Search found 34 matches
- Mon Jun 04, 2018 4:38 pm
- Forum: Hybridization
- Topic: Meaning of hybridization
- Replies: 2
- Views: 417
Re: Meaning of hybridization
Carbon with its unhybridized atomic orbitals can only form 2 bonds because it only has 2 unpaired electrons (unpaired electrons are necessary to form bonds; just having an empty orbital doesn't let an atom form a bond). The overall purpose of hybridization is to lower the energy of the molecule over...
- Mon Jun 04, 2018 4:27 pm
- Forum: Bond Lengths & Energies
- Topic: Ionic Character
- Replies: 12
- Views: 15078
Re: Ionic Character
To respond to the two replies above, the first person is correct that a greater difference in electronegativities causes a greater ionic character. In the case of NaBr vs NaI, Na has a low electronegativity, I has a high electronegativity, and Br has an even higher electronegativity. Therefore, NaBr...
- Mon Jun 04, 2018 4:15 pm
- Forum: Hybridization
- Topic: Why # regions of e density= # atomic orbitals?
- Replies: 3
- Views: 498
Re: Why # regions of e density= # atomic orbitals?
The 4 hybrid orbitals (sp3) is just one example of how orbitals can hybridize. In a molecule like HCONH2, the carbon actually has 3 hybrid orbitals (sp2) because it has a single bond with hydrogen, a single bond with nitrogen, and a double bond with oxygen. In the double bond with oxygen, the sigma ...
- Thu May 31, 2018 5:56 pm
- Forum: Hybridization
- Topic: Hybridization
- Replies: 2
- Views: 443
Re: Hybridization
Hybridization has to occur for an atom to have the correct number of hybridized orbitals to make the correct number of bonds in a molecule. For example, carbon as an atom has a full 2s orbital, two 2p orbitals with unpaired electrons, and one empty 2p orbital. Therefore, it has 2 unpaired electrons ...
- Thu May 31, 2018 5:53 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: HW Question 4.25
- Replies: 1
- Views: 212
Re: HW Question 4.25
A molecule is polar if it has one or more polar bonds with dipoles that don't cancel. From the Lewis structure, you can infer that the C-Cl bonds are polar, but you can't determine if the dipoles cancel out until you determine the molecular shape. CH2Cl2 has the formula AX4, so it has a tetrahedral ...
- Thu May 31, 2018 5:46 pm
- Forum: Hybridization
- Topic: sp^3 orbitals
- Replies: 3
- Views: 390
Re: sp^3 orbitals
I agree with Nabila--empty orbitals can't form bonds, unpaired electrons in 2p3 orbitals form sigma bonds. You might be thinking about unhybridized p-orbitals, which form pi bonds.
- Thu May 31, 2018 5:42 pm
- Forum: Hybridization
- Topic: Why # regions of e density= # atomic orbitals?
- Replies: 3
- Views: 498
Re: Why # regions of e density= # atomic orbitals?
I think what you're referring to is the line from the lecture slide that "regions of e- density = number of hybrid orbitals". When hybridization occurs, atomic orbitals are mixed to become hybridized orbitals and electrons are redistributed among the hybridized orbitals. For example, when ...
- Fri May 25, 2018 10:24 pm
- Forum: Lewis Structures
- Topic: Why Resonance for SO2?
- Replies: 3
- Views: 3475
Re: Why Resonance for SO2?
I thought that for structures to have resonance, they had to have the same energy level. Does this mean resonant structures can have different levels of energy?
- Fri May 25, 2018 10:21 pm
- Forum: Bond Lengths & Energies
- Topic: bond length and charge
- Replies: 3
- Views: 2434
Re: bond length and charge
Bond length is also related to bond strength. The stronger the bond, the shorter it is. Single bonds are longer than double bonds which are longer than triple bonds.
- Fri May 25, 2018 10:14 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR
- Replies: 3
- Views: 379
Re: VSEPR
The number of bonds doesn't affect how you use the VSEPR model to draw molecular shapes. Single, double, and triple bonds are all treated as one region of electron density. Therefore, it doesn't matter which resonance structure you use to draw a molecular structure because you'll get the same result...
- Sat May 19, 2018 11:25 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal charge in (S2CO)2-
- Replies: 3
- Views: 4361
Re: Formal charge in (S2CO)2-
I think you're right, that it would be preferable (lower energy) to put the formal charges of -1 both on sulfur atoms, instead of one on sulfur and one on oxygen. I think that's why there's a > sign pointing towards the structure with the formal charges on sulfur--it means that structure is preferre...
- Sat May 19, 2018 11:13 pm
- Forum: Ionic & Covalent Bonds
- Topic: Bonds between 1.5 and 2 [ENDORSED]
- Replies: 5
- Views: 968
Re: Bonds between 1.5 and 2 [ENDORSED]
The numbers 1.5 and 2 are just guidelines. There are exceptions, like Mg-Cl bonds which have a difference in electronegativity of 1.85 but are ionic. For bonds between 1.5 and 2, it is just even harder to determine what type a bond is based solely on its electronegativity.
- Sat May 19, 2018 11:09 pm
- Forum: Dipole Moments
- Topic: Meaning of an induced dipole
- Replies: 3
- Views: 1832
Re: Meaning of an induced dipole
A dipole is a molecule with a positive charge on one end and a negative charge on the other. One example is H2O, which has a partial positive charge on the hydrogens and a partial negative charge on the oxygen. An induced dipole is when interactions between two molecules cause one or both of them to...
- Thu May 10, 2018 3:17 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Relationship between Electromagnetic Radiation and Enrgy of the photon
- Replies: 2
- Views: 404
Re: Relationship between Electromagnetic Radiation and Enrgy of the photon
Correct me if I'm wrong, but I think electromagnetic radiation has to do with the wave-like properties of light, and photons have to do with the particle-like properties of light. You can still use properties of electromagnetic radiation (like frequency, wavelength) to calculate the energy of photon...
- Thu May 10, 2018 3:04 pm
- Forum: Trends in The Periodic Table
- Topic: Relationship between Ionic Radius, Atomic RdiuIonization Enrgy, Electron Affinity
- Replies: 3
- Views: 920
Re: Relationship between Ionic Radius, Atomic RdiuIonization Enrgy, Electron Affinity
It's also important to remember that these are trends, not rules, so there are several exceptions that may break the patterns between them. For example, boron is to the right of beryllium in the periodic table, so its electron affinity is bigger but its ionization energy is smaller instead of larger...
- Thu May 10, 2018 2:57 pm
- Forum: Ionic & Covalent Bonds
- Topic: Difference between anions and cations?
- Replies: 3
- Views: 1639
Re: Difference between anions and cations?
I think you may have gotten mixed up about anions vs. cations. You're right that anions have a negative charge, but that's because they have gained an extra electron--remember that electrons have a negative charge so having extra electrons would make the atom more negative. Cations therefore have a ...
- Fri May 04, 2018 1:38 pm
- Forum: Trends in The Periodic Table
- Topic: Removing the 2nd electron is always harder [ENDORSED]
- Replies: 5
- Views: 1556
Re: Removing the 2nd electron is always harder [ENDORSED]
Removing the second electron is always harder because once you remove the first electron, the atom becomes a cation (positive charge) and will exert a greater electrostatic pull on its remaining electrons.
- Fri May 04, 2018 1:16 pm
- Forum: Properties of Electrons
- Topic: Exciting Electrons
- Replies: 2
- Views: 516
Re: Exciting Electrons
When the electron goes from 1s to 2p, its principal quantum number (n) goes from 1 to 2, meaning it goes from the first shell to the second shell. The shell directly corresponds to the size of the orbital, so a higher value of n means a larger size of atom.
- Fri May 04, 2018 1:14 pm
- Forum: Properties of Light
- Topic: Higher Work Function and Electron Velocity?
- Replies: 1
- Views: 1162
Re: Higher Work Function and Electron Velocity?
The work function is how much energy it takes to remove an electron from a metal, and the velocity of the removed electron depends on how much energy is left after being removed. The equation that relates these two concepts is: Energy of photon - work function = kinetic energy of electron, and kinet...
- Fri Apr 27, 2018 1:05 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Angular Momentum Quantum Numbers
- Replies: 1
- Views: 299
Re: Angular Momentum Quantum Numbers
You're right that the angular momentum quantum number describes shape. If l is 0, for example, the orbital is an s-orbital with a spherical shape. If l is 1, the orbital is a p-orbital. The n-1 is used to calculate what possible l values an orbital may have, based on its principal quantum number n. ...
- Fri Apr 27, 2018 1:01 pm
- Forum: Einstein Equation
- Topic: Hw problem 1.59 [ENDORSED]
- Replies: 3
- Views: 593
Re: Hw problem 1.59 [ENDORSED]
You're right that you have to use E = hc/lambda. Plugging in the constants for h, c, and the given wavelength for lambda will give you the energy per photon. Then you multiply by the given number of photons to get the total energy produced.
- Fri Apr 27, 2018 11:05 am
- Forum: Properties of Light
- Topic: Homework question 1.27 [ENDORSED]
- Replies: 3
- Views: 434
Re: Homework question 1.27 [ENDORSED]
Once you have the number of electrons emitted in 2 seconds, you can just divide that by Avogadro's constant to get the moles of electrons emitted in 2 seconds.
- Wed Apr 25, 2018 11:29 pm
- Forum: Einstein Equation
- Topic: Difference Between Equations [ENDORSED]
- Replies: 4
- Views: 836
Re: Difference Between Equations [ENDORSED]
Yes, they are just different pathways to solve for the same thing based on what information you are given.
This is because frequency (v) and wavelength (lambda) have an inverse relationship where v = c/lambda. So the two equations for energy are equivalent.
This is because frequency (v) and wavelength (lambda) have an inverse relationship where v = c/lambda. So the two equations for energy are equivalent.
- Fri Apr 20, 2018 9:38 am
- Forum: Properties of Light
- Topic: units for frequency and wavelength [ENDORSED]
- Replies: 9
- Views: 699
Re: units for frequency and wavelength [ENDORSED]
I have seen questions that asked for both frequency and wavelengths, or just one. If you have one but not the other, it is easy enough to convert between frequency and wavelength using v = c/lambda, so it doesn't really matter which order you find them.
- Fri Apr 20, 2018 9:35 am
- Forum: Photoelectric Effect
- Topic: 1.9
- Replies: 6
- Views: 469
Re: 1.9
I think what you calculated was actually frequency, not wavelength. In the equation E = hv, v stands for frequency so you would want to use E = hc/lambda and solve for lambda instead. A wavelength of 4.980x10^14 Hz seems more than reasonable. For reference, red light has a frequency of about 4.3x10^...
- Fri Apr 20, 2018 9:28 am
- Forum: Properties of Light
- Topic: 1.3 Atomic Spectra- Rydberg's equation
- Replies: 3
- Views: 384
Re: 1.3 Atomic Spectra- Rydberg's equation
Rydberg's equation is derived from the equation we used in class (E = -hR / n^2) with the main difference that Rydberg's equation has two n values, n1 and n2, so it can be used as a shortcut when you calculate the energy needed or released when transitioning between two energy levels. E = -hR / n^2 ...
- Sat Apr 14, 2018 3:54 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: 1.3 Atomic Spectra- Spectral lines
- Replies: 4
- Views: 243
Re: 1.3 Atomic Spectra- Spectral lines
That's right. They also use different values for n1 (Balmer series uses n1 = 2, Lymer uses n1 = 1).
- Sat Apr 14, 2018 2:26 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Line absorption spectrum vs. line emission spectrum [ENDORSED]
- Replies: 1
- Views: 157
Line absorption spectrum vs. line emission spectrum [ENDORSED]
What is the difference between a line absorption spectrum and line emission spectrum (if any), other than the fact that they measure light absorption vs. light emission? Would a line absorption spectrum for a particular element necessarily have the same wavelengths as its line emission spectrum?
- Sat Apr 14, 2018 12:38 am
- Forum: Photoelectric Effect
- Topic: Post module quiz #25
- Replies: 6
- Views: 315
Re: Post module quiz #25
Option A contains v (frequency of light), but c is the speed of light, not the energy of light. Option B has to do with kinetic energy. Option C is the equation we used in class, relating the energy of an incoming photon to the threshold energy needed to eject an electron and the resulting kinetic e...
- Sat Apr 14, 2018 12:22 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: 1.3 Atomic Spectra- Spectral lines
- Replies: 4
- Views: 243
Re: 1.3 Atomic Spectra- Spectral lines
n is used as a counting number, so it doesn't stand for anything in particular. It is just used to generate values of lambda. In the Balmer series, for example, the equation for lambda contains the variable n, which is specified to be 3, 4, and all whole numbers after that. That means for the first ...
- Sat Apr 14, 2018 12:17 am
- Forum: Properties of Light
- Topic: Light frequency and photons [ENDORSED]
- Replies: 2
- Views: 141
Re: Light frequency and photons [ENDORSED]
Increasing the frequency of light increases the energy each photon has. Due to the equation E = h * v, when v (frequency of light) increases, E (energy per photon) increases proportionally.
- Sat Apr 07, 2018 1:54 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: HW G.25
- Replies: 1
- Views: 179
Re: HW G.25
You're right that just diluting a solution doesn't change the total number of solute molecules in the solution, so after diluting the solution 90 times there is the same number of solute molecules you started with. But the question asks how many solute molecules would be present in 10. mL of the fin...
- Sat Apr 07, 2018 1:43 pm
- Forum: Limiting Reactant Calculations
- Topic: Video 3 Post- assessment
- Replies: 1
- Views: 159
Re: Video 3 Post- assessment
There was one partially confusing piece of information provided on that question that changed my answer the first time around--the molar mass provided for 3AgNO3 (169.88 g/mol) is for one mol of AgNO3, not 3. With that in mind: Find the moles of C6H9Cl3 by dividing its mass by mass per mole: 0.750g ...
- Fri Apr 06, 2018 1:42 pm
- Forum: Significant Figures
- Topic: Questions F11
- Replies: 4
- Views: 522
Re: Questions F11
I was confused about this too. Since the mass percent compositions and mass of O2 are given to 3 sfs, wouldn't the answer have to have 3 sfs, not 4?