Post on 12-Jan-2016
Chapter 3 – Classification of Matter
Elements – Distribution, Names, SymbolsElements - Metals, Nonmetals, MetalloidsDiatomic MoleculesChemical FormulasMixtures
Element:Element: A substance that cannot be A substance that cannot be decomposed into simpler substances by decomposed into simpler substances by chemical means.chemical means.
ElementsElements
Make up our Make up our chemical chemical alphabet.alphabet.
Over 100 Over 100 known known elementselements
Element:Element: Our building block of all substances. Our building block of all substances. Numbered in order of increasing complexityNumbered in order of increasing complexity
ElementsElements
•Elements through 92 are known to occur in nature. [with 4 exception Technetium (43), Promethium (61), Astatine (85), Francium (87)]•Above 92 only Plutonium (94) occur in nature.•Above 92 all elements must be synthesized in the laboratories in small quantities
Elements
Most substances can be decomposed into two or more simpler substance.
Water = Hydrogen and OxygenSugar = Carbon, Hydrogen, and
OxygenSalt = Sodium and Chloride
Elements
The smallest particle of an element that can exist is an atom, which is also the smallest unit of an
element that can enter into a chemical reaction.
Atoms are made up of subatomic particles that will be discussed later in the semester.
Distribution of ElementsElements are distributed unequally in nature
Ten elements make up 99% of the mass of the Earths Crust, seawater, and atmosphere
Oxygen is about 50% of this massTwo elements are liquids at room
temperature Bromine and Mercury
Eleven elements are gases Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine,
Helium, Neon, Argon, Krypton, Xenon, and Radon
All other elements are solids
Distribution of Elements
Elements are distributed unequally in nature Figure a, shows
the distribution in the glalaxies
Figure b, shows the distribution in Earths crust
Figure c, shows the distribution in Humans
Famous-Scientists
• Einsteinium: named for Albert Einstein.
Location • Germanium: discovered in 1866 by a German chemist.
German-Color
• Bismuth: from the German weisse mass which means white mass.
Greek-Color
• Iodine: from the Greek iodes meaning violet.
Latin-Property
• Fluorine: from the Latin fluere meaning to flow. The fluorine containing ore fluorospar is low melting.
Sources of Element Names
Symbols of the Elements
Each element has an abbreviation. Iodine is taken from Greek work iodes, meaning violet. Bismuth is from German, weisse masse, white mass. Germanium is due to it’s discovery by a German Others are named in commemoration of famous
scientist
Symbols of the ElementsEach element has an abbreviation –
Symbols Some (14) have single letterThe rest have 2 letters
The symbol stands for the element itself For one atom of the element For a particular quantity of the element
Rules. Symbols have either one or two letters If one letter – Capitalized If two letters – First letter capitalized – second
letter lower case
Ne neon
Rules governing symbols of the elements are:
1. Symbols have either one or two letters.
2. If one letter is used it is capitalized.
3. If two letters are used, only the first is capitalized.
H hydrogenC carbon
Ba barium
Symbols of the ElementsSymbols and names are on the inside cover.Possibly make flash cards to learn these symbols.
Metal, Nonmetals, and Metalloids
Metal, Nonmetals, and MetalloidsMetals
Most of the elements are metalsSolids at RT (except mercury)Malleable – Can be hammered or rolled into sheets.Ductile – Can be Drawn into wiresHigh Melting pointHigh densityCombine with non-metals to form ionic compoundsOften found as alloys – Homogenous mixtures
Metal, Nonmetals, and Metalloids
A few of the less reactive metals such as copper, silver and gold are found in the free state.
Metals can mix with each other to form alloys.
Brass is a mixture of copper and zinc. Bronze is a mixture of copper and tin. Steel is a mixture of carbon and iron.
Metal, Nonmetals, and Metalloids
NonmetalsLow melting points and densityGenerally poor conductors of heat and conductivityCombine with one another to form molecular compounds
MetalloidsProperties are intermediate between metals and nonmetals Some are raw material for semiconductor
boron silicon germanium arsenic antimony tellurium polonium
Metalloids
CompoundsCompounds
Compound:Compound: A substance with a A substance with a constant composition that can be constant composition that can be broken down into elements by broken down into elements by chemical processes.chemical processes. Atoms in a compound are always Atoms in a compound are always whole number ratioswhole number ratios Two types - molecular and ionicTwo types - molecular and ionic
Compounds
Molecule – The smallest uncharged individual unit of a compound formed from 2 or more atoms
Ion – Positively or negatively charged atom or group of atoms.Held together by attractive forces from
positively and negatively charged ions Cation – Positively charged Anion – Negatively charged
Compounds can be classified as molecular or ionic. Ionic compounds are held together by attractive forces between their positive and negative charges. Molecular compounds are held together by covalent bonds.
Diatomic Molecules Special type of molecule Contain 2 atoms – alike or different Seven elements are diatomic molecules
Hydrogen - H2 Oxygen - O2
Nitrogen - N2 Fluorine - F2 Chlorine - Cl2 Bromine - Br2 Iodine - I2
Need to know these!!!!
Hydrogen HNot found in nature.
Hydrogen H2
Found in nature.
Nitrogen NNot found in nature.
Nitrogen N2
Found in nature.
Occurrence of Diatomic Molecules
Chemical Formulas
Used as abbreviations for compounds Shows the symbols and the ratio of the elements
in a compound
H2O Indicates 2 Hydrogens and one Oxygen
H2SO4 Indicates 2 Hydrogens, 1 Sulfur, and 4 Oxygen
Water has the formula H2O.
H2 O2 H2O
• It does not contain free hydrogen, H2 or free oxygen, O2.
• The H2 part of H2O means that 2 atoms of hydrogen are combined with one atom of oxygen in the water molecule.
Serve as abbreviations of the names of compounds.
CaCl2calciumchloride
chemicalformulas
chemicalformulas
Tell which elements the compound is composed of and how many atoms of each element are present in a formula unit.
CaCl2calciumchlorine
chemicalformulas
Show the symbols of the atoms of the elements present in a compound.
CaCl2Ca calciumCl chlorine
chemicalformulas
Show the ratio of the atoms of the elements present in a compound.
2 Cl1 Ca
CaCl2
Chemical Formulas Formula of a compound contains the symbols of
all the elements Formula contains one atom of an element the
number 1 subscript is left out Formula contains more than one atom of the
same element – the number is indicated as a subscript written to the right of the symbol of that atom
When a formula contains more than one group of atoms occur as a unit – a parentheses is place around the group with the number subscripted Ca(NO3)2
indicates 3 H atoms
indicatesthe element phosphorous (P)
indicatesthe element hydrogen (H)
indicatesthe element oxygen (O)H3PO4
indicates 4 O atoms
Chemical Formulas
Ba3(PO4)2
indicates three Ba atoms
3-4phosphate (PO )
indicates two
groups
indicatesthe element barium
indicates the phosphate group composed of one phosphorous atom and four oxygen atoms
Chemical Formulas
Formulas written as H2O, H2SO4, Ca(NO3)2 and C12H22O11
show only the number and kind of each atom contained in the compound; they do not show the arrangements of the atoms in the compound or how they are chemically bonded to each other.
Chemical Formulas
Concepts - Chapter 3
Classify – elements, compounds, mixtures Write symbols or name for common elements Understand chemical formulas Differentiate between atoms, molecules, ions Know some characteristics of metals,
nonmetals and metalloids Recognize elements that occur as diatomic
molecules