Structure of Structure of MatterMatter

Structure of Structure of MatterMatter

History of the Atom

History of the Atom

The Greek ModelThe Greek ModelThe Greek ModelThe Greek Model

Greek scholar: Democritus

developed the idea that matter is made of particles that are indivisible (atomos).

Greek scholar: Democritus

developed the idea that matter is made of particles that are indivisible (atomos).

The Dalton ModelThe Dalton ModelJohn Dalton- English chemist who proposed the first atomic theory.

John Dalton- English chemist who proposed the first atomic theory.

Dalton’s Atomic TheoryDalton’s Atomic Theory All elements are composed of indivisible particles called atoms. All atoms of the same element are identical. Atoms of different elements are different. When a chemical reaction occurs, the atoms are simply rearranged in a fixed whole-number ratio.

All elements are composed of indivisible particles called atoms. All atoms of the same element are identical. Atoms of different elements are different. When a chemical reaction occurs, the atoms are simply rearranged in a fixed whole-number ratio.

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Vacuum tube

Metal Disks

Thomson discovered the first component part of the atom: the electron, a particle with a _____ electric charge.

Thomson discovered the first component part of the atom: the electron, a particle with a _____ electric charge.

DISCOVERY OF THE ELECTRON  

 

DISCOVERY OF THE ELECTRON  

 

J.J. Thomson’s Model or the “plum pudding” Model

J.J. Thomson’s Model or the “plum pudding” Model

He proposed that an atom was made of ________ portion(pudding).

Spread throughout these positive charges were the negative charges called ________ (plums).

He proposed that an atom was made of ________ portion(pudding).

Spread throughout these positive charges were the negative charges called ________ (plums).

The Rutherford Gold Foil Experiment

The Rutherford Gold Foil Experiment

   

1. 1. The atom contains The atom contains a tiny BUT dense center a tiny BUT dense center called the called the nucleus.nucleus.

2. 2. The nucleus isThe nucleus is positivelypositively charged. charged.

3. 3. The The electronselectrons move move around in the around in the empty empty spacespace of the atom of the atom surrounding the nucleus.surrounding the nucleus.

1. 1. The atom contains The atom contains a tiny BUT dense center a tiny BUT dense center called the called the nucleus.nucleus.

2. 2. The nucleus isThe nucleus is positivelypositively charged. charged.

3. 3. The The electronselectrons move move around in the around in the empty empty spacespace of the atom of the atom surrounding the nucleus.surrounding the nucleus.

Rutherford's Nuclear ModelRutherford's Nuclear ModelRutherford's Nuclear ModelRutherford's Nuclear Model

These concepts appear in the These concepts appear in the finals always – so they are very, finals always – so they are very,

very, very IMPORTANT!!! very, very IMPORTANT!!!

The atom is made The atom is made mostly of mostly of emptyempty space with a dense and space with a dense and

positively-charged nucleus called positively-charged nucleus called the nucleus !!!the nucleus !!!

Hypothesis Hypothesis : : Rutherford expected the a-Rutherford expected the a-particles to pass undeflected through the particles to pass undeflected through the atoms. atoms. ResultsResults: : Rutherford observed that a small Rutherford observed that a small fraction of the a-particles were ______; to fraction of the a-particles were ______; to explain the observation, he proposed the explain the observation, he proposed the ________ model of the atom. ________ model of the atom.

ExplanationExplanation: : To deflect the energetic a-To deflect the energetic a-particles, the particles, the ________________ must be must be densedense, with , with ________________ charge. charge. For the fraction deflected to be small, the For the fraction deflected to be small, the nucleus must be (small,big) , the atom must nucleus must be (small,big) , the atom must be be mostly empty space.mostly empty space.

James Chadwick – discovered James Chadwick – discovered the the neutrons neutrons

Neutrons are neutral particlesNeutrons are neutral particles

James Chadwick – discovered James Chadwick – discovered the the neutrons neutrons

Neutrons are neutral particlesNeutrons are neutral particles

Bohr’s ModelBohr’s ModelElectrons in atoms could Electrons in atoms could

exist only at certain exist only at certain energy levelsenergy levels around the around the nucleus in regions of nucleus in regions of space shaped like the space shaped like the surface of a ball.surface of a ball.

Electrons can jump from Electrons can jump from the lowest energy level the lowest energy level (ground state) to a (ground state) to a higher energy level higher energy level (excited state).(excited state).

As electrons return to As electrons return to the lowest energy level the lowest energy level again, the same amount again, the same amount of energy the atom of energy the atom absorbed will be absorbed will be releasedreleased in the form of in the form of light.light.

Electrons in atoms could Electrons in atoms could exist only at certain exist only at certain energy levelsenergy levels around the around the nucleus in regions of nucleus in regions of space shaped like the space shaped like the surface of a ball.surface of a ball.

Electrons can jump from Electrons can jump from the lowest energy level the lowest energy level (ground state) to a (ground state) to a higher energy level higher energy level (excited state).(excited state).

As electrons return to As electrons return to the lowest energy level the lowest energy level again, the same amount again, the same amount of energy the atom of energy the atom absorbed will be absorbed will be releasedreleased in the form of in the form of light.light.

Absorb energy

Energy released

Spectrum of hydrogen

Spectrum of neon

Planetary Model Planetary Model

3-D orbits

The Charge-Cloud ModelThe Charge-Cloud Model

                   Scientists now Scientists now describe the describe the possible positions of possible positions of electrons in terms of electrons in terms of __________ __________   

Wave-Mechanical (charge-cloud) Wave-Mechanical (charge-cloud) ModelModelWave-Mechanical (charge-cloud) Wave-Mechanical (charge-cloud) ModelModel

An__________ is the distribution of An__________ is the distribution of probabilitiesprobabilities: it is : it is thickest in the thickest in the regions where we are most likely regions where we are most likely to find the electronto find the electron (orbital)(orbital) at at any given moment.any given moment.

OrbitalOrbital – 3-dimensional, cloudlike – 3-dimensional, cloudlike spacespace Electrons have dual Electrons have dual characteristics:characteristics: wavewave and and particleparticle

Atomic Atomic StructureStructureAtomic Atomic

StructureStructure

Periodic Table of Periodic Table of ElementsElements

Periodic Table of Periodic Table of ElementsElements

Symbol / Representation:Symbol / Representation: Symbol / Representation:Symbol / Representation:

AA – the mass no.– the mass no.

ZZ – the atomic no. – the atomic no.

XX – the symbol of – the symbol of the atomthe atom

Mass No.

Atomic No.

Subtract !!!

Neutrons

Atomic Atomic RepresentationRepresentation

Atomic Atomic RepresentationRepresentation

Outside the nucleus: Outside the nucleus: Outside the nucleus: Outside the nucleus:

Shell or energy levelShell or energy level – – main area main area where the electrons are foundwhere the electrons are found

Sublevel or SubshellSublevel or Subshell – – subdivision of subdivision of the main shellthe main shell

OrbitalOrbital – – a a three-dimensional spacethree-dimensional space where the electron is found with where the electron is found with greatest greatest probability probability oror

chance .chance .

Shell or energy levelShell or energy level – – main area main area where the electrons are foundwhere the electrons are found

Sublevel or SubshellSublevel or Subshell – – subdivision of subdivision of the main shellthe main shell

OrbitalOrbital – – a a three-dimensional spacethree-dimensional space where the electron is found with where the electron is found with greatest greatest probability probability oror

chance .chance .