeleev arranged the elements into the world’s 1 st periodic table Increasing atomic mass Increasing atomic mass Atomic mass was known by comparing the amounts of elements that reacted with each other Atomic mass was known by comparing the amounts of elements that reacted with each other

Modern Periodic Table Not identical to Mendeleev’s table – he didn’t know about protons and electrons Not identical to Mendeleev’s table – he didn’t know about protons and electrons Increasing atomic number instead of mass Increasing atomic number instead of mass Number of protons Number of protons Number of electrons Number of electrons

Groups Columns on the table Columns on the table Same number of valence electrons Same number of valence electrons Similar chemical properties Similar chemical properties Similar physical properties Similar physical properties More reactive as you go down in a group More reactive as you go down in a group Group 1 – Alkali metals Stored in oil so they won’t react with the air

Valence Electrons Outermost electrons Outermost electrons They participate in all chemical bonds They participate in all chemical bonds Every atom “wants” eight valence electrons Every atom “wants” eight valence electrons Noble gases already have eight valence electrons – least reactive elements Noble gases already have eight valence electrons – least reactive elements

Groups Numbered left to right Numbered left to right Group 1 – alkali metals Group 1 – alkali metals Group 2 – alkaline earth metals Group 2 – alkaline earth metals Groups 3 to 12 – transition metals Groups 3 to 12 – transition metals Groups 13 to 16 – metals, metalloids, & nonmetals Groups 13 to 16 – metals, metalloids, & nonmetals Group 17 – halogens Group 17 – halogens Group 18 – noble gases Group 18 – noble gases

Group 3 Scandium Scandium Yttrium Yttrium Lanthanum Lanthanum Actinium Actinium

Periods Horizontal rows Horizontal rows The two at the bottom are part of rows 6 & 7 The two at the bottom are part of rows 6 & 7 Same number of energy levels Same number of energy levels Properties change in the same way across each row (periodic law) Properties change in the same way across each row (periodic law)

Period 3 Lithium Lithium Beryllium Beryllium Boron Boron Carbon Carbon Nitrogen Nitrogen Oxygen Oxygen Fluorine Fluorine Neon Neon

General Categories Metals Metals Shiny Shiny Conductors Conductors Ductile Ductile Malleable Malleable Nonmetals Nonmetals Dull Dull Insultators Insultators Brittle Brittle Metalloids Metalloids Properties of both Properties of both

Placement on the Periodic Table Metals Metalloids Nonmetals

Period 4, Group 1 contains K, which is potassium

Properties of Metals Shiny Shiny Conductors Conductors Ductile Ductile Malleable Malleable

Metallic Elements Metallic properties increase as you move down and to the left Metallic properties increase as you move down and to the left Most metallic elements are in group 1 Most metallic elements are in group 1

Alkali Metals Group 1 Group 1 Li Li Na Na K Rb Rb Cs Cs Fr Fr Very reactive Very reactive Easily lose one valence electron The further out the electron is from the nucleus the easier it is to lose it Reactivity increases as you go down in the group Reactivity increases as you go down in the group

Alkaline Earth Metals Group 2 Group 2 Be Be Mg Mg Ca Ca Sr Sr Ba Ba Ra Ra

Properties of Alkaline Earth Metals Less reactive than alkali metals Less reactive than alkali metals Don’t reactive as violently with water Don’t reactive as violently with water Need more energy to begin their reactions Need more energy to begin their reactions Lose two valence electrons Lose two valence electrons

Transition Metals Groups 3 to 12 Groups 3 to 12 AKA “heavy metals” AKA “heavy metals” Large nuclei Large nuclei Form colored compounds Form colored compounds

Alloys Homogeneous mixture of metals Homogeneous mixture of metals Mix together metals to get the exact properties you want Mix together metals to get the exact properties you want Instruments, jewelry, construction, etc. Instruments, jewelry, construction, etc. Sterling silver, brass, bronze, steel Sterling silver, brass, bronze, steel

Coinage Metals Resistant to corrosion Resistant to corrosion Expensive Expensive Found in pure form Found in pure form Three – Three – Copper Copper Silver Silver Gold Gold

Rare Earth Metals

Long Periodic Table This is too long for practical use, so we pull the two rows out and put them at the bottom of the table.

Transuranium Elements Elements past uranium Elements past uranium Atomic numbers higher than 92 Atomic numbers higher than 92 Radioactive Radioactive Very short half lives Very short half lives Not found in nature Not found in nature Created in laboratories Created in laboratories

Radioactivity One element turning into another element One element turning into another element Half life = how fast the element changes Half life = how fast the element changes

Metalloids This line separates the metals from the nonmetals on the periodic table These are the metalloids B Si Ge As Sb Te Po

Semiconductors Metalloids Metalloids Only let electricity through in one direction Only let electricity through in one direction Used in modern electronics Used in modern electronics Cell phones Cell phones Video games Video games Computer chips Computer chips

Organic Compounds Historically believed to be created only by living organisms Historically believed to be created only by living organisms Contain carbon, hydrogen, oxygen, nitrogen and sulfur Contain carbon, hydrogen, oxygen, nitrogen and sulfur Chocolate

Nonmetallic Elements Insultators Insultators Brittle Brittle Dull Dull

Halogens Group 17 Group 17 F Cl Cl Br Br I “Salt forming” “Salt forming” Most reactive nonmetals Most reactive nonmetals

Reactivity of Halogens Combine with metals to form compounds called salts Combine with metals to form compounds called salts Sodium chloride Sodium chloride Magnesium iodide Magnesium iodide Fluorine is the most reactive element on Earth Fluorine is the most reactive element on Earth

Noble Gases Group 18 Group 18 He He Ne Ne Ar Ar Eight valence electrons, so they don’t react with anything Eight valence electrons, so they don’t react with anything Kr Kr Xe Xe Rn Rn