Atomic Structure and Periodicity. Chemistry Timeline #1. B.C. 400 B.C. Demokritos and Leucippos use the term "atomos”. 2000 years of Alchemy . 1500's Georg Bauer: systematic metallurgy Paracelsus: medicinal application of minerals. 1600's
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400 B.C. Demokritos and Leucipposuse the term "atomos”
2000 years of Alchemy
Robert Boyle:The Skeptical Chemist.Quantitative experimentation, identification of
Several changes have been made to Dalton’s theory.
Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties
Modern theory states:
Atoms of an element have a characteristic average mass which is unique to that element.
Atoms cannot be subdivided, created, or destroyed
Modern theory states:
Atoms cannot be subdivided, created, or destroyed in ordinary chemical reactions. However, these changes CAN occur in nuclear reactions!
The law of definite proportions states that a chemical compoundalways contains exactly the same proportion ofelementsby mass. An equivalent statement is the law of constant composition, which states that all samples of a given chemical compound have the same elemental composition by mass.
The Law of Multiple Proportions sometimes called “Dalton’s Law”states that if two elements form more than one compound between them, then the ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers.
In 1897, J.J. Thomson used a cathode ray tube to deduce the presence of a negatively charged particle.
Cathode ray tubes pass electricity through a gas that is contained at a very low pressure.
Thomson believed that the electrons were like plums embedded in a positively charged “pudding,” thus it was called the “plum pudding” model.
1909 – Robert Millikan determines the mass of the electron.
The oil drop apparatus
Mass of the electron is
9.109 x 10-31 kg
In the following pictures, there is a target hidden by a cloud. To figure out the shape of the target, we shot some beams into the cloud and recorded where the beams came out. Can you figure out the shape of the target?
“Like howitzer shells bouncing off of tissue paper!”
“q” is a particle called a “quark”
Protons and neutrons are NOT fundamental particles.
Protons are made of two “up” quarks and one “down” quark.
Neutrons are made of one “up” quark and two “down” quarks.
Quarks are held together
Isotopes are atoms of the same element having different masses due to varying numbers of neutrons.
Atomic number (Z) of an element is the number of protons in the nucleus of each atom of that element.
Mass number is the number of protons and neutrons in the nucleus of an isotope.
Mass # = p+ + n0
Lose 1 val. electron to form1+ions
Lose 2 val. electron to form2+ions
val. electrons or gains 4 val. electrons
Caution! C22- and C4- are both called carbide
val. electrons to form3-ions
val. electrons to form
Val. electron to form
Predicting Ionic Charges
Stable Noble gasesdo notform ions!
Groups 3 - 12:
have more than one possible oxidation state.
Iron(II) = Fe2+
Iron(III) = Fe3+
Groups 3 - 12:
have only one possible oxidation state.
Zinc = Zn2+
Silver = Ag+
Copper, Cu, is a relatively soft metal, and a very good electrical conductor.
Mercury, Hg, is the only metal that exists as a liquid at room temperature