Name________________________________
Biochemistry
Date_____________________
Homework
A. BASICS OF CHEMISTRY. The cell is a complex "chemical factory". It is made up of atoms,
elements, compounds, and molecules. The chemical processes of the organism take place inside the
organism's cells. To understand life processes you need a basic knowledge of chemistry.
1. The cell is a complex __________ factory.
2. Where do the chemical processes of the organism take place?
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B. THE ATOM. Living and nonliving things are made up of tiny units called atoms. The center core is
called the nucleus. The nucleus is made up of particles called protons and neutrons. Protons have a
positive charge (+1) and neutrons have no electrical charge (0). Negatively particles, called electrons
(-1), revolve around the nucleus at different distances from the nucleus. The electrons move in paths
called shells or energy levels. Atoms have the same number of electron and protons; therefore, they are
electrically neutral (have no electrical charge).
1. Living things are composed of tiny units called _________.
2. The nucleus is the _______________ of an atom.
3. Complete the following chart comparing electrons, proton, and neutrons.
PARTICLE
CHARGE
LOCATION
4. Why are atoms electrically neutral? _________________________________________________
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C. ELEMENTS. There are about 100 different kinds of atoms known to scientists today. A substance
made up entirely of one kind of atom is called an element. Ninety-two elements occur naturally and the
others were made in a laboratory. Elements differ from one another in their proton, neutron, and
electron number. An element cannot be broken down into any other substance or matter. For example,
pure silver is an element. It is made up only of silver atoms. When you break down a silver atom, you
get electrons, protons, and neutrons.
Electrons
1p
6p
6n
8p
8n
Carbon
Oxygen
7p
7n
Energy Levels
Hydrogen
Nitrogen
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Each element is represented by a symbol made up of one or two letters. The symbols of some of the
most common elements are:
Element
Carbon
Hydrogen
Oxygen
Nitrogen
Sulfur
Phosphorus
Magnesium
Symbol
C
H
O
N
S
P
MG
Element
Iodine
Iron
Calcium
Sodium
Chlorine
Potassium
Zinc
Symbol
I
Fe
Ca
Na
Cl
K
Zn
1. A substance made up entirely of one kind of atom is called an ______________.
2. A symbol represents an ___________________________.
3. How do elements differ from one another? ___________________________________________
_________________________________________________________________________________
4. In the space below, draw and label the atomic models of carbon and oxygen.
5. Complete the following table.
Element
Phosphorus
Symbol
Element
Calcium
O
Mg
Iron
Nitrogen
K
Symbol
S
H
Carbon
Carbon
Chlorine
D. COMPOUNDS. A compound is formed when two or more elements combine chemically. The
properties (characteristics) of compounds are quite different from the properties of the elements of
which they are composed. For example, table sugar is made up of the elements carbon, hydrogen, and
oxygen. Carbon is a black solid, and hydrogen and oxygen are colorless gases. However when they
combine chemically they form a white granular substance.
Elements combine to form compounds by a process called chemical bonding. The formation of a
chemical bond involves either the transfer of electrons from one atom to another, or the sharing of
electrons between atoms. For example, when sodium combines with chlorine, one molecule of sodium
chloride (table salt) is formed. During this process, the sodium atom loses (transfers) an electron to the
chlorine atom.
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1. What is a compound? ____________________________________________________________
2. Compounds are made up of __________________________.
3. How do elements combine to form compounds? _______________________________________
______________________________________________________________________________
______________________________________________________________________________
E. MOLECULES. The smallest particle of an element or compound capable of independent motion is a
molecule. A molecule of a particular compound is made up of definite numbers and kinds of atoms
bonded (joined) together. A molecule of water contains two hydrogen atoms and one oxygen atom
bonded together. Two atoms of hydrogen bonded together form a molecule of hydrogen.
1. Molecules are defined as _________________________________________________________
2. A molecule of water is composed of ________________________________ and
________________________ bonded together.
F. IONS. An ion is an atom that has gained or lost an electron. Ions are formed during chemical bonding
that involves the transfer of electrons. When electrons are transferred from one atom to another, both
atoms become electrically charged. The atom that loses electrons becomes positively charged. The
atom that gains electrons becomes negatively charged. The ions with opposite electrical charges are
attracted to one another. A chemical bond formed when atoms lose or gain electrons is called an ionic
bond.
In the formation of sodium chloride, the sodium atom lost an electron and became a sodium ion with an
electrical charge of +1. The chlorine atom gained an electron and become a chloride ion with a charge
of -1.
1. What is an ion? _________________________________________________________________
______________________________________________________________________________
2. When is an ionic bond formed? ____________________________________________________
G. COVALENT BONDS. Covalent bonds are formed when atoms produce compounds by sharing
electrons. A simple example is the making of hydrogen gas. One molecule of hydrogen gas is formed
when two hydrogen atoms join by sharing electrons.
1. Covalent bonds are formed when atoms _____________ electrons.
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