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 * AP Biology** **Name _**
 * Chapter 2 Guided Reading Assignment **

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 compound. An element is a molecule made of a single type of atom that can't be broken down while a compound is a molecule that's made of two or more different elements.



2. Label the diagram below and define the terms that you label. a) Electron Cloud: Represents the 2 electrons as #|a cloud of negative charge Nucleus: Dense core in the middle of the atom made of neurons & protons
 * [[image:DIAGRAM.JPG width="488" height="353"]] ||
 * chem_chapter_2_Q_2_image.jpg ||

b) Electrons: Negatively charged particles that #|make up an atom Neutrons: Particles no charge.  Protons: Positively charged particles  Nucleus: Dense core in the middle of the atom made of neurons & protons

3. Contrast the terms atomic mass and atomic number. Atomic number is the number of protons and also the amount of electrons that an element has in its nucleus, as there are an equal number of protons and electrons in an element. Writing a subscript on the left of the atom's symbol shows atomic number. Atomic mass is the total mass of an atom that is measured in daltons.



4. What is the difference between the terms atomic mass and atomic weight? Atomic mass is the mass of the atom of that element, and atomic weight is the weight of that element in its natural state. For example, Hydrogen is a gas in its natural state so weighing one hydrogen would give you the atomic weight. [|Atomic Mass and weight]

5. What is an isotope and what is “special” about radioactive isotopes? An isotope has more neutrons than other atoms, and a radioactive isotope has a nucleus that decays spontaneously giving off particles and energy. [|Redioactive Isotopes on the Periodic Table]

6. Explain how radioactive tracers are used in science? They are used to follow atoms through #|metabolism. Radioactive isotopes are detected the same way that nonradioactive isotopes of the same element are by a cell. However, the radioactive tracers can easily be detected.

7. Explain how the movement of electrons relates to the concept of potential energy – use the diagram below to help answer the question.

The ball on the steps can not rest in between steps while falling, only when it comes in contact with a step. The picture shows that an electron can move from one level to another only if energy is gained or lost, ,just as the ball shows on the steps. The ball represents an electron and the steps represent the different energy levels of an atom. ||
 * [[image:bealbio/chem_chapter_2_Q_7_image.jpg caption="chem_chapter_2_Q_7_image.jpg"]] ||
 * The potential energy is shown above by the orange and yellow arrows.

8. What determines interactions between atoms? Why are valence electrons important? The chemical behavior of an atom depends mostly on the number of electrons in its outermost shell. Valance electrons contribute in sharing and making bonds. They donate or transfer between atoms. They also accept electron to from various bonds and pairs.



9. Define the following terms: a. Chemical bond- An attraction between two atoms by sharing outer-shell (or valence) electrons or from the presence of opposite charges on the atoms. Bonded atoms form complete outer shell. Here's an example of some elements and their chemical bonds forming molecules.

b. Covalent bond - stable chemical bond; 2 atoms share one or more pairs of valence electrons

c. Single bond one pair of shared electrons between atoms [|Single bond picture]

d. Double bond ~ A molecule is formed by the sharing of two pairs of valence electrons, known as double covalent bond

e. Valence - The bonding capacity of an atom's outermost shell.

f. Electronegativity- The attraction of a particular kind of atom for the electrons of a covalent bond (The more electronegative an atom, the more strongly it pulls shared electrons toward itself)



g. Nonpolar covalent bond

h. Polar covalent bond- A bond where one atom is bonded to a more electronegative atom and where the electrons of the bond are not shared equally (vary in their polarity which depends on the relative electronegativity of the 2 atoms)



10. What is the difference between a structural and molecular formula? A structural formula shows how the atoms are bonded while the molecular formula is just the abbreviated version Structural Molecular H-H H2



11. How do ionic bonds compare with covalent bonds? Covalent bonds are stronger than ionic bonds. Ionic bonds occur between oppositely charged metal and non-metal atoms. Covalent bonds occur between any atom.

12. Compare and contrast hydrogen bonds and van der Waals interactions. Hydrogen bonds are stronger than van der Waals interactions, but van der Waals interactions can occur between any atom. Both can occur along regions of a large molecule.

13. Based on the reading, what is an example, in a living system, of how molecular shape is critical?

14. Define a dynamic chemical equilibrium in terms of quantities of reactants and products. This is a critical concept! it occurs when two things are reacting to each other but the reactants have been stabilized at a particular ratio so that there is nothing produced as an effect to the reaction, but it does not mean the reactants are equal in terms of their quantity, just there reaction rate.