1 chapter 11 the chemical elements dr. babar ali

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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