Ch. 2: Chemistry Basics – Notes
Date:________
ATOMS
• The center of the atom is called the
.
• It contains:
• ____________________ (mass of 1, + charge)
• ____________________ (mass of 1, no charge)
• Circling the nucleus in orbitals (or shells) are ________________ (mass 0, -charge)
• The atomic number is the
• The number of protons and electrons should be equal so that the atom is neutral.
• The atomic mass is the
ELEMENTS
• Elements are the basic chemical units that cannot by broken apart by typical chemical
processes.
• There are
naturally occurring elements. Four of these are found in all living
things:
,
,
,
and
.
ISOTOPES
• Elements with the same atomic number but different
are called
isotopes. Isotopes basically have the same number of protons but a different number of
.
• Some of the larger elements have isotopes that are unstable. These isotopes are
considered radioactive.
 Isotopes of the same element behave the same way chemically. That means that
your body can not tell the difference between two isotopes.
o Radioactive isotopes have many functions in science:
 They can function as “markers.”
 Radioactive elements are also used in medical procedures.
 Radiation can also be used as a treatment.
o Long-term exposure or exposure to high-energy radiation can cause
diseases such as cancer.
COMPOUNDS
• Compounds contain two or more atoms in a
.
• Different combinations of atoms determine the unique
properties of each compound.
• The properties of elements depend on their
.
• Specifically - The chemical reactivity of an
atom depends on the number of electrons
in the outer electron shell of the atom.
(
)
CHEMICAL BONDS
• There are two major chemical bonds used by elements
to build compounds: covalent bonds & ionic bonds.
• NOTE: In each of the bond types, two rules are satisfied:
(1) the resulting compound is electrically neutral,
(2) outer electron orbits are filled.
•
Ionic bonds
___
• Ions are atoms that have lost or gained electrons.
• When an atom loses an electron, it becomes a
ion.
• When an atom gains an electron, it becomes a
ion.
• Two or more ions can come together to form a molecule due to the attraction of
opposite charges that result from the transfer of electrons.
•
Covalent bonds join
.
• Each atom in a molecule composed of covalent bonds shares electrons in its outer
shell with the other atom(s) in the molecule.
• Examples: H2, O2, CH4, and H2O .
POLARITY
• Remember that
occur between atoms that share electrons.
• There are two types of covalent bonds:
•
•
• While nonpolar molecules
the electrons equally, polar molecules do
not…
• This results in one part of the molecule being slightly positive and another part
being slightly negative.
WATER
•
•
•
•
•
is a polar molecule.
The oxygen in water is
the two hydrogen atoms are
, and
.
Hydrogen Bonds are weak bonds that form between slightly + and – molecules…
They form BETWEEN water molecules, in our
, and in proteins…
Because of Hydrogen Bonds
• Water is cohesive.
• Cohesion is the tendency of water molecules
to
.
• Cohesion on the surface of water is called
surface tension!
• Water is
.
• Adhesion is the attraction between molecules
of different substances.
MIXTURES & PH
• Water is often found mixed with other molecules and elements.
• There are two types of mixtures:
•
•
• A
is a homogeneous mixture…
• In a solution the atoms or molecules of the different substances are equally
distributed.
• Examples:
•
Solutions are always composed to two parts, a solute and a solvent.
• The solute dissolves in the solvent.
• Water is called the universal solvent because so many things dissolve in it.
•
A
•
•
•
is a heterogeneous mixture…
In a suspension the atoms or molecules that are mixed together do not spread
out equally.
Examples:
Mixtures are important to living things – one thing you need to know about mixtures is
that they always have a pH.
•
•
pH Stands For
pH measures whether a mixture is an ACID or BASE.
…
•
As water mixes with other atoms it breaks apart… (or ionizes)
H2O
OH- and H+
• OH (hydroxide ions)
• H+ (hydrogen ions)
•
When water mixes with a base a lot of
OH- (hydroxide ions) are produced.
• Bases have a pH
than 7 on the scale.
•
When water mixes with an acid a lot of
H+ (hydrogen ions) are produced.
• Acids have a pH
than 7.
CHEMICAL RXNS
•
Chemical reactions are reactions that change the composition of matter.
o The general form of a chemical reaction is:
•
•
The reactants are the starting material, and the products are the result.
Label the reactants and products in the reaction below:
Sodium + Chlorine
Sodium Chloride (Salt)
•
Notice that the number of atoms on each side of the equations are
• These are
equations!
Note how different the reactants look from the product…..
Chemical reaction of Hydrogen (g) and Oxygen (g) to make Water (l)…..
.