Models of the Atom: A Historical perspective

Models of the Atom: A Historical perspective

Democritus Democritus He asked: Could matter be divided into smaller and smaller pieces forever, or was there a limit to the number of times a piece of matter could be divided? 400 B.C. His theory: thought matter could not be divided indefinitely There was a limit to how far you could divide matter. You would eventually end up with a piece of matter that could not be cut

He named the smallest piece of matter atomos, meaning not to be cut Aristotle Very famous Greek philosopher Believed matter could be divided smaller and smaller pieces forever

Believed that matter was made of a combination of four elements: earth, fire, water, air Aristotle was wrong. However, his theory persisted for 2000 years. PIECES OF CARBON An atom is the smallest particle that an element

can be divided and still be that element. For example the smallest particle of carbon is a single atom of carbon. If you divide it is no longer carbon anymore. CARBON ATOM 1800 -Dalton proposed a modern atomic model based on experimentation not on pure reason

All matter is made of atoms Atoms of the same element are identical Each element has different atoms Atoms of different elements combine in constant ratios to form compounds. Atoms are rearranged in reactions. His ideas account for the law of conservation of mass (atoms are neither

created nor destroyed) and the law of constant composition (elements combine in fixed ratios). Accidental discovery of the cathode ray Discovery led to the development of the television Joseph John Thompson

What particle did Thompson discover? found that atoms could sometimes eject a far smaller negative particle which he called an ELECTRON Thompson develops the idea that an atom was made up of electrons scattered unevenly within an elastic sphere This sphere contained a soup of positive charge to balance the electron's charge electrons similar to plums in a pudding or

chocolate chips in ice cream. PLUM PUDDING MODEL Negative electron Positive charge spread over sphere Developed the charge of an atom e- Rutherford shot alpha () particles at gold foil Zinc sulfide screen

Thin gold foil Lead block Radioactive substance path of invisible particles Most particles passed through So, atoms are mostly empty space Some positive -particles deflected or bounced back! Thus, a nucleus is positive & holds most of an atoms mass

Electrons orbit the nucleus in shells Electrons can be bumped up to a higher shell if hit by an electron or a photon of light There are 3 types of subatomic particles. electrons (e) protons (p+) neutrons (n0) They have: no charge Elements are often symbolized with their mass number and atomic number

The periodic table give you all this information For now, round the mass # to a whole number # of protons = # of electrons = atomic number Mass number atomic number = # of protons E.g. Oxygen:

16 8O Nuclear Symbol Particle Charge Mass Proton + charge 1

Neutron No charge 1 Electron - Charge nil ATOMIC STRUCTURE EXAMPLE Atomic mass

the number of protons and neutrons in an atom 4 Atomic number the number of protons in an atom 2 He All of these pieces of information (numbers) are obtained from your

periodic table Atomic number = number of electrons = number of protons Practice Atomic Ca Ar Br Mass p+ n0 e

Copy the table right below your notes and fill in the information that is required of you. Use the periodic table to fill in this information. Symbol Calcium Neon Magnesi um Sodium Lithium Oxygen Carbon Potassiu m Silicon Chlorine

Atomic number Mass p+ n0 e-

Recently Viewed Presentations

  • Sociology The Basics

    Sociology The Basics

    If culture is where we choose to live, society is the world we can't avoid. Two or more people with something, anything in common. What is Sociology?!?! Sociological perspective- The sociological perspective is a perspective on human behavior and its...
  • Title Of Presentation

    Title Of Presentation

    Template: Mary Feil-Jacobs (maryjf), Heather Tall, Slidework LLC, Claire Hoover, Silverfox Productions Formatting: Event Date: June 2-6, 2008 Event Location: Orlando ...
  • MIS 648 Presentation Notes: Section X

    MIS 648 Presentation Notes: Section X

    Methodology Secondary data sources (World Bank plus others) for 1995 and 2001 Electrification Level = TV sets per 1000 ELF index quantifies ethnolinguistic fractionalization Correlational studies with regression analysis.


    Adapt number of items, delete essay questions. Difficulty. Focus on key concepts. Alternate Goals. Adapt . outcome expectations while using same . materials. Substitute/Parallel Curriculum. Student works on computer skills or functional activity related . to what is being done...
  • Basic Continuous Improvement 8 S I M P

    Basic Continuous Improvement 8 S I M P

    This training is the basis for the LEAN operator training and we expect that you actively participate to implement it . A point is to develop your ability to live this process as a model/example. This is just as important...
  • Slope Stability - Binus University

    Slope Stability - Binus University

    course : s0705 - soil mechanic year : 2008 topic 7 slope stability content slope failure and slope stability (session 25-26 : f2f) bishop method (session 25-26 : f2f) slope failure causal factor of failure the slope is too steep...
  • Silicon Controls The Road to 65% Average Fill

    Silicon Controls The Road to 65% Average Fill

    card is certified as part of the product, show that the battery is an integral part of the product, highlight the detail in engineering - a "post" to store battery nuts etc. Ease of Deployment. Quick, simple site installation -...
  • Scottish Procurement Customer Engagement Survey 2018 This survey

    Scottish Procurement Customer Engagement Survey 2018 This survey

    Scottish Procurement Customer Engagement Survey 2018. This survey was issued to gather customer feedback on the Procurement Journey and was issued via Survey Monkey. It was made available using various communication channels: