The atom
Download
1 / 32

The Atom - PowerPoint PPT Presentation


  • 98 Views
  • Uploaded on

The Atom. From Philosophical Idea to Scientific Theory. Dalton’s Model of the Atom. Solid sphere: Solid indivisible sphere. Dalton’s Atomic Theory. 1. All matter is composed of extremely small particles called atoms.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'The Atom' - kera


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
The atom

The Atom

From Philosophical Idea to Scientific Theory


Dalton s model of the atom
Dalton’s Model of the Atom

  • Solid sphere:

    • Solid indivisible sphere


Dalton s atomic theory
Dalton’s Atomic Theory

  • 1. All matter is composed of extremely small particles called atoms.

  • 2. Atoms of a given element are identical in size, mass, and other properties… different elements have different properties

  • 3. Atoms cannot be subdivided, created, or destroyed


Dalton s atomic theory1
Dalton’s Atomic Theory

  • 4. Atoms of different elements combine in simple whole-number ratios to form chemical compounds

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


Modern atomic theory
Modern Atomic Theory

  • (what we believe about the atom today)

  • Keeps some of Dalton’s postulates but others have been disproved. Now we know:

    1. Atoms are divisible even into smaller particles

    2. A given element can have atoms with different masses


Cathode ray experiments
Cathode-ray experiments

  • Result of experiments between electricity and matter

  • Carried out in cathode ray tubes: Many of these experiments involved passing electric current through gases at low pressures


Cathode ray tube
CATHODE RAY TUBE

  • Picture – Label Parts


Cathode rays cont
CATHODE RAYS cont.

  • Experiments to Investigate Relationship between Energy and Matter

    • Procedure: Pass current from the cathode to the anode


1 st subatomic particle discovery
1st Subatomic Particle Discovery

  • RESULTS & HYPOTHESIS:

    Current passed through tube surface of the tube directly opposite the cathode glowed

    Hypothesized glow caused by a stream of particles, which they called a cathode ray


Experiments to test initial hypothesis
EXPERIMENTS TO TEST INITIAL HYPOTHESIS

MAIN RESULTS

  • 1. Object placed between cathode and opposite end of tube cast a shadow on the glass

  • 2. A paddle wheel placed on rails between the electrodes rolled along the rails from cathode toward anode.


Results continued
RESULTS CONTINUED

  • 3. Cathode rays were deflected by a magnetic field in the same manner as a wire carrying electric current, which was known to have a negative charge

  • 4. The rays were deflected away from a negatively charged object.


Hypothesis from the other experiments
HYPOTHESIS FROM THE OTHER EXPERIMENTS

  • The particles that compose cathode rays are negatively charged


Jj thomson
JJ Thomson

  • Supported Hypothesis (that cathode rays are negatively charged particles)

  • Measured the ratio of the charge of cathode-ray particles to their mass: found it was always the same Therefore concluded that all cathode rays are composed of identical negatively charged particles (called electrons)


Charge mass of electron
CHARGE & MASS OF ELECTRON

  • Thomson’s Experiment

    Showed that the electron has a very large charge for its tiny mass



Millikan
Millikan

  • Oil-drop Experiment


Robert a millikan s experiments 1909
ROBERT A. MILLIKAN’S EXPERIMENTS (1909)

  • He showed that the mass of the electron is about one two-thousandth (1/2000) the mass of the simplest type of hydrogen atom

  • More accurate experiments show the mass is actually 1/1837 the mass of H


Discovery of the atomic nucleus
DISCOVERY OF THE ATOMIC NUCLEUS

  • Rutherford’s Experiment (Draw Picture)


Startling results
STARTLING RESULTS

  • Expected the alpha particleds to pass through with only a slight deflection (assumed mass and charge were uniformly distributed throughout the atoms of the gold foil)

  • Mostly true but about 1 in 8000 was redirected back toward source


Rutherford s conclusions
RUTHERFORD’S CONCLUSIONS

  • 1. Rebounded alpha particles must have experienced some powerful force within the atom

  • 2. The force must occupy a very small amount of space in the atom. The atom must be mostly empty space


Rutherford s conclusions1
RUTHERFORD’S CONCLUSIONS

  • The force must be caused by a very densely packed bundle of matter with a positive electric charge.

  • He called this bundle of matter the nucleus.


Questions left to ponder
QUESTIONS LEFT TO PONDER

  • WHERE WERE THE ELECTRONS?

    Rutherford suggested that the electrons surrounded the nucleus like planets around the sun but did not know what kept the electrons in motion around the nucleus


Inside the atom part 2
INSIDE THE ATOM – PART 2

SUBATOMIC PARTICLES

ISOTOPES

AVERAGE ATOMIC WEIGHT


Subatomic particles
Subatomic particles

  • Protons (p+)

    • Nucleus

    • Determine the identity of the atom

    • Moseley’s organization of periodic table

  • Neutrons (n0)

    • Nucleus

  • Electrons (e-)

    • Most important in determining element’s properties


Using periodic table
Using Periodic Table

  • Periodic Table – Element information

Atomic #

# protons

Element

Symbol

Average Atomic

Weight (amu)


Using periodic table1
Using Periodic Table

  • Periodic Table – Element information

Atomic #

# protons

Element

Symbol

Average Atomic

Weight (amu)


Using periodic table2
Using Periodic Table

  • Subatomic particle values:

    • 1. Atomic #

    • 2. Atomic Weight

    • 3. Mass #



Isotopes
Isotopes

  • 1. Definition

    • Isotope: atoms of the same element with different numbers of neutrons

    • 2. Notation

      • Symbol

      • Hyphen


Average atomic weight
Average atomic weight

  • 1. Definition

    • Average atomic weight: weighted average of all naturally occurring isotopes of a given element

    • (Found on the periodic table)


Average atomic mass

Avg.

Atomic

Mass

Average atomic mass

  • 2. Formula:


Average atomic weight1
Average atomic weight

  • Example (Round to 2 decimal places)

    • Silver exists as 51.84% 107Ag and 48.16% 109Ag. The actual mass of 107Ag is 106.90509 amu and the actual mass of 109Ag is 108.90476 amu. What is the average atomic mass?