1 chapter 11 the chemical elements dr. babar ali
TRANSCRIPT
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Chapter 11
THE CHEMICAL
ELEMENTS
Dr. Babar Ali
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CHAPTER OUTLINE
Chemistry & Matter Classification of
Matter Mixtures Pure substances Periodic Table
Metals & Non-metals Metalloids Periods & Groups Solutions Chemical Formulas Naming Compounds
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CHEMISTRY& MATTER
Chemistry is the science that deals with the composition and structure of matter, and its changes
Matter is anything that has mass, and occupies space
Matter can be classified by its physical state as gas, liquid or solid
Matter can also be classified by its composition as pure substance or mixture
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CLASSIFICATIONOF MATTER
MATTER
Anything that has mass
PURE SUBSTANCE
Fixed composition & properties
MIXTURE
Variable composition & properties
Mixtures can be converted into pure substances by simple physical processes (e.g. filtration, evaporation)
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MIXTURES
HOMOGENEOUS
Uniform composition & properties
MIXTURE
Variable composition & properties
HETEROGENEOUS
Non-uniform composition & properties
Tea, Coke Ink
Salad dressing Cement
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PURE SUBSTANCES
PURE SUBSTANCE
Fixed composition & properties
COMPOUNDS
2 or more elements chemically combined
ELEMENTS
Composed of one type of atom
Compounds can be converted into elements by chemical processes or reactions (e.g. electrolysis)
hydrogen, copper, iron
water, sugar salt
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PERIODIC TABLE
Arrangement of elements based on their atomic masses (A) was first proposed by the Russian chemist, Dmitri Mendeleev in 1869
In the modern periodic table the elements are arranged according to their atomic # (Z)
The elements are generally classified as
metals, nonmetals and metalloids
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PERIODIC TABLE
Metals Non-metals
Metalloids
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PERIODIC TABLE
Metallic character increases going down a groupMetallic character decreases going across a period
Most metallic elements
Least metallic element
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PERIODIC TABLE
Metals
Non-metalsMetalloids
7 elements exist as diatomic molecules
others exist as monatomic (one atom)
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PROPERTIES OF METALS & NON-METALS
Metals Non-metals
Mostly solid Can be solid, liquid or gas
Have shiny appearance Have dull appearance
Good conductors of heat & electricity
Poor conductors of heat & electricity
Malleable & ductile Brittle (if solid)
Lose electrons Gain or share electrons
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METALLOIDS
Metalloids are elements that possess some properties of metals and some of non-metals
The most important metalloids are silicon (Si) and germanium (Ge) which are used extensively in computer chips
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PERIODS & GROUPS
The periodic table is composed of periods (rows) and groups or families (columns)
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PERIODS & GROUPS
Elements in the same group or family have similar properties, and are commonly referred to by their traditional names
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More on GROUPS
Elements in groups 1-2 and 13-18 are referred to as main-group or representative groups
Alkali metals are soft metals that are very reactive. They often react explosively with other elements
Noble gases are unreactive gases that are commonly used in light bulbs
Halogens are the most reactive nonmetals, and occur in nature only as compounds
Group 2 elements are called alkaline-earth metals. These metals are less reactive than alkali metals
The group of metals in between the main group elements are called transition metals
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SOLUTIONS
Solutions are homogeneous mixtures made from two substances
SolutionsSolute Solvent
Substance being
dissolved
Substance dissolving
solute
Solutes and solvents can be any of the 3 phases of matter: solids, liquid or gas
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SOME COMMONSOLUTIONS
Solution Solute Solvent
air oxygen nitrogen
soda water carbon dioxide water
antifreeze ethylene glycol water
wine ethyl alcohol water
saltwater salt water
brass copper zinc
steel carbon iron
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SOLUTIONS
Most common solutions have water as solvent and are called aqueous
Solutions that do not contain the maximum amount of solute dissolved in them are called unsaturated
Solutions that contain the maximum amount of solute dissolved in them and cannot dissolved anymore solute are called saturated
Solutions that contain more than the maximum amount of solute dissolved in them are called supersaturated
Supersaturated solutions are unstable and can be made to form crystals with the slightest disturbance
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Rules aboutCHEMICAL FORMULAS
Elements combine chemically to form compounds Each represented by a chemical formula
The more metallic element is written first followed by the less metallic element
Subscripts are used to indicate the # of atoms of each element in the compound
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CHEMICALFORMULAS
NaCl
Indicates 1 atom of sodium
Indicates 1 atom of chlorine
More metallic
Less metallic
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CHEMICALFORMULAS
CO2
Indicates 1 atom of carbon
Indicates 2 atoms of oxygen
More metallic
Less metallic
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CHEMICALFORMULAS
H2SO4
Indicates 2 atoms of hydrogen Indicates 4 atoms
of oxygenIndicates 1 atom
of sulfur
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CHEMICALFORMULAS
Ca(NO3)2Indicates 1 atom
of calcium
Indicates a nitrate groupComposed of 1
nitrogen and 3 oxygens
Indicates 2 nitrate groups
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NAMING BinaryCOMPOUNDS
To name a binary (2-element) compound of a metal and non-metal, 1st name the metal followed by the non-metal with ending changed to –ide.
Binary compounds of a Metal & a Non-metal
NaCl sodium chloride
Al2O3 aluminum oxide
Ca3N2 calcium nitride
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NAMINGCOMPOUNDS
To name a binary compound of 2 non-metals, the more metallic element is written 1st, followed by the 2nd element with the –ide ending
Binary compounds of a 2 Non-metals
HCl hydrogen chloride
CS2 carbon disulfide
PBr3 phosphorous tribromide
The number of atoms for each element is indicated by Greek prefixes: mono-(1); di-(2); tri-(3);tetra-(4); penta-(5); hexa-(6); hepta-(7)
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THE END