Atomic structure
This presentation is the property of its rightful owner.
Sponsored Links
1 / 18

Atomic Structure PowerPoint PPT Presentation


  • 56 Views
  • Uploaded on
  • Presentation posted in: General

Atomic Structure. Atoms, Elements & Isotopes. proton, neutron and electron. isotopes exist. Dalton’s Atomic Theory. Four postulates (1808)... All elements are composed of tiny, indivisible particles called ‘atoms’. Atoms of the same element are identical... each element is unique

Download Presentation

Atomic Structure

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


Atomic structure

Atomic Structure

Atoms, Elements & Isotopes


Atomic structure

proton, neutron and electron

isotopes exist

Dalton’s Atomic Theory

  • Four postulates (1808)...

  • All elements are composed of tiny, indivisible particles called ‘atoms’.

  • Atoms of the same element are identical... each element is unique

  • Atoms of different elements can physically mix or chemically combine (compounds).

  • Chemical reactions occur when atoms are separated, joined, or rearranged.

    • Much of this theory is still accepted, ….. with 2 exceptions.


Atomic structure

Atomic Scientists

  • J. J. Thomson discovered electrons (e-) in 1897.

  • He passed an electric current through a glass tube filled with gas.

  • He discovered that a beam of negative charges traveled from the cathode (-) to the anode (+).


Atomic structure

Atomic Scientists

  • E. Goldstein discovered positive particles in atoms in 1886.

  • He observed rays traveling in the opposite direction of cathode rays.

  • These particles were termed ‘ protons’ (p+) by Ernest Rutherford in 1920.

  • James Chaddwick discovered neutrons (n0) in 1932.

    • His discovery was based on the fact that different atoms’ atomic mass and atomic # (# of protons) were not adding up.


Atomic structure

Atomic Scientists

  • Robert Millikan furthered Thomson’s work by describing the electron more in depth

  • all e- carry exactly one unit of negative charge.

  • mass of an e- is 1/1840 the mass of a hydrogen atom (p+).


Atomic structure

The Bohr-Rutherford Model

  • Ernest Rutherford conducted the famous ‘gold foil experiment’ (1911) which concluded that:

    • 1. atoms are mostly space. (football arena)

    • 2. atoms have a solid nucleus at the centerwhich contains most of the mass

  • This overturned the accepted ‘plum pudding model’ of the time.


Atomic structure

The Bohr-Rutherford Model

  • The Gold Foil Experiment...

  • Stats...

    • 98% of particles went straight through (expected)

    • 2% of particles deflected at large angles

    • 0.01% of particles deflected straight back (canon balls & tissue!)


Atomic structure

The Bohr-Rutherford Model

  • After Rutherford’s findings, Niels Bohr further explained the atom by concentrating on the e- (1913).

  • Why don’t the (-) e- fall into the (+) nucleus?

  • Bohr proposed that the e- travel on concentric orbits around the nucleus.

    • Each orbit has a fixed energy (energy level) and e- do not lose energy.

  • The progression of the atom...

Plum Pudding

Rutherford

Quantum

Rutherford-Bohr


Subatomic particles

Subatomic Particles


Atomic structure

19

K

Potassium

39.098

Characteristics of Elements

Atomic Number

Element Symbol

Element Name

Atomic Mass


Atomic structure

Characteristics of Elements

  • Atomic Number : Number of p+ in an atom

    • identifies element (change atomic # = change of element).

      • # p+ = # e- in neutral atom

      • (+) charge = less e- than p+

      • (-) charge = more e- than p+

  • Atomic mass: (a.k.a. Mass Number)

    • mass of the nucleus

      • p+ + n0

      • units are a.m.u. (atomic mass unit)


Atomic structure

X

#

element symbol

#

X

#

Atomic Symbols

  • There are two ways to represent elements:

  • Symbol Form:

OR

atomic mass

atomic #

(# of p+)

element symbol

atomic mass

  • Shorthand Form: name of element followed by atomicmass.

  • Ex...

    • Aluminum - 27

    • Nitrogen – 14

    • Carbon – 14

  • You can find mass number, atomic number, number of n0, and number of e- with either notation!


Atomic structure

X

#

element symbol

#

X

#

Atomic Symbols

  • There are two ways to represent elements:

  • Symbol Form:

atomic mass

atomic #

(# of p+)

element symbol

atomic mass

OR

  • Shorthand Form:

  • name of element followed by atomic mass.

    • Ex...Aluminum – 27

  • Find the following elements on the Periodic Table:Beryllium, Copper, Sulfur, Neonand write them in both notations.


  • Atomic structure

    atomic mass

    X

    #

    element symbol

    atomic #

    #

    (# of p+)

    • Now find for each element the:

    • atomic mass

    • atomic number

    • # of p+ (same as atomic#)

    • # of n0 (mass# - atomic#)

    • # of e- (same as # of protons)

    Atomic Symbols

    • Using the symbol form for neutral elements:

    • Symbol Form:

    • Ex...

    1. Beryllium-

    2. Copper -

    3. Sulfur-

    4. Neon -


    Atomic calculations

    Atomic Calculations

    • All mass of the atom is in the nucleus.

      • only p+ and n0 are in the nucleus.

      • if you know the mass of any atom, you can find the # of n0.

      • if you know the # of n0 and the # of p+, you can find the mass.

        • Ex...electrical charge on atom

          Manganese - 55

    P

    +1

    31

    15


    Atomic structure

    Isotopes

    Neon - 20

    X

    +3

    X

    X

    -1

    22

    22

    25

    Fluorine - 20

    12

    10

    10

    Neon - 22

    • Isotopes: atoms of the same element with different atomic masses.

      • - different # of n0 !!!

        • Three isotopes of Carbon:

        • Carbon - 12 (6p+, 6n0) element of life

        • Carbon - 13 (6p+, 7n0) extremely rare

        • Carbon - 14 (6p+, 8n0) radioactive…carbon dating

      • Note: atomic # will NEVERchange in isotopes… only mass and # of n0 do!

      • Which of the following are isotopes of the same element?


    Atomic structure

    Average Mass of Isotopes

    • Isotopes are naturally occurring.

    • The mass # of an element (periodic table) is the weighted avg. of allisotopes that exist in nature.

      • - abundance of isotope is just as important as mass!

    • Ex...

      • Natural copper (Cu) consists of 2 isotopes …

      • Copper - 63 (mass = 62 .930 g/mole) @ 69%

      • Copper - 65 (mass = 64 .930 g/mole) @ 31%

    • To calculate avg. mass...

      • Step 1 : mass x abundance for each isotope

      • Step 2 :add the two values from step 1 together

      • 62 .93 x .69 = 43.42 43.42

      • 64 .93 x .31 = 20.13+ 20.13

    63.55 g/mole


    Atomic structure

    Average Mass of Isotopes

    • The average mass of an element is closest to the isotope that is mostplentiful in nature.

    • Ex...

      • Three isotopes of Oxygen:

        • Oxygen - 16 99 . 759%

        • Oxygen - 17 0.037%

        • Oxygen - 18 0.204%

  • The avg. mass (from P.T.) is closest to 16, therefore, Oxygen-16 is the isotope that is most abundant in nature.


  • Login