Lecture 2 Chem 102

Lecture 2 Chem 102 - Chapter 2 Atoms, Molecules and Ions...

Info iconThis preview shows pages 1–13. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 2 Atoms, Molecules and Ions
Background image of page 1

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

View Full DocumentRight Arrow Icon
1. Law of conservation of mass (Lavoisier): Mass is neither created nor destroyed. 2. Law of definite proportion (Proust): A given compound always contains exactly the same proportion of elements by mass. 3. Law of multiple proportions (Dalton): When two elements form a series of compounds, the ratios of the masses of the second element that combine with 1 gram of the first element can always be reduced to small whole numbers. Fundamental Chemical Laws
Background image of page 2
Dalton (1808) 1. Each element is made up of tiny particles called atoms. 2. The atoms of a given element are identical. The atoms of different elements are different in some fundamental way. Early Atomic Theory
Background image of page 3

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

View Full DocumentRight Arrow Icon
3. Chemical compounds are formed when atoms of different elements combine with each other. A given compound always has the same relative numbers and types of atoms . 4. Chemical reactions involve reorganization of the atoms . The atoms themselves are not changed in a chemical reaction. But there are changes in the way they are bound together. Early Atomic Theory
Background image of page 4
J. J. Thomson (1898—1903) Cathode-Ray Tube Postulated the existence of electrons using cathode-ray tubes . The atom must also contain positive particles that balance exactly the negative charge carried by particles that we now call electrons. Plum Pudding Model
Background image of page 5

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

View Full DocumentRight Arrow Icon
Explained the nuclear atom . Atom has a dense center of positive charge called the nucleus. Electrons travel around the nucleus at a relatively large distance. Ernest Rutherford (1911)
Background image of page 6
The atom contains: Nucleus Electrons outside the nucleus; (-) charged. The nucleus contains: Protons – (+) charged; equal in magnitude to the electron’s negative charge. Neutrons – no charge; virtually same mass as a proton. Modern View of Atomic Structure
Background image of page 7

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

View Full DocumentRight Arrow Icon
Nucleus is very small Accounts for almost all of the mass of an atom High density Density = Mass/Volume The Size of an Atom The radius (electron) >10 5 x radius (nucleus)
Background image of page 8
The Size of an Atom Mass of an atom is due to its Protons and Neutrons Size of an atom is due to its Electrons Mass of proton = mass of neutron = 1.66 x 10 -24 g Mass of electron = 9.109 x 10 -28 g Electron <<< Proton, Neutron
Background image of page 9

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

View Full DocumentRight Arrow Icon
The Charge of an Atom An atom is neutral It has no net charge Number of electrons = number of protons Proton: +1 Neutron: no charge Electron: -1
Background image of page 10
Elements and Compounds A Compound 2 or more specific atoms (elements) combined in a fixed ratio NaCl: Sodium and Chloride An Element Made up of only 1 type of atom Carbon
Background image of page 11

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

View Full DocumentRight Arrow Icon
Why are atoms different? What makes them different? How are they different? Carbon, Sodium and Chloride All comprised of protons, neutrons and electrons Yet they are different If all atoms are composed of these same components, why do different atoms have different chemical properties ?
Background image of page 12
Image of page 13
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 78

Lecture 2 Chem 102 - Chapter 2 Atoms, Molecules and Ions...

This preview shows document pages 1 - 13. Sign up to view the full document.

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