In the case of ammonia, the three 2p orbitals of the nitrogen atom are combined with the 2s orbital to form four sp3 hybrid orbitals. The non-bonded electron pair will occupy a hybrid orbital. Again we need a hybrid orbital for each atom and pair of non-b
Naming Molecular Compounds Most elements can be drawn by just using the symbols. However, the most stable form for many elements is a compound rather than the individual atom. The most common examples of these binary (2 atom) compounds are shown in the fo
When a hydrogen atom forms compounds with the nonmetals, the hydrogen atom is named first and the nonmetal is named as if it were a negative ion.
hydrogen fluoride.The (g) for (gas state) must be shown since HF in a solution of water is called hydrofluori
Never use the mono prefix for the first element and always use a prefix for the second element.
CO NO N2O PCl3 CCl4 carbon monoxide nitrogen monoxide dinitrogen monoxide.laughing gas phosphorus trichloride carbon tetrachloride
Deciding Which Nomenclature
Transfer of Thermal Energy A common unit of energy is the calorie. A calorie is defined as the amount of heat that is needed to raise the temperature of one gram of water one degree centigrade. Modern convention uses a unit of energy called a joule. A cal
T and q can have either negative or positive signs and Csp will always have a positive sign. The convention used is "q" has a positive value if heat is added to the substance from its surroundings and a negative value if the substance loses heat to its s
Changes of Physical State When the physical state of a substance is changed, heat is either absorbed or liberated but the temperature remains constant. The heat required to melt ice without any increase in the temperature of the system is equal to 80 calo
Nuclear Chemistry The nuclei of most naturally occurring elements are very stable in spite of the fact that the protons in the nucleus repel each other because of electrical repulsion. Some nuclei with certain ratios of neutrons to protons and nuclei with
Drawing Electron-Dot Formulas
Study the rules.
1. The first electron-dot formula we will try will be CH4
2. Now let's try a compound that has non-bonding electron pairs, H2O.
3. Next we should try an ion with a negative charge.
4. How about an ion with a
Common Question from students-What is the difference in the rubber band if it is made from plain rubber and polymers?
There can be many differences. There are many different types of polymers - rubber is also a polymer - so there can be many differences.
from students-Where does metal get its strength? I know that edges increase strength, and angles/folds help as well, but in terms of overall tensile strength versus thickness or number of angles/bends. -I am not sure I am following your qu
The general categories of materials are: 1.metals 2.ceramics 3.polymers 4.composites 5.semiconductors 6.biomaterials 7.nanotechnology and films
Possible midterm questions:
1. The whole chain of molecules is called a _. 2. _ is a material that is made from
Homework 1 Hint.
A company has asked you to help their business in space tourism. They have designed a rocket that will be powered by nitrous oxide (reacted with rubber), and you are to select materials for the fuel tank (pressure vessel). a) Considering
A material's structure determines its properties which in turn determine the applications for which it can be used. However, with knowledge of the structure and some creativity, the engineer can formulate a process that will change the structure and enhan
How does `Materials science' all relate? The fundamental science of materials looks at their structure and properties. Materials engineering is the processing and selection of materials. Materials science is an interdisciplinary field involving the proper
Naming Ionic Compounds We can learn the nomenclature of common ionic inorganic compounds by memorizing the following tables of common ions. Sometimes clusters of atoms are called groups and we learn a charge for the group as a whole. The order of the lett
Compounds Atoms of the same or different elements can combine in set proportions to form compounds. The proportions are determined by the numbers of electrons shared or exchanged between elements. This combining power of elements is most readily learned b
Those elements that are considered nonmetals are colored yellow. Those nonmetals that are the inert gases are colored light blue. The elements that are colored green are called metalloids and have some of the properties of metals as well as some of the pr
In the case of water, the three 2p orbitals of the oxygen atom are combined with the 2s orbital to form four sp3 hybrid orbitals. The two non-bonded electron pairs will occupy hybrid orbitals. Again we need a hybrid orbital for each atom and each pair of
Now let's look at something a bit different. In the boron trifluoride molecule, only three groups are arranged around the central boron atom. In this case, the 2s orbital is combined with only two of the 2p orbitals (since we only need three hybrid orbita
Finally let's look at beryllium dichloride. Since only two groups are attached to beryllium, we only will have two hybrid orbitals. In this case, the 2s orbital is combined with only one of the 2p orbitals to yield two sp hybrid orbitals. The two hybrid o
Hybridization Involving d-Orbitals
As we discussed earlier, some 3rd row and larger elements can accommodate more than eight electrons around the central atom. These atoms will also be hybridized and have very specific arrangements of the attached groups
Summary of Hybridization.In the following summary, groups are considered to be atoms and/or pairs of electrons and hybrid orbitals are the red lines and wedges. When the octet of an element is exceeded, then hybridization will involve dorbitals. Unhybridi
Hybridization Involving Multiple Bonds
Only a maximum of two electrons can occupy any orbital whether it is an atomic orbital or a molecular orbital due to electron-electron repulsion. When we draw a double or a triple-bond between two atoms, we imply tha
In the molecule C2H4, ethene, both carbon atoms will be sp2 hybridized and have one unpaired electron in a non-hybridized p orbital.
These p-orbitals will undergo parallel overlap and form one pi bond with beanshaped probability areas above and below the
The 3-dimensional model of ethene is therefore planar with H-C-H and H-C-C bond angles of 120o.the pi-bond is not shown in this picture.
Now let's look at H2C2 (acetylene). Both carbon atoms will be sp hybridized and have one electron in each of two unhyb
Electron-Pair Geometry and Molecular Geometry Now for a discussion about the shape of molecules! Why should you learn two ways to describe the geometry. When we experimentally look at molecules, we see how the atoms are arranged but don't see the non-bond
Let's see how this works by doing some examples. 1. First draw the electron-dot formula. 2. Then determine the hybridization needed for the number of groups attached to the central atom. 3. Now draw the 3-dimensional shape corresponding to that hybridizat
Balancing Chemical Equations Chemical equations must be balanced with respect to all atoms and the atoms must exist in real compounds.
Balance equations by using the following rules. 1. Select the compound with the largest number of atoms of an element no
The convention of writing acids always places the acidic hydrogen atoms first in the formula. Therefore you will always know that HF (aq), HCl (aq), HBr (aq), HI (aq) and nitric acid, HNO3, all have 1 acidic hydrogen atom. Sulfuric acid, H2SO4, has 2 acid