Chemistry 20
Intro
Mr McDonald
Welcome to Chemistry 20
• Review grade 10 concepts
• Review quiz
Resources
• Textbook or CD
• Nelson site
Matter
http://www.meta-synthesis.com/webbook/31_matter/matter2.jpg
SATP
• Standard Ambient Temperature and Pressure
– Temperature = 25 ᵒC
– Pressure = 100 kPa
Elements
• We have the periodic table of the elements
• There is order to the table based on
characteristics of the elements
– What are some of these characteristics?
Atoms
• Recall
• Mass number – total number of protons and neutrons
in the nucleus
• Atomic Number – number of protons
• Number of protons is constant but neutron and
electron numbers can be different
– Electrons: be in a full outer shell (if so called an ION)
– Neutrons: be the same as protons but if not it’s an isotope
Homework
• PG 2,3,4
• Book page 16 Q 2, 3, 5
• Element project
Electron shells
• For the first 20 elements the shells are:
– 2, 8, 8, (2)
• These are the only electrons that you need to know.
• But after the 20th element the shells can contain more
electrons, based on orbitals.
Various models of the atom
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•
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Dalton’s – “billiard ball” model
Thomson – “raisin bun” model
Rutherford – “Electron Cloud” model
Bohr – best model to date
Dalton’s Model
• Elements are made up of small particles called
atoms
• Atoms of the same element are equal in all
ways
• Atoms can not be sub-divided
• Atoms of different elements combine in whole
number ratios
• In chemical reactions – atoms combine,
rearrange
Thomson’s Model
• Atoms is a positive sphere and the electrons
are floating around inside
– Raisin bun.
http://upload.wikimedia.org/wikipedia/comm
ons/f/ff/Plum_pudding_atom.svg
Rutherford’s model
• Showed that all mass was within a small
region of the atom – nucleus
http://upload.wikimedia.org/wikipedia/commons/7/7d/Rutherfordsches_Atommodell.png
Bohr
• Makes an
extension of the
Rutherford model
that the electrons
are at certain
energy levels
from the nulceus