Chemistry Unit 2 Study Guide PDF

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Summary

main history of chemistry and info on scientists who changed the world of chemistry. also some isotope labelling....

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Chemistry Unit 2 Study Guide 1. John Dalton Theory: All matter is made of tiny particles called atoms Atoms of the same element are identical. Atoms of different elements are different. Atoms of different elements combine in whole number ratios to form compounds. Atoms of different elements are different therefore, have different masses because each element has a different atomic mass. J.J. Thompson (plum pudding)  Made an experiment by creating the cathode ray tube-vacuum tube that all air has been pumped out of and a limited amount of other gases are put into the tube.  Found the electron (negative)  Couldn’t find positive particle  Like plum pudding a bunch of positive stuff with the electrons able to be removed. Ernest Rutherford (gold foil experiment)  Believed in plum pudding but wanted to see how big an atom was.  Used radioactivity and alpha particles- positively charged pieces given off by uranium.  Shot them at gold foil. Bohr Model  Showed a center nucleus with rings of orbiting electrons. (KLMNOP)  K shell holds 2 electrons other shell holds 8  The most outer electrons are called valence electrons.  Each electron has energy. If one gets more energy it jumps one orbital up.  This energy will eventually decrease and the electron can go back to its original orbital. Wave mechanical model  Accepts orbital model however, redefines orbital as electron cloud.  Electron cloud- region where you might find an electron.  Uncertainty principle: it is impossible to know the exact momentum and position of electron at one time.    

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Subatomic Particles: Electron: negatively charged particles surrounding nucleus. -1 charge. Proton: positively charged particles in nucleus. +1 charge Neutron: no charge but same mass as a proton in nucleus. It is there for its mass nothing else. Atomic number = # of Protons # of protons = # of electrons in neutral atom Atomic mass = # of protons + # of neutron Isotopes-atoms of the same element that have a different number of neutrons. Therefore different mass number.

Naming isotopes: Name of element and mass number. Finding the number of neutrons in isotopes: atomic mass - # of protons. Measuring Atomic Mass:    

Unit measured it atomic mass unit. (AMU) Each isotope has its own atomic mass We get the average using percent abundance Decimal numbers on the periodic table.

Exited state:  

When an electron gains enough energy to move up an orbital and stay there until it goes back to its normal energy level. Ground state is the opposite.

The maximum number of electrons that can occupy an orbital: 2...