Transcript Chemistry

Chemistry
A walk down memory
lane…
Or at least it should be
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?
Atoms – The smallest unit of matter
that cannot be broken down by
chemical means
*All matter consists of atoms
Nucleus
Electron Cloud
•Protons (+)
•Electrons (-)
•Neutrons (0)
* Nuclei can only be changed by fission or fusion! *
Electron Clouds
• Areas of probability
• Electrons do not really
travel in orbits like
planets
S orbital
– Bohr Model
• Electrons are in clouds
• The farther from the
nucleus, the easier an
p orbitals
e- is lost
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
Atomic Number
36
Kr
Krypton
83.80
Atomic Weight
Symbol
How do we figure out the number of
protons, neutrons, and electrons?
36
Kr
Krypton
83.80
Protons = atomic number = 36
Electrons = atomic number = 36
Neutrons = atomic weight – atomic
number = 84-36= 48
• 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
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!
•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
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
Lets put some atoms together!
• Compound – two or more atoms joined
together
• Molecule – two or more atoms share
electrons
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”
Metallic Bonds
• Electrons move from one atom to the next
• Forms between 2 metals
Hydrogen Bond
• Between 2 polar Partially
MOLECULES Negative
• Weak bond
• Positive and negative
charges attract much
like opposite poles of
a magnet
Partially
Positive
*This allows for adhesion, cohesion, and capillary action in water*
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
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