Download CHAPTER 2

The Chemical basis of Life

Anything that occupies ___________ and has
_________.
◦ Mass is commonly measured by how much something
weighs
◦ Can exist as:
 ____________
 ____________
 ____________
Element-
The simplest form of
matter that cannot be broken
into smaller substances by
natural means.
◦ Hydrogen, Oxygen, Carbon, and
Nitrogen make up 96% of the
matter in an animal’s body.
◦ Elements are referred to by a
____________ ______________and
are organized in the Periodic
Table of Elements.
GROUP
PERIOD 
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Major Elements
◦
◦
◦
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Oxygen(O)
Carbon(C)
Hydrogen (H)
Nitrogen (N)
Minor Elements
◦
◦
◦
◦
◦
◦
◦
Calcium (Ca)
Phosphorus(P)
Potassium(K)
Sulfur(S)
Sodium(Na)
Chlorine (Cl)
Magnesium (Mg)
◦
◦
◦
◦
◦
◦
◦
◦
◦
◦
◦
◦
◦
◦
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Silicone (Si)
Aluminum (Al)
Iron (Fe)*
Manganese (Mn)
Fluorine (F)
Vanadium (V)
Chromium (Cr)
Copper (Cu)*
Boron (B)
Cobalt (Co)
Zinc (Zn)*
Selenium (Se)
Molybdenum (Mo)
Tin (Sn)
Iodine (I)*
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
The ___________ unit of an element that
retains the unique properties of that element.
Composed of 3 subatomic particles:
◦ _________________
◦ _________________
◦ _________________

Protons and Neutrons are found in
the __________________.

Protons have a ______________charge.

Neutrons have __________ charge and
are considered neutral.

Each proton and each neutron has an
atomic mass of ~1.
◦ Together protons and neutrons determine
the atomic ____________ of the atom.
◦ The atomic _____________ of an element is
equal to the number of protons in that
element.
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Tiny particles that remain in constant motion
around the ________________.
So tiny that their mass does not contribute to the
atomic _____________ of the atom.
Electrons have a ____________charge.
The overall charge of an atom is neutral because
an atom has equal numbers of protons,
neutrons, and electrons.

The atomic number of an atom tells us how
many ______________ it has. This number cannot
change as it is what makes each element unique.
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
If an atom loses or gains an ______________, it
becomes positively or negatively charged,
thereby becoming an __________.
If an atom has equal numbers of protons and
electrons, but a different amount of neutrons, it
is called an ________________ of the element
Na atom
Na+ ion
11electrons,
11protons
10electrons,
11protons
e-

Shells are pathways around
the nucleus where
electrons orbit
◦ There are one or more shells
surrounding the nucleus,
depending on the # of
electrons.
◦ Only a certain number of
electrons can be on each
pathway/shell
◦ Electrons first fill the
innermost shell before moving
to the next shell
◦ First shell can contain
two electrons.
◦ Second shell can contain
eight electrons.
If the outermost shell is not
full, then an atom will be more
active in an attempt to fill it.



Atoms are stable when their
shells are full.
Atoms with incomplete
shells are constantly trying
to find electrons to
complete their outer shell.
Helium and Neon have full
electron shells so are
considered chemically
inactive/inert.


___________________- form when two or more
atoms are joined together by chemical bonds.
Molecule of the __________________-two or more
atoms of the same element are joined together.
 Example: Oxygen, O2

________________ -two or more atoms from
different elements are joined together.
 NaCl, CO2

Chemical bonding means that atoms are
_________________ or __________________ electrons.
◦ By doing this, each atom can be sure that its outermost
shell is full.
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Atoms are constantly trying to become more
stable.
Types of chemical bonds:
◦ _________________, _________________, _________________
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Bonds formed when atoms ______________ electrons.
Classification depends on how many electrons are
shared.
◦ single covalent bond: ______ electron is shared
◦ double covalent bond: ______ electrons are shared
◦ triple covalent bond: ______ electrons are shared

The shared electrons spend part of their time in
the electron shell of each of the atoms.
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
In some covalently bonded molecules, shared electrons may
spend more time near one atom than the other
Shared electrons in a water molecule spend more time near the
__________atom than __________ atoms
◦ Poles are created
 Gives molecule a slight _________ charge on H side of
molecule and slight _________charge on O side of molecule

Formed when electrons are _________________ from
one atom to another
 usually from an atom with one or two electrons in the outer
shell to an atom that needs one or two electrons to fill its
outer shell
◦ Transfer causes a ______ charge on the atom that gave up
the electron and a ____________ charge on the atom that
receives the electron.
◦ Since opposites attract, the two atoms “stick” together
through electrostatic attraction.

______________Ions with a net positive charge.
◦ Ca+, K+, Na+

_______________Ions with a net negative charge.
◦ Cl-, F-
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Ions are important in contraction of muscle fibers,
transmission of nerve impulses, and maintenance
of water balance.
________
bond between
hydrogen atoms already
______________ bonded in a
molecule to oppositely
______________ particles.
◦ (F,N,O)
Mostly
formed between
separate molecules, but can be
formed between parts of the
same large molecule (proteins
and DNA), which can alter the
molecule’s shape.

The formation and breaking of chemical bonds.

Require energy input or release of energy.

Chemical Equation- reaction is described in written
form.
◦ X+Y
→
◦ (reactants)
Z
(products)
◦ Arrow indicates direction of the reaction
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1. _______________ Reaction- new and more complex molecule
is made from multiple, simpler chemicals.
X + Y -> XY
O + O -> O2
2. ___________________ Reaction- single complex chemical is
broken down into multiple, simpler chemicals.
XY -> X + Y
2H2O -> 2H2 + O2
3. ________________ Reaction- certain atoms are exchanged
between molecules. Combination of synthesis and
decomposition reaction.
WX + YZ -> WZ + YX
NaCl + AgNO3 -> NaNO3 + AgCl