December 13

Thursday, December 13, 2012

Due Tomorrow: Periodicity Worksheet. The Alternate Universe Chemistry worksheet is not due until Monday. THE TEST HAS BEEN MOVED TO TUESDAY, 12/18.

Today in class, we spent the majority of the class going over the class notes. We learned about atomic radius, ionization energy, and a little bit of electronegativity.

     Atomic radius, simply put, is the radius, or size, of an atom. We learned that similarly to the Periodic Table of the Aliens, as you move up and down columns and left to right through the rows of the periodic table, the elements have similarities as well as one or two changing variables. For atomic radius, as you move left to right on the periodic table, the radius decreases. This is because as you move left to right, the elements have more protons, which bond with the electrons, drawing the atom tighter together, making the radius smaller. We also noticed the trend that, as you move down the families, the radii increases because there are more electrons as you move down, but not as many protons, which means that the size (radius) will increase. This trend is the opposite for both ionization energy and electronegativity.

     Ionization energy is the amount of energy required to remove one valance electron (an electron on the outer shell of the atom) from the atom. As I mentioned above, the trends of ionization energy are opposite to the trends of the atomic radius. As you move from left to right on a period, the energy needed to remove one electron increases. This is because as you move across the period, as mentioned above, the elements gain protons, drawing the atoms tighter together. Because the elements become more compact, the energy needed to pull one electron out increases. Similarly, as mentioned above, as you move down a family, the amount of electrons increase, but the amount of protons does not, so the atoms are less compact. This makes the amount of energy needed to pull out one electron less.

     The trends of electronegativity are exactly the same as ionization energy, for similar reasons. Electronegativity is the ability of an atom to attract electrons. As you move left to right across a period, the outer shell of atoms becomes more full. This means that as you move left to right, atoms need less and less electrons. The pull that they have to complete their electron shells becomes greater.

Go on Moodle if you need tonight's homework.

The next scribe will be.... Jack M.

Ionic and Covalent Bonds

Ionic and Covalent Bonds


Homework for Monday: Naming Practice worksheet
                                       Quiz Monday- Covalent Naming

On Thursday and Friday, we began to study two types of bonds between atoms, ionic and covalent bonds.


Ionic bonds
      On Thursday we began learning about ionic bonds. An ionic bond is a bond formed between one positive and one negative atom. We began with a worksheet that helped us better understand what an ionic bond was. For example, we had to list any similarities that we noticed between several examples. These similarities included that the first element in an ionic bond was a metal, and that the second element was a non-metal that ended with the suffix -ide. Below is an example of how an ionic bond is formed.
Ionic bond:

On Friday, we started class with a short quiz on ionic bonds. After the quiz, we started a worksheet, similar to the one about ionic bonds, that introduced us to covalent bonds.

Covalent bonds

     On Friday after the quiz, we began to learn about covalent bonds. As mentioned above, we started a worksheet that introduced us to covalent bonds. A covalent bond is a bond formed between two atoms that share electrons. We identified patterns that we noticed between examples given on the worksheet. Some similarities were that the second element ended with -ide, both elements used Greek prefixes, and the first element is a non-metal. 

Covalent bond:

We also began learning how to name and identify the two types of bonds. Some examples for naming ionic bonds are:

Copper (I) Chloride ---> Cu2Cl

and Iron (III) oxide   ---> Fe2O3

Covalent bonds use Greek prefixes for naming compounds. Some examples for naming covalent bonds are:

NO2 ---> Nitrogen dioxide

CO   ---> Carbon monoxide    If you noticed, in this example a prefix for carbon was not added, because as a rule prefixes              .                                                   are only added to the first atom in a covalent bond if there is more than one. For example:

P2O5 is diphosphorus pentoxide

The quiz monday will cover covalent bonds and covalent naming, as explained above.

The next scribe will be Johnny O.