combinations of atoms chapter 4.2 page 87 organization of the periodic tableperiodic table each box...
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Organization of the Periodic Table
Each Box gives information about one element Name of element Atomic number
(number of protons)
Atomic Symbol Atomic Mass
Molecules The smallest unit of matter that
can exist by itself and retain all of a substances chemical properties
In a molecule two or more atoms are bonded together
Chemical Formulas A combination of letters and
numbers that shows the number of atoms of each element that are required to make a molecule of the compound
Chemical Equations Elements and compounds often
combine through chemical reactions
The reaction can be described in a formula
Photosynthesis formula
6H2O + 6CO2 -------> C6H12O6+ 6O2
Reactants on left products on right
The arrow is read yields
Balanced equations
An equation is balanced when the number of atoms on the right equals the number of atoms of the same element on the left
To balance a formula you use coefficients
Photosynthesis formula
6H2O + 6CO2 -------> C6H12O6+ 6O2
What is the blue arrow pointing to?What is the red arrow pointing to?
Book example Magnesium, Mg, reacts with oxygen, O2, to
form MgO, magnesium oxide
Write a balanced equation. We have two oxygen on the right so we will
need a number 2 on the left as a coefficient
2 Mg + O2 2MgO
Chemical Bonds The forces that hold together the atoms
in molecules are called
chemical bondsBonds form because of attraction
between opposite charges
Atoms can share or transfer valence electrons
Ions When an electron
is transferred from one atoms to another both atoms become charged
A charged particle like an atom or
molecule is an ion
Ionic Bonds Attractive force
between two oppositely charged ions that result from the transfer of electrons from one atom to another is called
An ionic bond
Na from the left wants to give away
Cl from the right wants to gain electrons
Ionic bonds form from atoms from opposite sides of the periodic table
Covalent Bonds A bond between
atoms that share electrons is called a
covalent bond
http://www.ithacasciencezone.com/chemzone/lessons/03bonding/mleebonding/covalent_bonds.htm
Polar Covalent Bonds Some atoms that are
covalently bonded do not equally share elections
A covalent bond with unequal attraction is called a polar covalent bond
Water is one example
Metallic Bonds Electrons flow
easily They are not
tightly bound
This explains the properties of metals
Physical Change
A change of matter from one form to another without a change in chemical properties Break Crush Melt
140
Change of State is a physical change An item can
change from solid to liquid to gas and still have the same chemical formula
140
Dissolving is a physical change
Example: dissolve salt in water You still have salt and water You could evaporate the water and get the salt back
Something that dissolves is soluble 140
Chemical Changes Form new substances with different
physical properties Can be detected
Fizz Smell Color Produce heat Produce a sound
Cannot be reversed by physical means
142
Mixtures A combination of two or more
substances that are not chemically combined
Two types: Heterogeneous--different Homogenous--same
Solution A homogenous
mixture of two or more substances that are uniformly dispersed
When a substance dissolves it goes into solution
Example salt in water
Compounds can be broken down by physical means
Carbonic acid in pop gives it fizz When the bottle is opened the
acid breaks down into carbon dioxide and water
Carbon dioxide escapes as bubbles
Mixtures can be physically separated
By Density Solubility Magnetism
Lab Activity Design an experiment to separate the
mixture in your sample—list the steps you will take below
Be sure to clean up your area when you are through
141
Test for the presence of CO2 and H2
A flaming splint is used to detect the presence of carbon dioxide or hydrogen gas CO2 extinguishes the flame H2
Creates a hydrogen burp
142
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