Chapter 4.1Chapter 4.1An Atomic Model of An Atomic Model of

MatterMatter•The Greek ModelThe Greek Model• Dalton’s modelDalton’s model• Thompson’s modelThompson’s model•Rutherford’s modelRutherford’s model•Bohr’s modelBohr’s model• Modern modelModern modelHow Elements Are Formed Clip

http://www.youtube.com/watch?v=uKqvjEE0wFg

The Greek The Greek modelmodel

Democritus said that Democritus said that matter could not be matter could not be divided into smaller divided into smaller and smaller pieces and smaller pieces forever. He proposed forever. He proposed the atom or Atomos the atom or Atomos meaning –not divisiblemeaning –not divisible

These philosophers These philosophers were called Atomistwere called Atomist

Indirect EvidenceIndirect EvidenceThe atomist only had The atomist only had indirect evidence they did indirect evidence they did not have microscopes…not have microscopes…

This is evidence that you This is evidence that you get without seeing or get without seeing or touching ittouching it

Dalton’s ModelDalton’s ModelDaltons proposed a 4 part theory Daltons proposed a 4 part theory

about atomsabout atoms1. All elements are Composed of 1. All elements are Composed of

atomsatoms2. Atoms of the same element are 2. Atoms of the same element are

alikealike3.Atoms of different elements 3.Atoms of different elements

are differentare different4. Compounds are formed by 4. Compounds are formed by

the joining of 2 or more elementsthe joining of 2 or more elements

Thomson’s ModelThomson’s ModelAccording to Thomson the According to Thomson the atom was made of a pudding atom was made of a pudding like positively charged like positively charged material throughout which material throughout which negativelynegatively charged electrons charged electrons

were scattered like were scattered like plums in pudding. plums in pudding.

Rutherford’s Rutherford’s ModelModelRutherford said that Rutherford said that

the positive the positive particles were particles were contained in the contained in the nucleus and the nucleus and the negative charged negative charged particles were particles were scattered outside scattered outside

The Gold Foil Experiment Cliphttp://www.dnatube.com/video/2811/Nucleus-of-an-atom

Bohr’s ModelBohr’s ModelBohr stated that Bohr stated that electrons orbited electrons orbited around the around the nucleus like nucleus like planets around the planets around the sun and each orbit sun and each orbit was a different was a different energy level.energy level.

The Modern The Modern ModelModel

Electrons are behaving Electrons are behaving more like waves than more like waves than planets and they vibrate planets and they vibrate back and forth.back and forth.

They are like bees around a They are like bees around a hive.hive.

History Timeline of the Atom

Building blocks of Building blocks of moleculesmolecules

Atoms are the smallest Atoms are the smallest part of an element that part of an element that acts like that elementacts like that element

Atoms are composed of 3 Atoms are composed of 3 smaller particles: Protons, smaller particles: Protons, electrons and neutrons.electrons and neutrons.

Modern

Modern Model of AtomModern Model of Atom