Download Atomic History Notes.notebook

Atomic History Notes.notebook
September 15, 2014
Signs of a Chemical Reaction
Physical Change - altering the form of a substance
without changing its chemical composition
Chemical Change - a change that alters the chemical
composition of a substance
Sep 5­7:45 AM
Chapter 3 - Elements, Atoms and Ions
Elements - a pure chemical substance consisting of one type
of atom; examples are Carbon, Hydrogen and Gold
Element symbols for the above elements are C, H and Au
- 1st letter is always capital, 2nd is lower case
- symbols are often derived from Greek and Latin
- Pb for lead comes from Latin word plumbum (liq. silver)
- Fe for iron comes from Latin word ferrum (sword)
Atoms - the smallest particle of elements that still retain
the property of the element
Sep 4­10:51 PM
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Atomic History Notes.notebook
September 15, 2014
Democritus - 460 - 370 BC
Often credited with being the father
of atomic theory.
Proposed that matter was made up of
tiny indivisible particles called atoms.
Democritus' theory was largely
ignored in his time and wasn't revived
until the early 1800's by John Dalton.
Sep 4­11:07 PM
Dalton devised an atomic theory (early
1800's) based on the following points:
1) Elements are composed of extremely
small and indivisible particles called
atoms.
2) Atoms of the same element are identical.
3) Atoms combine chemically in simple whole
number ratios, H2O is a 2:1 ratio of hydrogen and oxygen.
- A chemical compound is a distinct substance made up of
atoms or two or more elements (like water above)
4) Chemical reactions occur when atoms are separated, joined or
rearranged.
5) Atoms of one element are never changed into atoms or other
elements. (This is known as transmutation.)
Sep 4­11:15 PM
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Atomic History Notes.notebook
September 15, 2014
Atomic Structure
Electron - discovered by Thomson in 1897
- negatively charged ( -1 ) subatomic
particle
- almost 2000x smaller than H atom
Proton - discovered by Goldstein in 1887 (positive particles)
- Rutherford 1911 discovered nucleus and proton in 1917
- positively charge (+1) subatomic particle
- 1840X more massive than electron
Neutrons - discovered by Chadwick in 1932
- neutral charge
- approximately same mass as proton
Sep 4­11:28 PM
Rutherford's Gold Foil Experiment
Rutherford discovered the nucleus of the atom. Most alpha
particles (+) passed straight through, but a small percentage
were deflected. This indicated that the positive charge in an
atom most be concentrated in a small area, which he referred
to as the nucleus. If the Metrodome was an atom, the nucleus
would be about the size of a pea.
Sep 4­11:44 PM
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Atomic History Notes.notebook
September 15, 2014
History of Science Video
Sep 4­11:49 PM
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