Chemical Structures

D 10. Describe the general structure of the atom, and explain how the properties of the first 20 elements in the Periodic Table are related to their atomic structures.

An atom consists of a nucleus, which contains charged particles called protons and neutrally charged particles called neutrons. Negatively charged particles called electrons surround the nucleus in different shells. The capacity for each shell is described in the table below. Electrons of higher energy are located in the outside shells....



(1)This is an example of a Zinc atom. As you can see there are 30 electrons, with the correct number of electrons in each shell.



Shell
Maximum # of electrons
1
2
2
8
3
8
4
18


In order for an atom to have stability, all occupied shells must be exactly full. The noble gases are the only elements that fit this criteria. This makes noble gases extremely nonreactive.

For an atom to have a neutral charge, the number of protons and electrons are the same. Sometimes, however, an atom can lose or gain electrons. An ion is an atom that has lost or gained electrons, giving it a positive or negative charge. A cation is positively charged ion and an anion is a negatively charged atom.


Elements with the smallest charge (+ or -) are most reactive. The most reactive elements are on
either the left
side of the periodic table.
On the periodic table, elements are listed from left to right in order of increasing numbers of protons (also electrons for neutral atoms). The atomic mass of each element is the sum of protons and neutrons (each 1 gram) and electrons (remaining mass). The number is the average of all the isotopes of that element.


Bohr model of the atom, created 1913
http://www.youtube.com/watch?v=hpKhjKrBn9s (2)




D 11. Describe how atoms combine to form new substances by transferring electrons (ionic bonding) or sharing electrons (covalent bonding).

Ionic bonding is a type of chemical bond that can form between metals and non-metals. The metal loses electrons, forming a cation, while the non-metal gains electrons, forming anions. Because these ions have opposite charges, they attract each other, forming what is known as an ionic compound. Covalent bonding takes place when atoms share electrons with each other. As a result, attracting-to repulsion stability forms between atoms.

Ionic and covalent bonds
http://www.youtube.com/watch?v=ERy18NwemVc
(3)An example of covalent and ionic bonds.
(3)An example of covalent and ionic bonds.

(3)An example of covalent and ionic bonds.



D 12. Explain the chemical composition of acids and bases, and explain the change of pH in neutralization reactions.

Acids: composition includes one or more hydrogen ion (H+) and has a pH of less than 7

Bases: composition includes one or more hydroxide anion (OH—) and has a pH of greater than 7

Acid-Base Neutralization: an acid and a base react as much as possible to try to get to a neutral pH, or 7 on the pH scale. This process forms neutral products, a salt and H2O.

Ex. 2Na + 2H2O à 2NaOH + H2

(4)This is the PH scale which tests a substance for acidity. The closer the result is to 0, the more acidic it is. The closer the number is to 14, the more basic it is. 7 is considered neutral.
(4)This is the PH scale which tests a substance for acidity. The closer the result is to 0, the more acidic it is. The closer the number is to 14, the more basic it is. 7 is considered neutral.

(4)This is the PH scale which tests a substance for acidity. The closer the result is to 0, the more acidic it is. The closer the number is to 14, the more basic it is. 7 is considered neutral.

This is the PH scale which tests a substance for acidity. The closer the result is to 0, the more acidic it is. The closer the number is to 14, the more basic it is. 7 is considered neutral.





D 13. Explain how the structure of the carbon atom affects the type of bonds it forms in organic and inorganic molecules.

Inorganic:

Carbon can bond to several inorganic compounds including: oxides (CO2); carbonates and bicarbonates (CaCO3); carbonic acid (H2CO3); carbonyls (Cr(CO)6); CN group compounds (HCN); or carbides (TaC). Carbon can also inorganically form lead or diamond.

Organic:

All organic compounds contain carbon. These include: hydrocarbons, aliphatic compounds, aromatics, polymers, and biomolecules.
(5)Hydrocarbon atom (organic)
(5)Hydrocarbon atom (organic)

(5)Hydrocarbon atom (organic)

(5)Carbon atom
(5)Carbon atom

(5)Carbon atom




D 14. Describe combustion reactions of hydrocarbons and their resulting by-products.

A hydrocarbon is an organic compound that consists entirely of carbon and hydrogen. When a hydrocarbon is completely combusted in pure oxygen, it only emits CO2 and H2O as the resulting products. However, it is impossible to get a complete combustion of a hydrocarbon because the atmosphere contains a mixture of different elements, such as nitrogen, sulfur, and iron. When present, these elements can, too, combust in the air, forming various oxides such as carbon monoxide and sulfur dioxide.
examples of combusion reactions
examples of combusion reactions

examples of combusion reactions

Examples of Combustioin Reactions


D 15. Explain the general formation and structure of carbon-based polymers, including synthetic polymers, such as
polyethylene, and biopolymers, such as carbohydrate.
Polymers are linked monomers.
HyrdroCarbons are carbon based monomers. They are composed entirely of hydrogen and carbon. The hydrocarbon ethene forms the polymer polyethylene. The structure of polyethylene is a long chain of ethene. The bonding of monomers is called polymerization. . Some of the categories are:
UHMWPE(Ultra High Molecular Weight Polyethylene) is polyethylene with a molecular weight numbering in the millions. It is usually between 3.1 and 5.67 million.
HDPE(High Density Polyethylene) is defined by a density of greater or equal to 0.941 g/cm3
PEX(Cross Linked Polyethylene) is a medium- to high-density polyethylene containing cross-link bonds.
MDPE(Medium Density Polyethylene) is defined by a density range of 0.926–0.940 g/cm3..
LLDPE(Linear low density Polyethylene) is defined by a density range of 0.915–0.925 g/cm3. LLDPE is a substantially linear polymer, with significant numbers of short branches.
LDPE(Low Density polyethylene is defined by a density range of 0.910–0.940 g/cm3. LDPE has a high degree of short and long chain branching.
VLDPE(Very Low Density Polyethylene) is defined by a density range of 0.880–0.915 g/cm3. VLDPE is a substantially linear polymer, with high levels of short chain branches.





D 16. Explain how simple chemical monomers can be combined to create linear, branched and/or cross- linked
polymers.
A monomer is a simple chemical molecule that can be bonded with other monomers to form polymers. The simplest form of a polymer molecule is the linear polymer. The structure of the linear polymer is simply a straight chain of monomers. Branched polymers are composed of a main change

Polymer_Branch.png
Polymer_Branch.png

Branched Polymer

Branched Polymer
and the side chains that branch off of the main chain. The cross link polymer is a polymer from which four chains originate. When a polymer has an abundant amount of cross linking it is called a polymer network. .




D 17. Explain how the chemical structure of polymers affects their physical properties.

A polymer’s physical properties is greatly affected by what it is composed of. .
Chain length - An increase in chain length can result in a decrease in chain mobility. It also results in increased “toughness” and strength.
Branching - Polymer chains with shorter and more random branches usually reduce strength due to lack of organization. Polymer chains with long chain branches can increase strength, toughness, and the glass transition temperature.
Chemical Cross-Linking - Cross-linking is the formation of chemical bonds between chains. This process has many applications, however, most commonly, it is used as a form of vulcanization. In vulcanization, sulfur is cross-linked to other polymers. Car tires are cross-linked so that little to no air can escape. Eraser rubber is not cross-linked, as flaking of the rubber is necessary to prevent damage to the paper being erased.


external image figure2.gif
external image figure2.gif
(a polymer)


D 18. Explain the short- and long-term impacts of landfills and incineration of waste materials on the quality of the environment.

(trash dumps)​ have different​ hits/effects​ on the surrounding (surrounding conditions)​. These include air pollution, contamination of surface waters, changes in (wide view of a nature scene/wide area of beautiful land)​ (went with​ by “visual discomfort”), and changes in soil life-creating ability​. In (lots of different living things all existing together)​ terms, (trash dumps)​ can result in the elimination of 30 to 300 species (microbiological population of the soil not included). Most of the effects are long-term. The most important short-term hit/effect​ are bad smells (which cause irritation to the surrounding (community of people/all good people in the world)​).
Another major problem that recyclable materials are mixed with non-recyclable materials. Consequently, these two very different materials blend together and become chemically contaminated.

external image fig3_3.gif
external image fig3_3.gif

external image fig3_3.gif