Download Chemistry - Chapter 2 - WSCC Biology Tutoring

Exercise 2-1: Basic Chemistry
An atom is the smallest part of an element that still displays the properties of that element. An element
is what makes the three states of matter: solid, liquid, and gas. Matter is anything that has mass and
takes up space. The six main elements concerned in biology are Carbon, Hydrogen, Nitrogen, Oxygen,
Phosphorus, and Sulfer, also known as CHNOPS. These elements make up about 95% of the body weight
of all organisms.
The Atomic Theory states that elements consist of atoms. This theory was founded by John Dalton, an
English scientist. An element and its atoms share the same name which is abbreviated by one or two
letters. The names are either English or Latin. H stands for Hydrogen, Na stands for Sodium (Natrium in
Latin).
Atoms have three basic parts: protons, neutrons, and electrons. Protons have a positive charge, a mass
of one AMU or atomic mass unit, and are found in the nucleus of an atom. Neutrons have no charge, a
mass of one AMU, and are also found in the nucleus of an atom. Electrons have a negative charge, no
mass, and are found orbiting the nucleus of an atom in rings called electron shells.
Directions: Labe the electrons, protons, neutrons.
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The atomic number of an atom is determined by the number of protons in an atom. The atomic mass of
an atom is the number of protons plus the number of neutrons in an atoms nucleus. The number of
protons is equal to the number of electrons.
Atomic #
Atomic Mass
Isotopes are atoms of the same element that differ in the number of neutrons. (Same atomic number,
different atomic mass) They have the same number of protons but different atomic masses.
The Bohr Model is used to show the location of electrons around the nucleus of an atom. The first
energy shell can hold up to 2 electrons. The second and third can hold up to 8 electrons. This is known as
the octet rule. The outer energy shell is known as the valence shell.
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I.
Protons, Neutrons, and Electrons and the Bohr model
Directions-give the number of protons, electrons, and neutrons and draw a bohr model
representing the following elements.
1) Hydrogen
2) Oxygen
3) Carbon
4) Nitrogen
5) Phosphorus
6) Sulfer
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II.
Isotopes
Isotopes are atoms of the same element that differ in the number of neutrons. In other words they have
the same atomic #, the number of protons, but have different atomic masses, the number of protons
plus neutrons. Isotopes are used today in the medical field. Below are some common isotopes of atoms,
give the number of protons and number of neutrons in the nucleus, the atomic mass, and draw a model
of the atoms nucleus.
1. Boron-11
a. Proton #b. Neutron #c. Atomic Massd. Nucleus-
2. Chlorine-37
a. Proton #b. Neutron #c. Atomic Massd. Nucleus-
3. Oxygen-17
a. Proton #b. Neutron #c. Atomic Massd. Nucleus-
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The pH Scale
The pH scale is used to determine how acidic or how basic (alkalinity) a substance is. Acids are
substances that dissociate in water and release hydrogen ions (H+). Depending on how fully the acid
dissociates determines how acidic the substance is. Bases are substances that either take up H+ or
release hydroxide ions (OH-). A buffer keeps the pH of substances in normal range.
*0-2=Very Acidic; 3-6=Acidic; 7=Neutral; 8-11=Basic; 12-14=Very Basic
Directions: Determine whether the following items are either acidic, basic, very acidic, very basic, or neutral.
1.
2.
3.
4.
5.
6.
7.
8.
Water=
Urine=
Bleach=
Tomato Juice=
Black Coffee=
Battery Acid=
Ammonia=
Toothpaste=
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Compounds and Molecules
A compound is two or more elements that are bonded together. A molecule is the smallest part of a
compound that still has the properties of that compound. There are two types of bonds that bring
elements together to form compounds: covalent and ionic bonds. A covalent bond is when two atoms
share electrons so that their valence shell is full. Covalent bonds are often found in nature and in living
things. There are two types of covalent bonds: polar and nonpolar. Polar covalent bonds are formed
when the electrons are not shared equally. This results in the atoms of the compound becoming
charged. In nonpolar covalent bonds the electrons are shared equally and a charge is not formed. Ionic
bonds form when an atom looses or gains an electron therefore giving that atom a charge. It is looses an
electron then it will have a positive charge because there are more protons than neutrons. If it gains an
electron it will have a negative charge because it has more electrons than protons. A charged atom is
known as an ion.
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