Pudding and clouds

Atomic Models

Pudding and Clouds

Chem Catalyst:

• In the 5th century a Greek philosopher named Leucippus and his student, Democritus, said, “ All matter is made up of particles called atoms.”

• Do you think atoms are composed of smaller pieces?

• If there are smaller pieces of an atom , how would they differ from each other?

Connections to the past

On the cards used in “Create a Table”:

• What do you think the size of the circle represents?

• What do you think the pegs or sticks represent?

Atoms

–Atoms are extremely small particles, which cannot be seen with the eye or regular school microscopes

–An atom is the smallest amount of a element that can exist and still have the properties of that element

–All matter is made up of atoms.

Charge

• Fundamental property of atom and their parts

• Related to the forces pushing or pulling the atom pieces

• A piece can have positive, negative or neutral charge

For most of time

• People were talking about atoms without having ever actually seen any picture of one.

• They came up with visual and descriptive representations of concept of an atom, called a model or theory

Atomic model

Atomic model or theory represent the best explanation for the design and workings of an atom by a specific person or group, based on the scientific evidence available

As new evidence is gathered, models are refined and changed.

Theories and models are not casual ideas

• Not proposed without testing, and research • Then it is tested repeatedly by the scientific

community• It is valid until contrary evidence is found,

then modified or discarded.

Unit 1 • Investigation III

The Big Question

–How have chemists thought about the atom through history?

Goal of the section

• By the completion of the section you should be able to:– Identify the major components of any atom– Use the concepts of the latest theory on atomic

structure to explain how a atom is set up and operates

– Understand the 5 major versions of atomic theory and be able to compare and contrast them

Unit 1 • Investigation III

Activity

• Purpose: This lesson will introduce you to various models for the atom that have appeared over the past two hundred years. The descriptions of five models of the atom are on a separate handout.

(cont.)

Part 1Organize the models in

chronological order• Based on information listed on the cards,

organize the models in chronological order.

• In comp book List models A thru E from earliest model to current model. Explain what evidence you used to arrange models

Part 2: Organizing Models and evidence by

Year and Name

• A 2nd set of handouts will be given to students.• Use 2nd handout set to determine if your original

chronological order of models was correct.

• In Comp book, create and complete a chart with the following information

Does Model Indicate Existence of:

Model Name

People behind model concept

Electron Proton Neutrons Nucleus Electrons moving in paths or orbits

Electrons moving randomly

BilliardBall

Plum Pudding

Nuclear

Solar System

Current

Part 3: Matching evidence with Models

• Each pair of students will then be given 6 pieces of evidence about atoms.

• For each piece of evidence, compare the information of 2 models to determine which model supports or agrees with the piece of evidence the best. Explain your answer in your composition book

Unit 1 • Investigation III

• Five Models of the Atom

(cont.)

Five authors and their big ideas

• John Dalton Atom as a solid sphere, Different atom for each element

• JJ Thompson Electrons• Ernest Rutherford Nucleus• Niels Bohr Electron Orbitals/Shells

Protons• Heisenberg,Chadwick Electron Cloud / Neutron

Acting out the models

Alpha particles

• Helium nucleus stripped of its electrons

Current Model1. Every atom is composed of a tiny, dense, positively charged nucleus located at

center of atom. Nucleus is composed of positively charges protons and neutrally charged neutrons

2. Mass of a proton and neutron are the same

3. Electron Cloud: region of atom around the nucleus occupied by fast moving, almost mass-less, negatively charged electrons.

4. An atom (and electron cloud) is made up mostly of space, almost all mass of atom is located in the nucleus

5. Electrons do not all move at the same distance from the nucleus. Some are closer or farther away ,depending on amount of KE they possess

6. Paths of electrons are not orbits like planets, but more randomized. It is impossible to predict the exact location of an electron at a point of time.

Electron Proton Neutron Nucleus

Charge

Mass

Location

Part 4

• In comp book, write Definitions for:

• Proton• Neutron• Electron• Nucleus• Electron Cloud, orbit, shell• Void

Difference between clouds, orbits and shells

• Electron cloud: Includes all space in an atom outside of a nucleus where an electron may be found, mostly void

• Electron Orbit: 2 Dimension representation of an electron’s position based on the amount of KE energy it possesses

• Electron Shell: 3 dimensional representation of a electron orbit

Unit 1 • Investigation III

Notes (cont.)

Unit 1 • Investigation III

Wrap-Up

–All matter is made up of extremely small particles called atoms. These particles are too small to be seen even with a regular microscope.– Science is theoretical and dynamic. Models

and theories are continually being revised, refined, or replaced with new models and theories.

Check in

1) Does a nucleus have a positive, negative or neutral charge

2) Which has more mass?a) A proton from a Helium atomb) An electron from a Helium atomc) A neutron from a Helium atomd) A nucleus from a helium atome) An alpha particle

Check in#3 Match the Scientist’s name to the Model Name

below to which he is associated. Organize from oldest (1) to most recent (5)

Chadwick Plum PuddingBohr Solar SystemDalton Current ModelThomson Billiard BallHeisenberg NucleusRutherford