Chemistery 20 - qatarcanadianschool

Chemistry 20
Mr McDonald
Welcome to Chemistry 20
• Review grade 10 concepts
• Review quiz
• Textbook or CD
• Nelson site
• Standard Ambient Temperature and Pressure
– Temperature = 25 ᵒC
– Pressure = 100 kPa
• 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?
• 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
• 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
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 of the same element are equal in all
• Atoms can not be sub-divided
• Atoms of different elements combine in whole
number ratios
• In chemical reactions – atoms combine,
Thomson’s Model
• Atoms is a positive sphere and the electrons
are floating around inside
– Raisin bun.
Rutherford’s model
• Showed that all mass was within a small
region of the atom – nucleus
• Makes an
extension of the
Rutherford model
that the electrons
are at certain
energy levels
from the nulceus