Download - Chemistry
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Chemistry
A walk down memory lane…
Or at least it should be
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If you can cook, you can do chemistry!
•The ingredients = reactants
•The cake/ cookies = product
•You only get out what you put in (Conservation of mass)
•Your products do not have the same properties as the reactants
•Does a cake taste the same as raw eggs, flour, etc?
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Atoms – The smallest unit of matter that cannot be broken down by
chemical means*All matter consists of atoms
Nucleus
•Protons (+)
•Neutrons (0)
Electron Cloud
•Electrons (-)
* Nuclei can only be changed by fission or fusion! *
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Electron Clouds
• Areas of probability• Electrons do not really
travel in orbits like planets– Bohr Model
• Electrons are in clouds• The farther from the
nucleus, the easier an e- is lost
S orbital
p orbitals
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Elements: a pure substance made of only one kind of atom
•Each element:
• Has a different number of protons
•Has a symbol (one or two letters)
•Organized on the periodic table
36
Kr
Krypton
83.80
Symbol
Atomic Number
Atomic Weight
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How do we figure out the number of protons, neutrons, and electrons?
• Atomic Number = the number of protons which = the number of electrons
• Atomic Weight = the total mass of the atom. Comes from the combination of protons and neutrons
36
Kr
Krypton
83.80
Protons = atomic number = 36
Electrons = atomic number = 36
Neutrons = atomic weight – atomic number = 84-36= 48
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Isotopes: atoms of the same element that have the same number of protons, but a
different number of neutrons
• Some isotopes are stable
• Some break apart and release energy (fission)
This is the reason why atomic weights are NOT whole numbers!
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•Organized by properties: Periodicity
•Period – horizontal rows
•Group – Vertical column
•Valence electrons – outermost e-, involved in bonding, same as the group number for the main block elements
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Patterns in the Periodic Table
• Diameter decreases as you move along the row from left to right
• Diameter increases as you move down the column
• Each column reacts similarly, because they have the same number of valence electrons
• Metals are on the left and nonmetals on the right
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Lets put some atoms together!
• Compound – two or more atoms joined together
• Molecule – two or more atoms share electrons
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Types of Chemical Bonds• Ionic
– Electrons are transferred– Makes ions when dissolved – Forms between a metal and a nonmetal
• Covalent– Electrons are shared– Forms between 2 nonmetals– Polar: e- are NOT equally shared– Non-polar: e- ARE equally shared* Don’t forget: “Like dissolves like”
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Metallic Bonds
• Electrons move from one atom to the next
• Forms between 2 metals
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Hydrogen Bond
• Between 2 polar MOLECULES
• Weak bond• Positive and negative
charges attract much like opposite poles of a magnet
Partially Negative
Partially Positive
*This allows for adhesion, cohesion, and capillary action in water*
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Balancing Chemical Formulas
• Step 1: determine the charge of the ion each element will form
• Step 2: Write the metal first, the nonmetal second
• Step 3: the charge of one atom is the subscript of the other
Mg2+ Cl-
MgCl2
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Polyatomic Ions
• “ion with many atoms”• The atoms in the polyatomic react as if they are
one atom – they do not rearrange• Written with parentheses around them if more
than one polyatomic is in the compound
• Mg(OH)2