Chapter 2 - Atoms, Molecules and Ions

Chapter 2 - Atoms, Molecules and Ions - Chapter 2: Atoms,...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Chapter 2: Chapter 2: Atoms, Molecules, and Ions Atoms, Molecules, and Ions Historical Origins of Chemistry c600 BCs Thales. Basic stuff of nature is water c550 BC Anaximenes. Primordial substance: air mid-500 BCs Pythagoras. 5 elements: earth, water, fire, air, ether mid-400 BCs Zeno. All matter is continuous c400 BC Democritus. Matter is made up of indivisible elements called atoma (or atomos) .
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 Atomic Theory of Matter Atomic Theory of Matter The theory that atoms are the fundamental building blocks of matter reemerged in the early 19th century by John Dalton. Described four postulates: Dalton Dalton ’s Postulates s Postulates 1.Each element is composed of extremely small particles called atoms . 2.All atoms of a given element are identical to one another in mass and other properties, but the atoms of one element are different from the atoms of all other elements. 3.Atoms of an element are not changed into atoms of a different element by chemical reactions; atoms are neither created nor destroyed in chemical reactions. 4.Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms .
Background image of page 2
3 Law of Constant Composition Law of Constant Composition •A l so known a s the law of definite proportions . • The elemental composition of a pure substance never varies. • Basis of Dalton’s Postulate #4 Joseph Proust Joseph Proust (1754 (1754 –1826) 1826) Law of Conservation of Mass (Matter) Law of Conservation of Mass (Matter) • The total mass of substances present at the end of a chemical process is the same as the mass of substances present before the process took place. • Basis of Dalton’s Postulate #3 • Can’t create matter in a chemical reaction! Antoine Laurent Lavoisier Lavoisier (1743 (1743 -1794) 1794) Discovery of Atomic Structure Discovery of Atomic Structure Mid 1800’s – scientists studied electrical discharge through partially evacuated tubes. Path of cathode rays deflected by presence of a magnet.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 Proposed in 1897 that Cathode Rays were actually particles (negatively charged) that we now know are electrons. J.J. Thomson J.J. Thomson (1856 -1940) 1940) Thompson measured the charge/mass ratio of the electron to be 1.76 × 10 8 coulombs/g. Millikan Oil Drop Experiment Millikan Oil Drop Experiment •Once the charge/mass ratio of the electron was known, determination of either the charge or the mass of an electron would yield the other. •Robert Millikan determined the charge on the electron in 1909, equal to 1.60 × 10 -19 C. •Mass could be calculated as 9.11 × 10 -28 g. MillikanOilDropExperiment.MOV
Background image of page 4
5 Radioactivity: The spontaneous emission of radiation by an atom. Also studied by Marie (1867-1934) and Pierre Curie (1857-1906). Discovered Po and Ra. Suggested that atoms of certain substances can disintegrate.
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 29

Chapter 2 - Atoms, Molecules and Ions - Chapter 2: Atoms,...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online