Basics Of ChemistryBasics Of Chemistry88thth Science 2012 Science 2012

Matter DefinedMatter Defined

►Matter – anything Matter – anything that has volume or that has volume or mass.mass.

► Everything you see Everything you see and don’t see.and don’t see.

DefinitionsDefinitions

► Element- pure Element- pure substance that substance that cannot be cannot be separated into separated into simpler substances simpler substances by physical or by physical or chemical means.chemical means. Represented by a Represented by a

symbol – Au stands symbol – Au stands for what?for what?

DefinitionsDefinitions

► Atom – Smallest Atom – Smallest particle into which particle into which an element can be an element can be divided and still be divided and still be the same the same substance, retaining substance, retaining its propertiesits properties

Evolution of the Atomic Evolution of the Atomic TheoryTheory

► Democritis – 440 BCDemocritis – 440 BC► Greek philosopher who said that if you cut a Greek philosopher who said that if you cut a

substance in half again and again and again substance in half again and again and again eventually you would have an eventually you would have an “uncuttable” “uncuttable” piecepiece

► said that all atoms made of a single material said that all atoms made of a single material formed into different shapes and formed into different shapes and they they join join togethertogether to make different materials to make different materials

► Greek word Greek word atomosatomos, which means , which means “indivisible”“indivisible”

John Dalton - 1803John Dalton - 1803

► Studied the Studied the atmosphere and other atmosphere and other gases and developed gases and developed atomic theory.atomic theory.

►Dalton demonstrated Dalton demonstrated that that elementselements combine in specific combine in specific proportionsproportions to make to make different substancesdifferent substances

John Dalton’s Atomic TheoryJohn Dalton’s Atomic Theory

► 1. All substances are 1. All substances are made of made of atomsatoms..

► 2. Atoms are small 2. Atoms are small particles that cannot particles that cannot be be created, divided, or created, divided, or destroyed.destroyed.

Dalton’s New System of Chemical Philosophy

Dalton’s Atomic Theory, Dalton’s Atomic Theory, continuedcontinued

► 3. Atoms of the 3. Atoms of the same elementsame element are are identical in size, mass and other identical in size, mass and other properties. properties.

► 4. Atoms of different elements 4. Atoms of different elements combine to make chemical combine to make chemical compounds.compounds.

► 5. In 5. In chemical reactions, atoms are , atoms are combined, separated, or rearranged.combined, separated, or rearranged.

J.J. Thomson - 1897J.J. Thomson - 1897

► discovered that discovered that there are there are small small particlesparticles inside the inside the atom, so atom, so the atom the atom can becan be divided divided into smaller partsinto smaller parts

JJ Thomson, continuedJJ Thomson, continued

► Experimented, using Experimented, using a cathode-ray tube a cathode-ray tube to discover to discover negative particlesnegative particles he called corpuscleshe called corpuscles

► these these negatively negatively charged particles charged particles found in found in all all atomsatoms are now are now calledcalled electronselectrons

Thomson’s ModelThomson’s Model

► Plum Pudding Plum Pudding modelmodel

►Described electrons Described electrons as scattered all as scattered all about the atomabout the atom

Ernest Rutherford - 1908Ernest Rutherford - 1908

Rutherford, continuedRutherford, continued

► Discovered a tiny, Discovered a tiny, extremely dense, extremely dense, positively charged positively charged region called a region called a nucleusnucleus

► Most of the Most of the atom’s atom’s massmass was in the was in the nucleus and nucleus and electrons traveled electrons traveled around the around the nucleusnucleus

Rutherford cont’dRutherford cont’d

► said the atom said the atom was mostly was mostly emptyempty space space

Niels Bohr – 1913Niels Bohr – 1913► said the said the electrons electrons

travel aroundtravel around the the nucleus in nucleus in definitedefinite pathspaths

Erwin Schrödinger and Erwin Schrödinger and Werner Heisenberg - 1926Werner Heisenberg - 1926

► Said Said electrons travel electrons travel in clouds, not in clouds, not definite pathsdefinite paths but but we still use the Bohr we still use the Bohr Model to represent Model to represent atoms.atoms.

The AtomThe Atom

Subatomic ParticlesSubatomic Particles

ProtonsDetermine the identity of the matter►positivelypositively charged particles charged particles►found in the found in the nucleusnucleus►Mass =1.67262158 × 10-27 kilograms

0.000000000000000000000000017 kg0.000000000000000000000000017 kg►Each proton is Each proton is 1 amu1 amu

AMU stands for Atomic Mass UnitAMU stands for Atomic Mass Unit

Subatomic ParticlesSubatomic Particles

NeutronsNeutrons are the glue that holds the protons together in the nucleus

►no chargeno charge►found in the found in the nucleusnucleus►mass is mass is 1 amu1 amu

Subatomic ParticlesSubatomic Particles

Electrons

Determine the reactivity►NegativelyNegatively charged charged►Found Found around the nucleusaround the nucleus within within electron cloudselectron clouds►MassMass is very small, is very small, almost zeroalmost zero

Atoms are NEUTRALAtoms are NEUTRAL

►Atoms are Atoms are neutralneutral because the because the number of number of protonsprotons equals equals the the number of number of electronselectrons..

How To Read a SquareHow To Read a Square

► 88

► OO► OxygenOxygen► 15.999415.9994

► Elements are Elements are identified by their identified by their atomic numberatomic number – – the number of the number of protons. Also protons. Also equals the number equals the number of electrons.of electrons.

► Chemical SymbolChemical Symbol► Element NameElement Name► Atomic MassAtomic Mass

PEN MethodPEN Method

► SLIDE, SLIDE, SLIDE, SLIDE, ROUND THE ROUND THE BOTTOM SUBTRACT BOTTOM SUBTRACT TOPTOP

► P = 8P = 8► E = 8E = 8►N = 8N = 8

► 88

► OO► OxygenOxygen► 15.999415.9994