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How substances are named:
Depends on what they are composed of Elements have only one name which is based on their identity (names on the periodic table) and is represented by a unique symbol Some Element names are attached to another word that further describes them: Ex. Hydrogen gas, liquid Bromine, molecular Nitrogen, atomic Oxygen MEMORIZE: Diatomic elements
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Tro: Chemistry: A Molecular Approach, 2/e
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About ¾ of the elements are classified as metals
About ¾ of the elements are classified as metals. They have a reflective surface, conduct heat and electricity better than other elements, and are malleable and ductile. Metals generally tend to form (+) positive ions when charged. Most of the remaining elements are classified as nonmetals. Their solids have a non-reflective surface, do not conduct heat and electricity well, and are brittle. Nonmetals generally tend to form (-) negative ions when charged. A few elements are classified as metalloids. Their solids have some characteristics of metals and some of nonmetals.
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How ions form: Cations (+) positive ions have more protons than electrons. How? They have lost 1 or more electrons Anions (-) negative ions have more electrons than protons. How? They have picked up 1 or more electrons
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Ion Charge and the Periodic Table
The charge on an ion can often be determined from an element’s position on the Periodic Table Metals always form positively charged cations For many main group metals, the charge = the group number Nonmetals form negatively charged anions For nonmetals, the charge = the group number − 8 Tro: Chemistry: A Molecular Approach, 2/e
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Tro: Chemistry: A Molecular Approach, 2/e
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Practice – What is the charge on each of the following ions?
potassium cation sulfide anion calcium cation bromide anion aluminum cation K+ S2− Ca2+ Br− Al3+ Tro: Chemistry: A Molecular Approach, 2/e
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Metals can be shaped Solids at room temperature, except Hg
Reflective surface shiny Conduct heat Conduct electricity Malleable can be shaped Ductile can be drawn or pulled into wires Lose electrons and form cations in reactions About 75% of the elements are metals Lower left on the table Tro: Chemistry: A Molecular Approach, 2/e
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Nonmetals Found in all three states Poor conductors of heat
Sulfur, S(s) Nonmetals Found in all three states Poor conductors of heat Poor conductors of electricity Solids are brittle Gain electrons in reactions to become anions Upper right on the table except H Bromine, Br2(l) Chlorine, Cl2(g) Tro: Chemistry: A Molecular Approach, 2/e
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does not conduct heat well
Metalloids Show some properties of metals and some of nonmetals Also known as semiconductors Properties of Silicon shiny conducts electricity does not conduct heat well brittle Tro: Chemistry: A Molecular Approach, 2/e
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The Modern Periodic Table
Elements with similar chemical and physical properties are in the same column Columns are called Groups or Families designated by a number and letter at top Rows are called Periods Each period shows the pattern of properties repeated in the next period Tro: Chemistry: A Molecular Approach, 2/e
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The Modern Periodic Table
Main group = representative elements = “A” groups Transition elements = “B” groups all metals Bottom rows = inner transition elements = rare earth elements metals really belong in Period 6 & 7 Tro: Chemistry: A Molecular Approach, 2/e
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Tro: Chemistry: A Molecular Approach, 2/e
find table that includes rare earth elements Tro: Chemistry: A Molecular Approach, 2/e
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= Alkali metals = Alkali earth metals = Noble gases = Halogens
= Lanthanides = Actinides = Transition metals add pictures of elements from text Tro: Chemistry: A Molecular Approach, 2/e
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Important Groups - Hydrogen
Nonmetal Colorless, diatomic gas very low melting point and density Reacts with nonmetals to form molecular compounds HCl is acidic gas H2O is a liquid Reacts with metals to form hydrides metal hydrides react with water to form H2 HX dissolves in water to form acids Tro: Chemistry: A Molecular Approach, 2/e
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Important Groups – Alkali Metals
Group IA = Alkali Metals Hydrogen usually placed here, though it doesn’t really belong Soft, low melting points, low density Flame tests ® Li = red, Na = yellow, K = violet Very reactive, never find uncombined in nature Tend to form water-soluble compounds, therefore salt is crystallized from seawater then molten salt is electrolyzed colorless solutions React with water to form basic (alkaline) solutions and H2 2 Na + 2 H2O ® 2 NaOH + H2 releases a lot of heat lithium sodium potassium rubidium cesium Tro: Chemistry: A Molecular Approach, 2/e
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Important Groups – Alkali Earth Metals
Group IIA = Alkali earth metals Harder, higher melting, and denser than alkali metals Mg alloys used as structural materials Flame tests ® Ca = red, Sr = red, Ba = green Reactive, but less than corresponding alkali metal Form stable, insoluble oxides from which they are normally extracted Oxides are basic = alkaline earth Reactivity with water to form H2 Be = none; Mg = steam; Ca, Sr, Ba = cold water Tro: Chemistry: A Molecular Approach, 2/e
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Important Groups – Halogens
Group VIIA = halogens Nonmetals F2 and Cl2 gases; Br2 liquid; I2 solid All diatomic Very reactive Cl2, Br2 react slowly with water Br2 + H2O ® HBr + HOBr React with metals to form ionic compounds HX all acids HF weak < HCl < HBr < HI fluorine chlorine bromine iodine astatine Tro: Chemistry: A Molecular Approach, 2/e
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Important Groups – Noble Gases
Group VIIIA = Noble Gases All gases at room temperature very low melting and boiling points Very unreactive, practically inert Very hard to remove electron from or give electron to Tro: Chemistry: A Molecular Approach, 2/e
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