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Mr Yi Midterm questions


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Greek Philosopher - all matter is actualy composed of tiny indivisible particles called ATAMOS (450 BC)
Tried to turn ordinary metals into gold (400 BC)
Antoine lavoisier
Law of conservation of matter - matter is neither created nor destroyed in a chemical reaction (1783)
Joseph Louis Proust
Law of constant composition - Compoinds always contain the same elements in the same proportion by mass - eg. Water is always 88.9% oxygen and 11.1% hydrogen.
John Dalton
Atomic theory of matter
-Each element is composed of extremly small particles called atoms
-All atoms of a given element are identical, but they differ from those of any other element (false)
-Atoms are neither created nor destroyed in any chemical reaction
-A given compound always has the same relative numbers of kinds of atoms.
Michael Faraday
Atomic structure is related to electricity (1839)
William Crooks
-Developed the cathode ray tube (crookes tube)
-Performed experiments involving the flow of electric current through glass... Gasses sealed in glass tubes with metal discs at each end...Electrodes are conected to a high voltage source of electricity...a stream of charged particles flows from the cathode(-) to the anode(+)
J.J. Tompson
magnetic and electric fields deflected the path of the cathode ray tube.
-DISCOVERED negativly charged particles named ELECTRONS
-Plum pudding model - negativly charged electrons floating in a positive material.
Henri Bacquerel
Natural Radiation from uranium ores (Radioactivity)
Ernest Rutherford
3 types of radiation
-Alpha (Positive)
-Beta (Negative)
-Gamma (Neutral)most dangerous.
---Gold Foil experiment---
aimed alpha(+) particles thin gold paper..Expected alpha would pass straight through..small amound deflected (1/8000)
-concluded all atoms have a + charge in a very small core -((NUCLEUS))- atom is mostly empty space
Error Formula
|measured value-accepted value|
-PERCENT error
(Absolute error/accepted value) X100
SigFigs In addition/subtraction
answer has same number of DECIMAL PLACES as the measurement with the least number of decimal places - eg. 97.542-22.44=75.102 = 75.10
SigFigs In Multiplication/Division
Answer has same number of SIGFIGS as the measurement with teh least number of sigfigs -eg. 2.5674cm x3.5cm x3.54cm =32cm^3
When an atom loses or gains one or more electrons it acquires a net electrical charge called and anion - Charge = #protons -#electrons
Atoms of the same element that contain different numbers of neutrons
Hydrogen 1p+ 0 n0
Deutrerium 1p+ 1 n0
Tritium 1p+ 2 n0

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