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1. Contrast the term element with compound. Smiley-02-june.gif

An element is a substance that cannot be broken down into other substances by chemical reactions. A compound is a substance consisting of two or more different elements combined in a fixed ratio. An example of an element is K (Potassium). An example of a compound is NaCl (Sodium Chloride). 

-Mr V

2. Upload a diagram/ animated model/ or video of an atom and explain the components. Include and electron cloud model and a bohr model. Smiley-02-june.gifexternal image moz-screenshot.png
In this diagram of a helium atom,
electrons are shown as a cloud representing all the places the two electrons may
have been at any time.In the diagram of a helium atom on the right, the two electrons are shown as
orbiting dots on a ring around the nucleus.

Proton =
Electron cloud (Schrodinger) model
Electron cloud (Schrodinger) model
Bohr model
Bohr model

Electron = BLUE
Neutron =WHITE or ORANGE
Nucleus =

Proton- a subatomic particle with a charge of +1
Nucleus- contains the protons and neutrons
Electron-a subatomic particle with a charge of -1
Neutron- a subatomic particle with a charge of 0.

3. Contrast the terms atomic mass and atomic number. Smiley-02-june.gif

Atomic mass or atomic weight is the total mass of an atom, which is the mass in grams of one mole of the atom. It is calculated using the relataive abundance of isotopes in a natural occuring element.
Atomic number is the number of protons in the nucleus of an atom. It is the same as the charge number of the nucleus. The atomic number is equal to the number of electrons.



4. What is the difference between the terms atomic mass and atomic weight? Smiley-02-june.gif
Atomic mass is the total mass of the atom at rest which describes (one) isotope of the particular element. Atomic weight however is the abundance (more than one isotope) weighted average mass of an element. In more simple terms, the atomic mass is the total mass of an atom while atomic weight is the weighted average mass of an atom.



5. What is an isotope and what is “special” about radioactive isotopes? Smiley-02-june.gif

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 give off particles and energy. They are useful as tracers to follow atoms through metabolism.


- Kelly

6. Explain how radioactive tracers are used in science? Smiley-02-june.gif
Radioactive tracers have several uses in science. Among those uses they can help to monitor biological processes, by allowing cells to make copies of their DNA. They can also follow both metabolic and chemical processes. As medical use: Used as a diagnostic tool for imaging. Radioactive tracers can also be used by injecting doses of the substance in order to cure a disorder.

external image MRI.jpg

-Dahlia M.

7. Explain how the movement of electrons relates to the concept of potential energy – use the diagram below to help answer the question. Smiley-02-june.gif
external image moz-screenshot-1.png
a) b)

external image moz-screenshot.png-Alina D.

a) The ball can come to a stop every step but not in between, which is an excellent example of how electrons move between energy levels.
b) An electron can move fromone energy level to the next only if the energy it the energy it gains or losses is exactly equal to the difference in energy between the two levels.

- Alina D.

8. What determines interactions between atoms? Why are valence electrons important? Smiley-02-june.gif

The complete and incomplete valence shell determines whether atoms interact with each other. This has to do the electro-negativity of the atom. The more valence electrons, the more want for the atom to get more electrons.
The valence is the outer most . Valence electrons are important because it determines the chemical behavior.

valence2 -Mike G.

9. Define the following terms and give examples (pictures):Smiley-02-june.gif

Chemical bond – an attraction between atoms that results in them staying close together (covalent/ionic)
Covalent bond – the sharing of a pair of electrons by 2 atoms
Single bond – a single pair of shared electrons
Double bond – atoms sharing 2 pairs of valence electrons
Valence – bonding capacity of an atom; usually equals the number of unpaired electrons in the atoms outermost shell
Electronegativity- attraction of a particular kind of atom for the electrons of a covalent bond
Polar covalent bond – where one atom is bonded to a more electronegative atom the electrons are not shared equally

Ryan H.

10. What is the difference between a structural and molecular formula? Smiley-02-june.gif
structural - a line represents a single bond, represents both atoms by bonding (ex. H-H)
molecular - indicates simply what the molecule consists of (ex. H

Ryan H.

11. How do ionic bonds compare with covalent bonds? Smiley-02-june.gif
In ionic bonds, one atom gives another atom electrons to satisfy both of their valence shells and create two octets. In covalent bonds atoms share electrons, because both atoms require the same electrons to create an octet.-Sam B.

Ionic Bond Covalent Bond
external image ionic_bonding.gifexternal image covalent_bonding.gif

12. Compare and contrast hydrogen bonds and van der Waals interactions. Smiley-02-june.gif
Hydrogen bonds occur when hydrogen covalently bonds with another electronegative atom. Hydrogen bonds and van der Waals interactions are both very weak. However, Van der Waals forces can occur between any two atoms if close enough while hydrogen bonds can only occur between hydrogen, and either oxygen or nitrogen.

-Sam B.

Hydrogen Bonding Van der Waals Forces
external image 9_7.jpg

13. Based on the reading, what is an example, in a living system, of how molecular shape is critical?
I think you are trying to describe the relationship between signal molecules and receptor proteins embedded in the membrane of nerve cells. Can you clarify your example. You also could describe how enzymes work.
Molecular shape is very critical in a living system. It is almost like a key and a lock. The key has to be the right shape for it to fit into the lock. It determines how most biological molecules recognize and respond to one another. For example, when signal molecules release its signal, it releases a unique shape that specifically fits together with the shape of the receptor molecules on the surface of the receiving cell.

14. Define a dynamic chemical equilibrium in terms of quantities of reactants and products. This is a critical concept!Smiley-02-june.gifDynamic chemical equilibrium is the point at which reactions offset each other exactly, and a product is produced.
Example of how a product is produced: (Hydrogen and Oxygen are the reactants and water is the product.)