Ch 2 Collaboration

Collaboration Teams - Members share responsibility for posting refined answers to the guided readings - succinct, relevant, clear, and with pictures or a video to compliment.
When contributing to the reading guide, follow these steps:
1) First complete the reading guide on your own from the chemistry unit page.

2) Write your response to a question in word and then copy it. Be sure to upload pictures and/or video for each question.
3) Click on the edit button and then go to the appropriate question and paste your answer below it. Sign your contribution with your first name and last initial and TEAM COLOR
Scroll to the very bottom and in the Optional comment box, place a summary of what you did and sign it (e.g. "I answered chp 26 question 3" - Tom S.) Th en click Save.








1. Contrast the term element with compound. Smiley-02-june.gif
An element is a substance that cannot be broken down to other substances by chemical reactions while a compound is a substance consisting of two or more different elements combined in a fixed ratio.

2. Upload a diagram/ animated model/ or video of an atom and explain the components. Include and electron cloud model and a bohr model.
Please Explain Components

atom.jpg Electron cloud model

Nucleus- center of the atom
Cloud of negative charge- the negative charge of electrons flying around the nucleus close to the speed of light
Electrons- electrically charged, negative

Protons- electrically charged, posititve
Neutrons- no charge

atom_model_04.gifBohr Model

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

Each element has a different number of protons that is unique to that element, called the atomic number, telling us how many protons are in its nucleus. The number of protons in an element is always equal to the number of electrons because they balance out, so the atomic number also tells how many electrons are in a particular element. The mass number of an element is the sum of protons plus neutrons in the nucleus of an atom. The number of neutrons can be determined by subtracting the atomic number from the mass number. Since neutrons and protons both have a mass close to 1 dalton, the mass number is approximately the total mass of an atom, which is its atomic mass.

4. What is the difference between the terms atomic mass and atomic weight? Smiley-02-june.gif

Mass is defined as the amount of matter in an object. In terms of atoms, the mass is describes as the amount of protons and neutrons in an atom in daltons. The number of protons in an atom equals the amount of neutrons. Atomic weight describes the number of protons plus the number of neutrons in an atom. The atomic weight is the average atomic mass of all of the atoms in an element.

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

external image tim_isoth.gif
An isotope is an atom differing in the number of neutrons it has so it is still the same element with the same number of protons and electrons, but with a different atomic mass. In a radioactive isotope, the nucleus decays spontaneously and destroys protons, transforming it into an atom of another element.

- Kim, Jared and Jordan

6. Explain how radioactive tracers are used in science? Smiley-02-june.gif

Radioactive tracers can be used to follow atoms through metabolism. Radioactive isotopes can also be used to facilitate a PET scanner in identifying cancerous growths.

Where the arrow is pointing shows a cancerous growth which is illuminated because of an injection of radioactive isotopes
Where the arrow is pointing shows a cancerous growth which is illuminated because of an injection of radioactive isotopes

- Kim, Jared and Jordan

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

Electrons can’t float in between energy levels just as the ball can’t float in between stairs. The arrows pointing away from the nucleus show the atom absorbing energy. The arrows pointing inward show the atom losing energy. Depending on which energy level an electron is on determines the amount of potential energy the atom has. - Alyssa C.

8. What determines interactions between atoms? Why are valence electrons important? Smiley-02-june.gif
The number of the valence electrons in its outermost shell determines how atoms interact. They are important because they determine the reactivity of the element. If two atoms have their valence shells filled then they will not interact with each other, but if two atoms valence shells are not filled then they can interact with each other and share valence electrons.


Zack and Mario

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

Chemical bond--
An attraction between two atoms, resulting from a sharing of outer-shell electrons or the presence of opposite charges on the atoms. The bonded atoms g
ain complete outer electron shells (the valence shell).
An example would be any bond between any atoms like a water molecule or the bond between Na and Cl (table salt).

Covalent bond—
A type of strong chemical bond in which two atoms share one or more pairs of valence electrons (Ve-).
An example of a covalent bond is H2O.

Single bond—
When there is a single pair of shared electrons between the two atoms
Example is of two hydrogen atoms bonding together. H—H.

Double bond—
When there are two pairs of valence electrons being shared between the two separate.
Example would be the oxygen gas atoms. The two oxygen atoms bond together O=O.

The bonding capacity of an atom, generally equal to the number of unpaired electrons in the atoms outermost shell (full valence eight electrons).
When two hydrogens attach to the oxygen atom the amount of electrons in the outermost shell (valaince shell) now has a full 8. This is why water is H2O not H3O (if the valance was 9).

The attraction of an atom for the electrons of a covalent bond. It is how attractive one atom is to another atom.

Example: Nitrogen is a lot more electronegative than Magnesium.

Nonpolar covalent bond—
A type of covalent bond in which electrons are shared equally between two atoms of a similar electronegativity.
Example: The bonds between two hydrogen bonds they are linear.

Polar covalent bond—
A covalent bond between atoms that differ in electronegitivity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive
Example: The bonds in a water atom, between the hydrogen and oxygen atoms. They are more polar towards the oxygen atom.

Brian, Sean, and Jackie --> yellow team

10. What is the difference between a structural and molecular formula? Smiley-02-june.gif
The structural formula is a type of molecular notation in which the constituent atoms are joined by lines representing the lines. And the molecular formula is a type of molecular notation indicating only the quantity of the constituent atoms.

Ex. Structural: H—H O=O
Molecular: H2 or Hydrogen gas O2 or Oxygen gas

11. How do ionic bonds compare with covalent bonds? Smiley-02-june.gif
A covalent bond is the sharing of a pair of valence electrons by two atoms, such as two hydrogen atoms. Each has one electron on their valence shell and both need another electron to fill the shell. When their orbital’s overlap, they are able to share each other electrons and form an H2 molecule. Ionic bonds however, do not involve sharing electrons. An ionic bond includes a cation and an anion, which are attracted to each other because of their opposite charges. When this bond is formed, one atom takes a valence electron from another atom, while the other atom loses the atom, leaving it with a full valence shell at a lower level, resulting in two separate ions.

Keely B

12. Compare and contrast hydrogen bonds and van der Waals interactions.
van der waals are a little different but not to worry for Bio AP

A hydrogen bond is a weak attraction between one electronegative atom and a hydrogen atom that is covalently linked to another electronegative atom. Van der Waals interactions occur when transiently positive and negative regions of molecules attract each other. Both are relatively weak reactions, but have an important cumulative effect of reinforcing the size and shape of a particular molecule.
external image water.gifexternal image VanderWaals1.gifVan Der Waals

Based on the reading, what is an example, in a living system, of how molecular shape is critical? Smiley-02-june.gif
Shape is critical as the basis for the recognition of one biological molecule by another. For example, pain control is a mechanism where dopamine binds to receptors on the surface of brain cells, relieving pain and producing euphoria. Molecules with shapes similar to dopamine have the same effects they do. Morphine, heroin, and other opiates mimic dopamine by binding to end1.jpgorphin receptors in the brain.
-Amanda P.

14. Define a dynamic chemical equilibrium in terms of quantities of reactants and products. This is a critical concept!

Chemical equilibrium is a state in which chemical activities or concentrations of the reactants and products have no net change over time.