CH 101 1st Edition Exam 2 Study Guide Lectures 9 14 Lecture 9 February 2 How do I find the electron configuration of ions and Oxidation States Look at the electron configuration of the element found by looking at the periodic table and counting the number of element in each block orbital you go through to get to the element in question while moving left to right then if the ion is a cation subtract electrons from the element s orbitals in the order of p s d f unless the p orbital is filled then take electrons out of the s orbital If the ion is an anion add electrons to the atom starting with the lowest orbital This may result in having all orbitals filled here you would just write the noble gas that is equal to the electron configuration of the ion Find the oxidation state of atoms in a molecule by knowing the 6 rules Rule 1 The oxidation state of an element is always 0 F 0 H2 0 O8 0 Rule 2 The oxidation number of Fluorine F2 is always 1 Rule 3 The oxidation number of any element in Group 1 is always 1 K 1 Li 1 The oxidation number of any element in Group 2 is always 2 Ca 2 Ba 2 The oxidation number of Aluminum Al is always 3 Rule 4 The oxidation number of Hydrogen changes depending on who it bonds with a metal or a nonmetal When bonded to a metal the oxidation number of H is 1 When bonded to nonmetals its 1 Rule 5 The oxidation number of Oxygen O is always 2 Rule 6 The oxidation number of the elements in Group 17 halogens is most commonly 1 This rule is only used once all the other rules have been applied to the compound If you are given a picture of a complex molecule and asked to find the oxidation state of one of the atoms you will approach the problem differently by using the electron counting method In this situation keep in mind that the more electronegative atom is going to hog or possess both of the electrons in a bond First find the most common oxidation state by looking at the group number of the element then subtract the electron that atom possesses including lone pairs This will give you the oxidation number Lecture 10 February 4 What are the methods for naming different types of molecules I classify the naming of molecules by what type of bonds they have Type here Monoatomic anions always end in ide oxide nitride Ionic bonds always end in ide Carbon Oxide Lithium Bromide Covalent bonds take on the ending ide as well as the prefix mono di tri tetra penta hexa hepta octa nona deca depending on how many atoms of that element are in the molecule Dinitrogen pentoxide carbon monoxide Ionic bonds with Transition Metals end in ide because they are atomic bonds but they also use roman numerals to represent the charge of the transition metal Thallium III Bromide Nickel II Sulfite The charge is found by seeing how many electrons were given to the anion for example the charge of Nickel in NiSO3 is 2 because we know the polyatomic ion SO32 has a 2charge that must have been filled by two electrons from the nickel since the molecule doesn t look like Ni2 SO3 Polyatomic ions bonds between more than two atoms can end in ite ate or something abstract They can also start with per hypo or something else that s why it is easiest to just memorize them However you can also figure out the names of polyatomic ions using these steps If the cation s oxidation number is two less than the group number it ends in ite The group number for nitrogen is 5 the oxidation number for nitrogen in NO2 is 3 making it Nitrite Example SO32 Sulfite ClO21 Chlorite If an oxygen is taken away from the compound decreasing the oxidation level you add the prefix hypo to the name of the compound ClO1 Hypochlorite A compound will end in ate if the oxidation number of the cation is equal to it s main group number Sulfur s group number is 6 in the polyatomic ion SO42 the oxidation state of Sulfur is 6 and therefore we call this compound sulfate If you are given a compound with the ending of ite when you add one more oxygen to this compound you will get the compound with the ending ate Sulfite SO32 and Sulfate SO4 2 If you add another oxygen to any compound with the ending ate you must add the prefix per along with the ending ate this is the highest oxidation state of the compound For example Chlorate ClO31 and Perchlorate ClO41 Lecture 11 February 6 What is polarity and formal charge How do I draw Lewis Dot Structures Polarity is the pulling of electrons toward a certain direction based of electronegativity Determining polarity between molecules requires you to estimate based on their location on the periodic table The farther away elements are from each other the more polar they will typically become Formal charge is found by assuming a bond gives one electron to each atom it is bonding Formal charge The group number of the atom the number of possessed electrons including lone pairs To draw Lewis Dot Structures find the ER VE SP and LP then apply the bonds and lone pairs to the atoms Lecture 12 February 9 How to I choose the Preferred Resonance Structure and find Bond Order The preferred resonance structure will be the structure that where the charge is equal to that of the molecule and the more electronegative atom gets the charge in the case of an ion Bond Order is found through the equation of total bonds of bond regions where a one pair counts as a bonding region When you are trying to determine the bond order of a particular part of a molecule first look at the bond then determine if the atoms bonded are bonded to the same element in another bond like O C O If she points out the bond highlighted in red and asks for the bond order you would see if the carbon in bonded to another oxygen or if the oxygen is attached to another carbon Since the carbon is attached to another oxygen the number of bonds is 2 and the number of regions is 2 therefore the bond order is 2 2 1 Lecture 13 February 11 How do I identify Pi and Sigma bonds How do I remember hybridization Sigma bonds are the electron density between atoms this is the first bond atoms make between each other Sigma bonds are stronger than Pi bonds and are made from hybridized orbitals After a sigma bond is made between an atom they form Pi bonds Electron density above and below atoms every second or third bond is a Pi bond Pi bonds are weaker because their bonds are made between more electrons that are farther from the nucleus and are in the shape …