Search found 51 matches
- Wed Dec 04, 2019 1:49 pm
- Forum: Lewis Acids & Bases
- Topic: Oxoacids
- Replies: 6
- Views: 432
Re: Oxoacids
An oxoacid is an acid that has oxygen bonded to a hydrogen atom, along with another element. This bond is able to be dissociated so the hydrogen atom can be donated.
- Wed Dec 04, 2019 1:44 pm
- Forum: Lewis Acids & Bases
- Topic: Definition
- Replies: 7
- Views: 583
Re: Definition
A Lewis acid accepts electron pairs while a Lewis base donates electron pairs.
- Wed Dec 04, 2019 1:42 pm
- Forum: Lewis Acids & Bases
- Topic: charges of transitional metals
- Replies: 3
- Views: 206
Re: charges of transitional metals
I would assume that either it would be given if we needed it or we would be able to calculate it through the charges of the ligands of the coordination compound.
- Wed Dec 04, 2019 1:41 pm
- Forum: Lewis Acids & Bases
- Topic: HCl and HI
- Replies: 10
- Views: 595
Re: HCl and HI
HI is a stronger acid because it has a longer bond length so its bond is weaker, thus it is easier for the bond to be broken to donate the H+ compared to HCl.
- Wed Dec 04, 2019 1:28 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Acid or Base
- Replies: 2
- Views: 191
Re: Acid or Base
In general, nonmetal oxides are acidic, metal oxides are basic, and semimetal oxides are amphoteric. Sulfur is a nonmetal so it is acidic.
- Thu Nov 28, 2019 1:49 am
- Forum: Naming
- Topic: Alphabetical Order
- Replies: 6
- Views: 411
Re: Alphabetical Order
You name a coordination compound by listing the ligands in alphabetical order, disregarding the prefix, and then the metal, with -ate if the coordination compound is negatively charged.
Re: Oxidation
The oxidation number is the charge the atom would have if the compound was composed of ions. It is the number of electrons gained or loss to form a bond.
- Thu Nov 28, 2019 1:43 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Cis vs Trans
- Replies: 22
- Views: 1803
Re: Cis vs Trans
Cis molecules are polar while trans molecules are nonpolar because of the ligand positioning either on the same or opposite side.
- Thu Nov 28, 2019 1:39 am
- Forum: Naming
- Topic: Naming coordination compound
- Replies: 3
- Views: 246
Re: Naming coordination compound
The textbook says to list the ligands alphabetically but I think the convention is to put the neutral ligands first and then the anionic ligands.
- Thu Nov 28, 2019 1:37 am
- Forum: Naming
- Topic: Ligand Order
- Replies: 5
- Views: 375
Ligand Order
When writing the molecule formula for the coordination compound, should the neutral or negative ligand go first? Here, Dr. Lavelle says to put the anionic ligand first but I think what is conventional has changed since then but I'm not sure: https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=45&...
- Wed Nov 20, 2019 11:50 am
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Condition for pi bond
- Replies: 4
- Views: 336
Re: Condition for pi bond
There will not be pi bonds without sigma bonds. A pi bond only occurs for double and triple bonds, where there is 1 sigma bond.
- Wed Nov 20, 2019 11:48 am
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Sigma and Pi Bonds
- Replies: 12
- Views: 1103
Re: Sigma and Pi Bonds
DLee_3C wrote:So is the pi bond both the top and bottom electron areas? or are they both separate pi bonds?
They are separate pi bonds. There are 2 pi bonds and 1 sigma bond in a triple bond.
- Wed Nov 20, 2019 11:46 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Seesaw Shape
- Replies: 12
- Views: 676
Re: Seesaw Shape
The bond angles would be <90, <120, and >180 degrees because the lone pair has a stronger repulsive force than the bond.
- Wed Nov 20, 2019 11:44 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: cancelling dipoles
- Replies: 2
- Views: 198
Re: cancelling dipoles
At least based on what we have learned so far, you are right that dipoles only cancel for a tetrahedral if all the atoms bonded to the central atom are the same. With different atoms in the tetrahedral shape, symmetry is impossible so the molecule would probably be polar.
- Wed Nov 20, 2019 11:37 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pairs for AX4E
- Replies: 3
- Views: 199
Re: Lone Pairs for AX4E
If the lone pair was on the axial plane, it would have a 90 degrees bond angle with 3 atoms. With the lone pair on the equatorial plane, it would have a 90 degrees bond with only 2 atoms. There is less repulsion by putting the lone pair on the equatorial plane so it should be there.
- Wed Nov 13, 2019 11:28 pm
- Forum: Dipole Moments
- Topic: Can nonpolar molecules with polar bonds have dipole dipole interactions?
- Replies: 4
- Views: 353
Can nonpolar molecules with polar bonds have dipole dipole interactions?
A molecule like H2SeO4 has hydrogen bonds right? And hydrogen bonds are dipole dipole forces?
- Tue Nov 12, 2019 4:00 pm
- Forum: Bond Lengths & Energies
- Topic: Shorter bond lengths
- Replies: 12
- Views: 725
Re: Shorter bond lengths
With more electrons being involved in the bond, the strength of the pulling attraction is stronger thus the bond length is shorter.
- Tue Nov 12, 2019 3:58 pm
- Forum: Dipole Moments
- Topic: Dipole Moment
- Replies: 6
- Views: 347
Re: Dipole Moment
A molecule has a dipole moment if there is an unequal sharing of electrons. The arrow points towards the delta negative not delta positive since that is where the electron is being pulled towards.
- Tue Nov 12, 2019 3:50 pm
- Forum: Dipole Moments
- Topic: Dipoles
- Replies: 2
- Views: 132
Re: Dipoles
Dipoles occur from the difference in electronegativity between 2 ions causing an unequal sharing of electrons. The dipole moment measures the polarity of the molecule.
- Tue Nov 12, 2019 3:46 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Dipole moment
- Replies: 4
- Views: 301
Re: Dipole moment
A dipole moment is a vector measurement of the separation of two opposite electrical charges, calculated by the charge multiplied by the distance between the charges. It comes from a difference in electronegativity between 2 ions and measures the polarity of a molecule.
- Tue Nov 12, 2019 3:34 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: central atoms
- Replies: 7
- Views: 384
Re: central atoms
You are right that the atom with the lowest ionization energy is the central atom. In that example, oxygen has a higher electronegativity than chlorine so chlorine is the central atom.
- Mon Nov 04, 2019 1:50 pm
- Forum: Lewis Structures
- Topic: Lewis Structure
- Replies: 4
- Views: 289
Re: Lewis Structure
The element with the lowest ionization energy goes in the center of the Lewis structure. Ionization energy decreases down a group and increases across a period.
- Mon Nov 04, 2019 1:48 pm
- Forum: Resonance Structures
- Topic: Showing resonance
- Replies: 8
- Views: 399
Re: Showing resonance
You would show resonance by drawing all of the possible Lewis diagrams with the lowest formal charges for the molecule and then by drawing a double-ended arrow between the structures. The double-ended arrow shows resonance between the structures.
- Mon Nov 04, 2019 1:45 pm
- Forum: Resonance Structures
- Topic: Bond lengths
- Replies: 11
- Views: 423
Re: Bond lengths
In reality, the molecule is a resonance hybrid and is a combination of all of the resonance structures. This results in a bond length between a single and double bond since the bonds are defined as neither a single bond nor a double bond.
- Mon Nov 04, 2019 1:42 pm
- Forum: Resonance Structures
- Topic: Resonance Structure
- Replies: 2
- Views: 235
Re: Resonance Structure
For drawing resonance structures, you would draw every possible Lewis structure with the lowest formal charges that could represent the molecule. Resonance structures are denoted with a double-ended arrow.
- Mon Nov 04, 2019 1:38 pm
- Forum: Resonance Structures
- Topic: Octet
- Replies: 13
- Views: 869
Re: Octet
The octet rule says that elements like to bond so that each element has 8 electrons in its valence shell. Exceptions include H, He, and Li.
- Wed Oct 30, 2019 2:03 am
- Forum: Lewis Structures
- Topic: Formal Charge [ENDORSED]
- Replies: 6
- Views: 189
Re: Formal Charge [ENDORSED]
Formal charge is the charge assigned to an atom assuming the electrons are shared equally. You calculate formal charge with the equation FC = V - (L + S/2) where FC = formal charge, V = valence electrons, L = lone pair electrons, and s = shared electrons of that specific atom.
- Wed Oct 30, 2019 2:00 am
- Forum: Lewis Structures
- Topic: Formal Charge
- Replies: 2
- Views: 108
Re: Formal Charge
The S in the equation is for shared electrons. For each bond between 2 atoms, there are 2 shared electrons. So if there exists a triple bond, there are a total of 6 shared electrons for those atoms.
- Wed Oct 30, 2019 1:57 am
- Forum: Lewis Structures
- Topic: Resonance
- Replies: 4
- Views: 119
Re: Resonance
Resonance is when there are multiple ways of describing bonds through the structure, and thus in real life it is a combination of these contributing structures.
- Wed Oct 30, 2019 1:54 am
- Forum: Lewis Structures
- Topic: Drawing lewis structures
- Replies: 8
- Views: 293
Re: Drawing lewis structures
So far, we have not covered bond angles yet so I would assume it is not to be expected from us unless Dr. Lavelle goes over it in a future lecture.
- Mon Oct 28, 2019 9:53 pm
- Forum: Ionic & Covalent Bonds
- Topic: How to count valence electrons with the d block
- Replies: 4
- Views: 373
How to count valence electrons with the d block
For example for 3d, would an element like Mn have 2 or 7 valence electrons? Would Cu have 1 or 11 valence electron? I'm pretty sure that Ga has 3 valence electrons right? Can someone explain when 3d is included in valence electrons?
- Mon Oct 21, 2019 3:33 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Are electrons always removed from the 4s orbital before the 3d orbital?
- Replies: 6
- Views: 634
Are electrons always removed from the 4s orbital before the 3d orbital?
I know the 4s orbital fills first before the 3d orbital because the 4s orbital is lower in energy, but are electrons always removed from the 4s orbital first as well?
- Mon Oct 21, 2019 3:29 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Why is 4s before 3d?
- Replies: 9
- Views: 1011
Re: Why is 4s before 3d?
The 4s orbital initially has lower energy than the 3d orbital so according to the Aufbau principle it would fill first. However, as the 3d orbital is filled it begins to have less energy than the 4d orbital so electrons are removed from the 4d orbital.
- Mon Oct 21, 2019 3:15 pm
- Forum: Trends in The Periodic Table
- Topic: 1st and 2nd Ionization
- Replies: 5
- Views: 295
Re: 1st and 2nd Ionization
Ionization energy is just the minimum amount of energy needed to remove an electron from a gaseous atom. The second ionization energy is always larger than the first ionization energy because there is a stronger nuclear charge once an electron is already missing.
- Mon Oct 21, 2019 2:35 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Nodal Plane Significance
- Replies: 2
- Views: 101
Nodal Plane Significance
I know that nodal planes are areas where the probability of finding electrons is 0 and that they depend on the orbital. Is there more significance to these planes or do we just need to memorize the shapes of orbitals?
- Mon Oct 21, 2019 1:32 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Exceptions (Cr and Cu)
- Replies: 3
- Views: 155
Exceptions (Cr and Cu)
I know that Dr. Lavelle mentioned that Cr and Cu are exceptions to the rules and have electron configurations of [Ar] 3d5 4s1 and [Ar] 3d10 4s1 respectively. Does this extrapolate to the whole group 6 and group 11 where an electron is always taken from the 4s orbital?
- Mon Oct 14, 2019 2:51 pm
- Forum: Einstein Equation
- Topic: 1B.15 c)
- Replies: 3
- Views: 228
Re: 1B.15 c)
Part a asks for the wavelength of the ejected electron which can be found using the kinetic energy of the ejected electron and E = hv and c = vλ. Part c asks for the wavelength of the proton that caused the electron to be ejected which would be solved in a similar fashion after finding the energy of...
- Mon Oct 14, 2019 2:34 pm
- Forum: Einstein Equation
- Topic: Einstein Equation
- Replies: 4
- Views: 259
Re: Einstein Equation
The equation comes in handy whenever you need to find the energy of a photon if you know the it's frequency, or vice versa. In a lot of photoelectric effect problems, often you will need to use E = hv first to find the energy of the photon in order to solve for the other components of the problem.
- Mon Oct 14, 2019 2:31 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Indeterminancy In Class
- Replies: 7
- Views: 265
Re: Indeterminancy In Class
Heisenberg's indeterminacy equation was simply mentioned Friday and is explained a lot more in-depth today in lecture. There is also a module on Heisenberg's indeterminacy equation on Dr. Lavelle's website if you want more explanation or practice on the subject.
- Mon Oct 14, 2019 2:27 pm
- Forum: DeBroglie Equation
- Topic: Diffraction patterns
- Replies: 4
- Views: 225
Re: Diffraction patterns
Constructive interference occurs when two waves are in phase and "add" to each other. This happens when both waves are positive or negative at the same time so their amplitudes will increase after they collide. Destructive interference is the opposite and occurs when two waves are out of p...
- Mon Oct 14, 2019 2:19 pm
- Forum: Properties of Light
- Topic: What is Threshold Energy?
- Replies: 9
- Views: 760
Re: What is Threshold Energy?
Threshold energy is the least amount of energy needed to eject an electron off of a surface. Threshold energy is important when using Einstein's photoelectric equation since it is one of the three components of his equation: E(photon) - E(threshold) = E(kinetic).
- Wed Oct 09, 2019 1:52 pm
- Forum: Empirical & Molecular Formulas
- Topic: Empirical Ratio Rounding
- Replies: 6
- Views: 800
Re: Empirical Ratio Rounding
If it is 0.8, I believe you would have to multiply all of the elements of the compound by 5 in order to find the empirical formula since that is the smallest number you can multiply by to get a whole number. Rounding 0.8 to 1 is a bit of a stretch even if you rounded in your work.
- Wed Oct 09, 2019 1:48 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Concentration Calculation
- Replies: 2
- Views: 188
Re: Concentration Calculation
First, you would add the convert the grams of the 2 solutes to moles using the molar masses. Then, add those 2 moles to find the total moles of solute. Finally, divide the moles of solute by the volume of the solution in order to find the molarity and compare that to 5.30 x 10^-3 M to see whether or...
- Wed Oct 09, 2019 11:50 am
- Forum: Balancing Chemical Reactions
- Topic: Conservation of electrons/protons
- Replies: 7
- Views: 736
Re: Conservation of electrons/protons
Electrons and protons have mass as well so based off of the law of conservation of mass, the number of electrons and protons must stay the same in a chemical equation. That's just one way to think about it, because there's also charge conservation as well.
- Wed Oct 09, 2019 11:47 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Conserved in Chem Rxn
- Replies: 5
- Views: 524
Re: Conserved in Chem Rxn
You're right that mass and the number of atoms are conserved. Electrons and protons are also conserved because remember that they have mass as well. If the equation were to gain or lose electrons or protons then the mass wouldn't be balanced between the 2 sides of the equation.
- Wed Oct 09, 2019 11:26 am
- Forum: Balancing Chemical Reactions
- Topic: How to write reactions for tests
- Replies: 5
- Views: 236
Re: How to write reactions for tests
I don't think he ever mentioned knowing the states so I wouldn't be too worried about including them. Obviously if they're given in the unbalanced chemical equation you should keep it in your work, but in general I don't think we are writing our own chemical equations from the names of chemical comp...
- Wed Oct 09, 2019 12:45 am
- Forum: SI Units, Unit Conversions
- Topic: How to express answers
- Replies: 13
- Views: 531
How to express answers
I just switched into this class and was wondering if Dr. Lavelle ever mentioned how he wanted answers formatted. Are we supposed to use scientific notation or SI prefixes or does it not matter?
- Wed Oct 09, 2019 12:42 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Homework for Week 2
- Replies: 4
- Views: 322
Re: Homework for Week 2
I doubt TA's are spending the time to record exactly what questions everyone has done so I wouldn't be too stressed about it. However, these problems are for practice so you should be a little more conscious with the questions you work on and be sure that they are helping you learn the material cove...
- Wed Oct 09, 2019 12:37 am
- Forum: Balancing Chemical Reactions
- Topic: Subscripts [ENDORSED]
- Replies: 3
- Views: 225
Re: Subscripts [ENDORSED]
Changing the subscript would change the molecule. The chemical equation has specific molecules and changing them would result in a totally different chemical equation. Any differences in the solutions manual should be a typo or misprint since the only things you can change in order to balance chemic...
- Wed Oct 09, 2019 12:26 am
- Forum: Significant Figures
- Topic: Significant figures on the periodic table
- Replies: 3
- Views: 139
Re: Significant figures on the periodic table
Just using all of the significant digits provided by the periodic table would be the best, which for the periodic table provided to us is only 3-4 decimal places depending on the element. I believe in class Dr. Lavelle usually uses 4 decimal places as well to solve problems.
- Wed Oct 09, 2019 12:17 am
- Forum: Significant Figures
- Topic: Are we allowed to round when showing work?
- Replies: 7
- Views: 539
Are we allowed to round when showing work?
Let's say I didn't have one long line of dimensional analysis and instead first found one number before later using it again to calculate a final answer. Is it fine to show my work as rounded, even if I keep it exact in my calculator?