Creepy Covalent Bonds (please read the blog. I put a lot of work into it.)

HAPPY HALLOWEEN, EVERYONE... which calls for a special blog. hehehe

{in class: we went over the quiz and took notes. ON Tues.- Outline due and Ch. 5 test. ON Wed.- Ch. 6 quiz. START MEMORIZING THE TABLES 1,2,and 5 ON PGS. 221, 226, AND 230. Dr. B said, "if you want your grades to improve, start now!" Quizes will be taken by tables}

Formation of a Covalent Bond

• Most atoms (and zombies) have a lower Potential Energy when they are bonded with other atoms (or zombies) than when the atom/zombie is alone.
• The chart in our book on pg. 179 shows the P.E. changes during formation of H-H bond

(SHE ALWAYS ASKS QUESTIONS ABOUT THIS CHART!!!)

• Suppose you have two atoms: the electron of one atom ATTRACTS the proton of the other atom (like kids and candy)
• in these same atoms, the electrons in the different atoms REPEL each other (same with the protons) (like candy and evil dentists)

--> These forces cancel out to form a covalent bond where the P.E. is lowest (they are chained together for eternity!!!!!! or until something breaks them up...)

Characteristics of a Covalent Bond

(VOCAB ALERT!)

• bond length- the distance between two bonded atoms at the minimum P.E.

--> The average distance between two bonded atoms

• Atoms release energy forming covalent bonds (like a mummy released from the grave!)
• The same amount of energy must be added to separate the atoms (stuff that mummy back in the grave! haha Take that mummies!)

(VOCAB ALERT!)

• bond energy- the energy required to break a chemical bond and form isolated atoms

• Shared electrons of two atoms in a covalent bond form overlapping orbitals

--> atoms are jealous of noble gases, so they want to make their outer shells like a noble gas's (then they can overthrow the noble gases and rule the periodic table muahaha!)

ex.- two bonded H atoms (with the overlapping orbitals) can each have He's electron configuration

The Octet Rule

• the reason noble gases are unreactive is because their electron configuration is esp. stable

--> stability comes from full s and p orbitals

• Covalent bonding allows other atoms to reach this stability

(IMPORTANTE!!!)

• OCTET RULE- Chemical compounds tend to form sa that each atom, by gaining, losing, or sharing electrons, has an octet in its highest energy level

[THIS RULE APPLIES ONLY TO THE MAIN GROUP ELEMENTS IN THE 2ND PERIOD AND BELOW]

(ALSO IMPORTANTE!!!)

• There are exceptions to the octet rule!- any atoms that can't fit 8 electrons or can fit more than 8 electrons in its outermost energy shell
• the exceptions are- ARGGGGGGGGGGGGHHHHHHHHHHHHHHHHH! (the writer of this blog was dragged away by disgruntled zombies, an evil dentist, mummies, and jealous elements)

(we will cover what the exceptions are on Monday)

Chemical Bonding

Chapter VI: Chemical Bonding
10/29/09

NOTES:
Ionic bonding- chemical bonding that results from the electrical attraction between cations and ations

Covalent bonding- bonds that result from sharing of electron pairs between two atoms

• Nonpolar Covalent Bond- two atoms of same size bond
• Polar Covalent Bond- an atom bonds with an atom of a different size

Percentage Ionic Character-

• To find, subtract the electronegativity of two elements, then find the difference on the percentage ionic character.
• If 0-.3, then it's nonpolar covalent
• If .4-1.7, then it's polar covalent
• if 1.8-3.3, then it's ionic

Molecular Compounds

• a molecule is a neutral group of atoms that are held togethor by covalent bonds
• a chemical compound whose simplest units are molecules is a molecular compound
• the composition of compound is given by its chemical formula
• a chemical formula indicates the relative numbers of atoms of each kind in a chemical compound by using atomic symbols and numerical subscripts.
• a molecular formula shows the types and numbers of atoms combined in a single molecule of a molecular compound

Extra notes: Chapter 5 Test will be on Tuesday, November 3rd; The Chapter 5 outline will be due on the day of the test, Tuesday. Have a good afternoon.

10/28/09

The electrons in te both the cations and anions are in higher energy levels as one reads down a group.

There is a gradual increase of ionic radii down a group

Valence Elctrons

Chemical compunds for because electrons are lost, gained, orshared between atoms

The electrons that interacts in this manner are those in the highest energy level

The electrons available to be lost, gained, or shared in the formation of chemical compundsare referred to as valence elctrons

Valence electrons are often located in the incompletely filled main-enrgy levels

Example: The electron lost from the 3s sublevel of Na to form Na+ is a valence electon

Electronegativity

Valence electrons hold atoms togehter in chemical compounds

In many cmpounds, the negative charge of the valence eectron is concentrted closer to one atom than to another

Electronegativit is a measure of the ability of an atom in a chemical compound to attract electrons from another atom in the compound

Electronegatvities tend to increase across periods and decrease or remain about the same down a group

Need to Know on the Periodic Table

Groups 1 and 2

Inner T.M

Main Group(s&p)

Halogens(17)

Noble gases(18)

Metals(+ ions)

Nonmetals(-ions)

Metaloids

Atomic radius increase from bottom up and right to left

Ionization energy incrreases from bottom to top and left to right

Electron affinity increases bottom to top and left to right

Electronegativity increases bottom to top and left to right

ions!

(+) Cations smaller than original atom

(-) Anions larger than originl atoms

Chapter 3

Electron Affinity

• The energy change that occurs when an electron is acquired by a neutral atom is called that atom's electron affinity
• Electron affinity generally increases across periods
• Increasing nuclear charge along the same sublevel attracts electrons more strongly
• Electron affinity generally increases down groups
• The larger an atom's electron cloud is, the farther away its outer electron are from its nucleus

Ionic Radii

• A positive ion is known as a cation
• The formation of a cation by the loss of one or more electrons always leads to a decrease in atomic radius
• The electron cloud becomes smaller
• The remaining electrons are drawn closer to the nucleus by its unbalanced positive charge
• A negative ion is known as an anion
• The formation of an anion by the addition of one or more electrons always leads to an increase in ionic radius
• Cationic and anionic radii decrease across a period

10-26-09

Regarding the dart lab: It's due Thursday. Use a line graph for the graphs. Clarity is important; neatness isn't. If you had hits outside of the circle, add a row for >10cm, calculate the area of the sheet of paper (remember to convert inches to centimeters), and add your data. Hits are infinitely significant for calculations. The figure on the sheet is not the one from you book. Use Fig. 11 on page 107.

Atomic Radii

• The boundaries of an atom are fuzzy, and an atom's radius can vary under different conditions.
• To compare different atomic radii, they must be measured under specific conditions.
• Atomic radius may be defined as one-half the distance between the nuclei of identical atoms that are bonded together.
• Atoms tend to be smaller the farther to the right they are found across a period.
• The trend to smaller atoms across a period is caused by the increasing positive charge of the nucleus, which attracts electrons toward the nucleus.
• Atoms tend to be larger the farther down in a group they are found.
• The trend to larger atoms down a group is caused by the increasing size of the electron cloud around an atom as the number of electron sublevels increases.

Sample Problem E

Of the elements Mg, Cl, Na, and P, which has the largest atomic radius? Highlight for answer. Na. All of these elements are in the same period, and Na is right-most.

Ionization Energy

• An ion is an atom of group of bonded atoms that has a positive or negative charge.
• Na, for example, easily loses an electron to form Na+.
• Any process that results in the formation of an ion is referred to as ionization.
• The energy required to remove one electron from a neutral atom of an element is the ionization energy, IE (or first ionization energy, IE1).
• In general, ionization energies of the main-group elements increase across each period.
• This increase is caused by increasing nuclear charge.
• A higher level charge more strongly attracts electrons in the same energy level.
• Among the main-group elements, ionization energies generally decrease down the group.
• Electrons removed from atoms of each succeeding element in a group are in higher energy levels, farther from the nucleus.
• The electrons are removed more easily.

P.S. Since I'm such a nice guy, I'll give somebody a chance to volunteer to do the blog tomorrow. If nobody does, I'm going to pick somebody using a random number generator, so no whining if luck doesn't favor you.

10/22/09

We have a lab tommorow
-Each person in the group drops it 50 times at shoulder length with arm extended
-Record where it sticks in the target after each drop
-If it doesn't go through the paper, mark an x where it hit
-You decide whether it is in or out if it lands on a line
-Don't poke people with the darts (Ben).

Notes
-The 3d sublevel is higher in energy than the 4s sublevel, so they are filled in the order
4s3d
-D Block metals are typically have metallic properties and are often referred to as
transition elements
-P Block elements consist of all the elements of Groups 13-18 except helium.
-The p Block elements together with the s Block elements are called the main-group
elements
-Properties of elements of the p Block vary greatly.
-At it's right hand-end, the p Block includes all of the nonmetals except hydrogen
and helium
-All 6 of the metalloids are also in the p Block
-At the left-hand side and bottom of the block, there are 8 p Block metals.
-The elements of group 17 are known as the halogens
-flourine, chlorine, bromine, iodine, and astatine
-The halogens are the most reactive nonmetals
-They react vigourously with most metals to form examples of the type of
compound known as salts
-The metalloids, or semiconducting elements, are located between nonmetals and metals in
the p Block
-The metals of the p Block are generally harder and denser than the s Block alkaline earth
metals, but softer and less dense than the d Block metals
-In the periodic table, the f Block elements are wedged between Groups 3 and 4 in the
sixth and seventh periods
-Their position reflects the fact that they involve the filling of the 4f sublevel.
-The first row of the f Block, the lanthanides, are shiny metals similar in reactivity to the
Group 2 alkaline metals
-The second row of the f Block, the actinides, are between actinium and rutherfordium.
These actinides are all radioactive.

Ch.5 Sec 1 and 2

Ch. 5 Sec 1

1. Periodic Table

• An arrangements of the elements in order of their atomic number so that elements w/ similar properties fall in same column or group
• Elements are arranged vertically in the P.T.(periodic table) in groups that share similar chemical properties

Ch. 5 sec. 2

Periods

• Elemts organized horizontally in rows
• Length of each period is determined by # of electrons that can occupy the sublevels being filled in that period
• The P.T. is divided in 4 blocks, s p d & f; the name of each block is chosen by the electron sublevel being filled in that block (disregarding Hydrogen and Helium b/c they are too small)

Alkali metals

• Elements of group 1 on P.T.
• Lithium, Sodium, potassium, rubidium, cesium, and francium are the Alkali metals
• In alkali metals's pure state, they all have a silvery appearance and are soft enough to cut w/ a knife

Alkaline-earth metals

• Elements in group 2 of P.T.
• Beryllium, magnesium, calcium, strontium, barium, and radium (all Alkaline-earth metals)
• Less reactive than alkali metals, but are still too reactive to be found in nature in pure form

• Hydrogen has an electron configuration of 1s1 but despite the ns2 configuration, it doesn't share the same properties as elements of group 1
• Hydrogen is an unique elments

• Like the Group 2 elements, helium has an ns2 group configurtaion, yet it is part of group 18
• B/c its highest occupied energy level is filled by 2 electrons, helium posses special chemical stability

P.S. remember to do Pre-Lab for tomorrow