Summary - chapters 7-11 PDF

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Chapter 7 Dissociation 

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In order for a compound to dissociate its ions in water completely, it must: o be a strong electrolyte.  not a solid, liquid, or gas  must be aqueous  all soluble ionic compounds are strong electrolytes  all strong acids are strong electrolytes  HCl  HClO4  HI  H2SO4  HBr  HNO3 All polyatomic groups stay together in dissociation. Compounds that are always soluble in water are Li, Na, K, NH4, NO3, C2H3O2, ClO4 Compounds that may or may not be soluble in water depending on their partner are Cl, Br, I, and SO4^2-. Exceptions for Cl, Br, and I are Ag, Hg, and Pb. Exceptions for SO4^2- are Ca, Pb, Ba, Sr.

Precipitates   

If there is no precipitate formed, there is no reaction. The precipitate is the solid in the products of a reaction If the products of the reaction are all aqueous, there is no precipitate

Molecular versus Complete Ionic versus Net Ionic equations    

A molecular equation shows the complete, neutral formulas for every compound in a reaction; no clear picture of what actually happens in the reaction A complete ionic equation shows all of the species as they are actually present in the solution (separates out the ions) A net ionic equation shows only the species that actually participate in the reaction; shows what actually goes down; no spectator ions are included; product will be the precipitate Spectator ions are those ions that do not participate in the reaction; spectator ions will not be solids because those participate

Acids and Bases     

Acid-base reactions are also called neutralization reactions because the acid and the base neutralize each other’s properties. Acid-base reactions form water Acid- donates H+ ions in aq solutions Base- produces OH+ ions in aq solutions The H+ from the acid combines with the OH- from the base to form O(OH) or H2O

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The cation from the base combines with the anion to make a salt. So in an acid-base reaction, our products are a salt and water a strong base is a metal hydroxide (a metal and OH) that is completely soluble in water, giving separate OH- ions and cations o example: NaOH(s)  Na+(aq) + OH-(aq) o KOH  K+(aq) + OH-(aq) A strong acid completely dissociates Common strong acids are aqueous in solutions of: HCl, HBr, HI, H2SO4, HClO4, HNO3

Oxidation-reduction reactions 

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They occur whenever one of the following happens o A transfer of electrons (Zn+ Cu^2  Zn^2 + Cu) o A metal cation changes its charge (CuCl + FeCl  FeCl2 + CuCl2) o Elements combine to form a new compound o A compound is broken down to form one or more elements o O2 is one of the reactants (combustion) Combustion reactions o Reactions where O2 is a reactant o Release lots of energy o Part of redox reactions o Predicting products:  Contains C CO2(g)  Contains H H2O(g)  Contains S SO2(g)  Contains N NO2(g)  Contains metal M2On(s) Gas evolution reactions o Type of redox reaction o Some reactions form a gas directly from the ion exchange o Others forms a gas by the decomposition of one of the ion exchange products into gas and water

Classifying all these reactions… 

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Based on process o Precipitation rxn: a solid substance is formed o Neutralization rxn (acid-base): a neutral substance is formed (H2O) o Redox rxn: electron transfer occurred o Gas evolution rxn: a gaseous substance is formed Based on what atoms do o Synthesis or combination  obvi  A+BAB o Decomposition  Breaks apart

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 ABA+B  Only one reactant Single displacement  Single switcharoo  A+BCAC+B  Think about why it is called displacement. Notice what is being displaced. Double displacement  double switcharoo  AB+CDAD+CB  Think about why it is called displacement. Notice what is being displaced.

CHE 1300 Chapter 11 Outline Nuclear model of atom  

Atom has a small dense nucleus The rest of the atom is mostly empty space

Energy levels of atoms 

Energy levels of all atoms are quantized (like a set of stairs, not a ramp)

Q: when an electron is excited in an atom or ion a. Only specific quantities of energy are released in order for the electron to return to its ground state b. White light is never observed when the electron returns to its ground state c. The electron is only excited to certain energy levels d. All of the above The Bohr model of the atom (aka planetary model)     

Quantized energy levels Electron moves in a circular orbit Electron jumps between levels by absorbing or emitting a photon of a particular wavelength Erred in its assertion that an electron could be located in a precisely defined orbit Model is now only applied to the Hydrogen atom

The Wave Mechanical Model of the Atom    

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Doesn’t try to precisely describe the location or path of electrons Instead of circular orbits, the location and energy of electrons moving around the nucleus is specified using the three terms shell, subshell, and atomic orbital Orbital is not the same as orbit Atomic orbital or probability map o Shows where the electron is likely to be roughly 90%-95% o The probability of finding an electron decreases at greater distance from the nucleus Number (1,2,3,4,5…) o Indicates the shell o Indicates the energy level Letter (s,p,d,f,g,h,I,j,k…) o Indicates the subshell S subshells have 1 orbital-therefore 2 electrons P subshells have 3 orbitals- therefore a total of 6 electrons D subshells have 5 orbitals- therefore a total of 10 electrons F subshells have 7 orbitals- therefore a total of 14 electrons ground state- the lowest energy orbital an electron can occupy excited state- higher energy orbitals

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Principles of the Wave Mechanical Model (FOR TRUE OR FALSE Q) o Atoms have series of energy levels call principal or main energy levels or shells o The energy of the level increases as the value of n increases o Each principal energy level contains one or more types of orbitals, called sublevels or subshells o The number of sublevels present in a given principal energy level equals n o The orbitals are labelled by the n value of a given main shell followed by a letter that indicates the subshell (shape) of the orbital o An orbital can be empty or it can contain 1 or 2 electrons, but never more than two. If two electrons occupy the same orbital, they must have opposite spins o The shape of an orbital does not indicate the details of electron movement. It indicates the probability distribution for an electron residing in that orbital.

Electron Configuration o

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Pauli Exclusion Principle  Each orbital may have a maximum of 2 electrons  When 2 electrons are in the same orbital, they have opposite spins Aufbau principle  As protons are added one by one to the nucleus to build up the element, electrons are added to the orbital.  Electrons are filled in the energy shells and subshells in order of increasing energy (low to high)  How to know which orbital has lower energy:  Use the n + l rule where n=main energy level and l=sublevel value (s=0, p=1, d=2, f=3)  Lower n+l means lower energy

Aufbau Example: Using the n+l rule, which of the orbitals in each pair has lower energy? a. b. c. d.

3s or 3p 4d or 5s 6s or 4f 5d or 6p

Using the n+l rule, which of the orbitals in each pair will be occupied by electrons first? a. b. c. d.

3s or 3p 4d or 5s 6s or 4f 5d or 6p

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Hund’s Rule (Maximum Multiplicity)  Atom tends to have as many unpaired electrons as possible

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When orbitals of identical energy (called degenerate orbitals) are available, electrons occupy these orbitals singly rather than in pairs

Concept check: -

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How many unpaired electrons does the element cobalt have in its lowest energy state? a. 0 b. 2 c. 3 d. 7 Can an electron in a phosphorous atom ever be in a 3d orbital? Choose the best answer. a. Yes. an electron can be excited into a 3d orbital b. Yes. a ground-state electron in phosphorous is located in a 3d orbital c. No. only transition metal atoms can have electrons located in the d orbitals d. No. this would not correspond to phosphorous; electron arrangement in its ground state.

Valence Electrons and Core Electrons    

Valence electrons: The electrons in all the subshells with the highest principal energy shells Core electrons: electrons in lower energy shells Valence electrons are responsible for the chemical reactivity For transition and inner transition elements, valence electrons include electrons in the highest n and electrons in the incompletely filled d or f orbital

Ex. Rb- 37 electrons--1s22s22p63s23p63d104s24p65s1 The highest principal energy shell containing electrons is the 5th. So Rb has 1 valence electron and 36 core electrons Ex. Kr-36 electrons--1s22s22p63s23p63d104s24p6 The highest principal energy shell containing electrons is the 4th. So Kr has 8 total valence electrons and 28 core electrons Practice: -

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Z= 33, therefore ___ electrons o Electron configuration: ________________________ o Highest occupied principal energy level (n) = _______ o Valence electrons are _____________ o Total valence electrons= _____ Given the electron configuration, determine the number and type of valence electrons in Lithium-1s2 2s1 a. 1 electron, 1s1 b. 2 electrons, 1s2 c. 1 electron 2s1 d. 3 electrons 1s1 2s1 Given the electron configuration, determine the number and type of valence electrons in potassium- 1s2 2s2 2p6 3s2 3p6 4s1

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a. 19 electrons, 1s2 2s2 2p6 3s2 3p6 4s1 b. 9 electrons 3s2 3p6 4s1 c. 10 electrons, 1s2 2s2 2p6 d. 1 electrons 4s1 Lithium- 1s2 2s1- 1 valence electron (2s1) Period: Group: ___ A

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Potassium- 1s2 2s2 2p6 3s2 3p6 4s1- 1 valence electron (4s1) Period: Group: __ A

Orbital Filling 1. In a principal energy level that has d orbitals, the s orbital from the next level fills before the d orbitals in the current level 2. After Lanthanum, which has the electron configuration [Xe] 6s2 5d1, a group of 14 elements (lanthanides) occurs. These elements correspond to the filling of the seven 4f orbitals 3. After actinium, which has the electron configuration [Rn] 7s2 6d1, a group of 14 elements called the actinides occurs. These elements correspond to the filling of the seven 5f orbitals. 4. Except for He, the group numbers indicate the sum of electrons in the ns and np orbitals in the highest principal energy level that contains electrons. These electrons are the valence electrons. Noble Gas Configurations Examples: Rb- [Kr]5s1 Mg- [Ne]3s2 Fe- [Ar]4s2 3d6 Ga- [Ar]4s2 3d10 4p1 Br- [Ar]4p5 Bi- [Xe]6s2 5f14 5d10 6p3     

Noble gases have 8 valence electrons (except for He which has 2) Noble gases are non-reactive because they are especially stable in their configuration Alkali metals are the most reactive because they are one electron away from a stable outer shell In their reactions, alkali metals tend to lose their extra electron, resulting in the same electron configuration as the previous noble gas (and forming a cation with a +1 charge) Amongst the nonmetals, halogens are the most reactive. They are also only one electron away from a noble gas. Halogens tend to gain and electron in their reactions. Forms an anion with a -1 charge.

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When halogens react with other nonmetals, they tend to share electrons so that each attains the configuration of a noble gas Ex. Anions: O, 8 electrons: 1s2 2s2 2p4 O^2-, 10 electrons: 1s2 2s2 2p6 Cl, 17 electrons: 1s2 2s2 2p6 3s2 3p5 Cl-, 18 electrons: 1s2 2s2 2p6 3s2 3p6 Cations: Na, 11 electrons: 1s2 2s2 2p6 3s1 Na+, 10 electrons: 1s2 2s2 2p6 K, 19 electrons: 1s2 2s2 2p6 3s2 3p6 4s1 K+, 18 electrons: 1s2 2s2 2p6 3s2 3p6

Isoelectronic: having the same number of electrons (ex. O^2-, Ne, Na+, Mg^2+)...