AP Biology
Chapter 2 Guided Reading Assignment
Name _________________________
This chapter is a review of basic chemistry – we will be going through this chapter very
quickly. If you have any problems – please see me before school for additional help.
1. Contrast the term element with compound.
Element is a substance that cannot be broken down to other substances by
chemical reactions, where a compound has two or different elements combined
in a fixed ratio
2. Label the diagram below and define the terms that you label.
Electron cloudArea around the
nucleus where
electrons are
likely to be
Electron- particle
with a negative
charge
Electron shellthe energy level
where electrons
are likely to be.
Neutron-a subatomic
particle with no charge
Proton- a
subatomic
particles with a
positive chage.
Nucleus- protons and
neutrons in the center of
the atom
3. Contrast the terms atomic mass and atomic number.
The atomic mass is the average mass of an atom (the number of protons and
neutrons) the atomic number is the number of protons.
4. What is the difference between the terms atomic mass and atomic weight?
Atomic mass is the average mass of all an elements isotopes while the atomic
weight is the weight of an isotope.
5. What is an isotope and what is “special” about radioactive isotopes?
An isotope is atom with a different atomic mass. A radioactive isotope has a
nucleus that decays spontaneously, giving off particles and energy
6. Explain how radioactive tracers are used in science?
Radioactive isotopes are used to label certain chemical substances. Therefore,
metabolic processes can be followed or substances can be located in an
organism
Page 1 of 3
7. Explain how the movement of electrons relates to the concept of potential energy
– use the diagram below to help answer the question.
The farther an electron is from the nucleus the more
energy it has. Just like the farther an object is from the
ground the more potential energy it has.
8. What determines interactions between atoms? Why are valence electrons
important?
The number of valence electrons determines interactions between atoms. The
chemical behavior of an atom depends on its valence electrons.
9. Define the following terms:
a. Chemical bond - an attraction between two atoms resulting from the
interaction of valence electrons
b. Covalent bond - the sharing electrons by two atoms
c. Single bond - the sharing of 1 pair of electrons between 2 atoms
d. Double bond - the sharing of 2 pair of electrons between 2 atoms
e. Valence - electrons in the outer most shell
f. Electronegativity – the strength of attraction an atom has for electrons
g. Nonpolar covalent bond - when electrons are shared equally by the atoms in
a molecule
h. Polar covalent bond – electrons are not shared equally by the atoms in a
molecule due to differences in electronegativity.
10. What is the difference between a structural and molecular formula?
the molecular formula writes the chemical symbol with subscripts while the
formula indicates bonds
11. How do ionic bonds compare with covalent bonds?
Covalent bonds are stronger than ionic bonds. Ionic bonds are formed by the
attraction of an anion and a cation. A covalent bond is formed by sharing valence
electrons.
Page 2 of 3
12. Compare and contrast hydrogen bonds and van der Waals interactions.
Hydrogen bonds are interactions between positive poles and negative poles of
polar molecules like water. Van der Waals interactions are between the positive
nucleus of one atom and the negative electron cloud of neighboring atoms.
13. Based on the reading, what is an example, in a living system, of how molecular
shape is critical?
Molecular shape determines the function of a molecule. If something changes the
shape of a molecule, it will no longer function properly.
14. Define a dynamic chemical equilibrium in terms of quantities of reactants and
products. This is a critical concept!
In a reversible chemical reaction the point at which the rate of the forward
reactions and reverse reactions are equal. The reactions are still occurring but
with no effect on the amount of reactants or products.
Page 3 of 3