Period+2+chem+ch2

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

1. Contrast the term element with compound.

An element is a substance that is in its simplest form. beal. . . and can't be broken down into anything else. A compound is a substance consisting of 2 or more elements.

​ 2. Label the diagram below and define the terms that you label. ​ ​beal. . what's in the nuclues?

3. Contrast the terms atomic mass and atomic number. ​ ​beal. . atomic number also tells the number of electrons!
 * **Atomic mass is the total mass of the atom**
 * **measured in daltons**
 * **atomic number is the number written to the left of the element as a subscript**
 * **tells the number of protons**

4. What is the difference between the terms atomic mass and atomic weight?

beal. . good.
 * **//atomic mass is the mass of an atom at rest//**
 * **//measured in daltons//**
 * **//atomic weight is the abundance-weighted average mass of an element//**
 * **//average weight of isotopes that exist is determined by seeing how abundant each isotope is in nature //**

5. What is an isotope and what is “special” about radioactive isotopes? an isotope is one of several atomic forms of an element, each containing a different number of neutrons and thus differing in atomic mass. Radioactive isotopes are special because when they decay and give off energy it changes its atom to make a different element.

beal. . good.

6. Explain how radioactive tracers are used in science? Tracers are used to follow a metabolic process or locate the substances



beal. . ummm. . . . see period 3.

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

A) A ball bouncing down a flight of stairs proviedes and analogy for energy levels because a ball can only rest on the individual steps, not in between. An electron cannnot stay fixed between potetial energy states. B) The electrons of an atom have potential energy because of their position in relation to the nucleus. The negatively charged electrons are attracted to the positively charged nucleus. The more distant the electrons are from the nucleus, the greater their potential energy.

beal. . good.

8. What determines interactions between atoms? Why are valence electrons important? The interactions between atoms is determined by the number of electrons in the valence shell, resulting in chemical behavior. Valence electrons are important because they determine if the atom will gain electrons from another atom or give away electrons to another atom. If the valence shell is filled, the atom will be nonreactive (inert). If the valence shell is incomplete, the atom will be reactive

beal. . good.

9. Define the following terms: a. Chemical bond- An attraction between two atoms, resulting from a sharing of outer-shell electrons or the presence of aopposite charges on the atoms. The bonded atoms gain complete outer electron shells. There are two types covalen and ionic bonds.

b. Covalent bond- A type of strong chemcial bond in which two atoms share one or more paris of valence electrons. There are many examples of covalent bonds but one of them is water:

c. Single bond- Also called Single covalent bonds, a pair of shared electrons.

d. Double bond- Also called double covalent bonds, when two atoms form a molecule by sharing two paris of valence electrons.

e. Valence- The bonding capacity of an atom, generally equal to the number of unparied electrons int he atom's outermost shell. For example the bonding capacity for oxygen is 2. f. Electronegativity- The attraction of an atom for the electrons of a covalent bond.

g. Nonpolar covalent bond- A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity. For example, a covalent bond of H2 and bouble bond of O2 are both nonpolar:

h. Polar covalent bond- A covalent bond between atoms that differ in elecronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative atom and the other atom slightly positive. The bonds between the oxygen and hydrogen atoms of a water molecule are polar. beal. . good.

10. What is the difference between a structural and molecular formula? A structural formula is a type of molecular notation in which the constituent atoms are joined by lines representing covalent bonds while a molecular formula is a type of molecular notation indicating only the quantity of the constituent atoms. The frist is a structural formual and the second is a molecular formula: beal. . molecular notation is like H2O. 

11. How do ionic bonds compare with covalent bonds? beal. . umm. . . both complete the outer e shell. ionic are made between a cation and an anion based on who is gaining or losing electrons. covalent is when the electrons are shared. what the heck is the below?
 * **Polarity:** || Low || High || hide ||
 * **Formation:** || A covalent bond is formed between two non-metals that have similar electronegativities. Neither atom is "strong" enough to attract electrons from the other. For stabilization, they share their electrons from outer molecular orbit with others || An ionic bond is formed between a metal and a non-metal. Non-metals(-ve ion) are "stronger" than the metal(+ve ion) and can get electrons very easily from the metal. These two opposite ions attract each other and form the ionic bond. || hide ||
 * **Examples:** || Methane (CH4), Hydro Chloric acid (HCl) || Sodium chloride (NaCl), Sulphuric Acid (H2SO4 ) || hide ||
 * **Melting point:** || Low || High || hide ||
 * **What is it?:** || Covalent bonding is a form of chemical bonding between two non metallic atoms which is characterized by the sharing of pairs of electrons between atoms and other covalent bonds. || Ionic bond, also known as electrovalent bond is a type of bond formed from the electrostatic attraction between oppositely charged ions in a chemical compound. These kinds of bonds occur mainly between a metallic and a non metallicatom. || hide ||
 * **Boiling point:** || Low || High || hide ||
 * **Occurs between:** || Two non metals || One metal and one non metal || hide ||
 * **State at room temperature:** || Liquid or gaseous || Solid || hide ||
 * **Shape:** || Definite <span class="IL_AD">shape || Has no definite shape ||

12. Compare and contrast hydrogen bonds and van der Waals interactions. They both provide examples of intermolecular bonding, and hydrogen bonds are part of the van der Waals interactions. Hydrogen bonds are the strongest intermolecular force. The bond between hydrogen and other gases. Van der Waals interactions are the weakest and occur between any molecule. In a chemical equilibrium the rate of the forward and backward reaction is the same. The concentration of products and reactions is constant.

beal. . umm. . .see period 3.

13. Based on the reading, what is an example, in a living system, of how molecular shape is critical? **Molecular shape is important because is determines how molecules respond to one another. Only molecules with complementary shapes are able to bind to each other by weak bonds. An example of this can be seen in the apin control mechanism in our bodies involving endorphins and their receptors. Natural signal molecules endorphins bind to specific molecules, receptors, on the surface of brain cells. This produces euphoria and relieves pain. Molecules with simliar shapes to endorphins, such as morphine, heroin, and other opiates, can also bind to these receptors and produce simliar effects.** beal. . . good, but what is a living system?

14. Define a dynamic chemical equilibrium in terms of quantities of reactants and products. This is a critical concept! a chemical equilibrium is where the reaction equal each other out exactly. The amount of products of products do not have to be equal but they must be met in a stabilizing ratio. The reactions should equal eachother out, the quantities should be in a ratio that suites the equation and the products left over should not be greater or lesser the original matter.

beal. . . good.