CHEMISTRY COMMUNITY

Kelvin Chung 1C

Since oxygen is more electronegative than nitrogen, it is less likely to share its electrons with a proton. Thus, the nitrogens are able to accept protons while the oxygens are not.

Kelvin Chung 1C

I know oxalate is primarily bidentate, but can it also be a monodentate? Or does the binding of one oxygen atom on oxalate cause an adjacent oxygen to bind to the central metal atom as well due to proximity?

Kelvin Chung 1C

When the ligand binds to a central metal atom at two or more of its sites, it is considered a polydentate. You can tell where these sites are by looking for lone pairs. Usually I look for oxygens and nitrogens in the ligand to see if they have any lone pairs they can donate. The shape of the ligand ...

Kelvin Chung 1C

NH4I is a salt, so there isn't a conjugate acid or base. You can find which acids or bases it is derived from though, which is NH4+ and I - If you look at the other parts of the same question, there are salts, but the conjugate acid and base are easily identifiable. In part a) NH 4 I (aq) +...

Kelvin Chung 1C

I know this question doesn't ask for a conjugate acid or base, but I was just curious what they would be in this chemical reaction. 6A.9 c) NH 4 I (am) + KNH 2 (am) --> KI (am) + 2NH 3 (l) "am" indicates that liquid ammonia is the solvent The textbook's use ...

Kelvin Chung 1C

Can someone explain why when C double bonds to another C as in ethylene, the pi bond is a bond between the C's unhybridized 2p orbitals?

Kelvin Chung 1C

Dr. Lavelle also said in class that the shape of certain ligands make it easier for them to chelate. For example, although ethylenediamine has its nitrogen atoms at opposite ends of the molecule, its large shape allows it to reach and bind to two points of a central metal atom.

Kelvin Chung 1C

Yes, ligands are considered Lewis bases since they are electron pair donators.

Kelvin Chung 1C

Dr. Lavelle sent an email with this link:
https://lavelle.chem.ucla.edu/wp-conten ... pounds.pdf
I think we just memorize these.

Kelvin Chung 1C

You can also create a chemical equation with water for oxides. For example: (a) BaO + H 2 O --> Ba(OH) 2 The formation of hydroxide (OH - ) when BaO is added to water shows that BaO is a basic oxide. (b) SO 3 + H 2 O --> H 2 SO 4 , a strong acid For (c) and (d), we see that As 2 O 3 and Bi 2 O 3 - a...

Kelvin Chung 1C

Can LDF sometimes have more effect on the boiling point of a compound than its dipole-dipole forces? For example, when the structures of two different compounds are identical except for its central atom, are there times when the difference in the molar masses of the central atoms (and hence the diff...

Kelvin Chung 1C

Can anyone explain again what Dr. Lavelle explained about EDTA in lecture? What is its significance?

Kelvin Chung 1C

Do steric numbers change if bonds are double or triple?

Kelvin Chung 1C

Kassidy Ford 1J wrote:are we going to have to know the d hybridizations or are we only supposed to know the p hybridizations?

Since Dr. Lavelle mentioned it in class, I think we should be familiar with the d-orbital hybridizations as well.

Kelvin Chung 1C

Dr. Lavelle explained that since the Cls are pointing in opposite directions in the transplatin molecule, it's impossible for it to bind strongly (with both Cls as cisplatin is able to do) to DNA, hence making the transplatin unable to form a coordination complex with the DNA.

Kelvin Chung 1C

A molecule with 3 electron groups (3 bonds) and no lone pairs is called trigonal planar. A trigonal pyramidal molecule has 3 electron groups (3 bonds) and 1 lone pair on the central atom. A T-shaped molecule has 3 electron groups (3 bonds) and 2 lone pairs on the central atom. Basically the differen...

Kelvin Chung 1C

Also, if the atoms bonded to the central atom are not the same atoms (e.g. CH₂ClI) bond angles can differ due to differences in the different atoms' electronegativities.

Kelvin Chung 1C

Vapor pressure also differs at different temperatures. We see this because temperature is essentially a measure of the average kinetic energy of particles of whatever it is we're measuring. As this average kinetic energy rises, more particles (molecules, atoms, etc.) are able to vaporize—since some ...

Kelvin Chung 1C

The two molecules attached to the central atom are generally more electronegative than the central atom. There must be lone pairs on the molecule with a 120 degree bond angle so that the otherwise linear molecule "bends" downward through electron repulsion with these more electronegative a...

Kelvin Chung 1C

I think this figure just illustrates the electron clouds of the chlorines on the molecule. For the VSEPR section of the syllabus, Lavelle said we only need to identify the shape based on the number of bonds and lone pairs and know each shape's corresponding angle.

Kelvin Chung 1C

Dipole moments arise from differences in electronegativity, which represents a separation of charge. One part of the compound is slightly positive while the other is slightly negative. We represent this using an arrow pointing in the direction of the slightly negative portion. We can also measure th...

Kelvin Chung 1C

We can just determine which electronegativity value is higher between the two elements of a bond. The element with higher electronegativity should have a slightly negative charge and the other should be slightly positive. In some compounds, such as symmetrical ones, these dipole moments "cancel...

Kelvin Chung 1C

Formal charge just indicates the charge of each element in a molecule regardless of its charge. The formal charges of each element in the molecule should add up to the charge of the ion, or 0 if the molecule is neutral.

Kelvin Chung 1C

RoshniVarmaDis1K wrote:If formal charges that are not equal to 0 must exist, they should be as symmetrically spaced out on the outer atoms as possible. This increases surface area and makes the molecule more stable because it has lower energy.

Why does delocalization of electrons like this make the molecule more stable?

Kelvin Chung 1C

^it would probably be useful to know the charges of these ions as well!

Kelvin Chung 1C

I'm thinking that out of the three compounds listed there, Ba and Br have the highest difference in electronegativity values, followed by Ca and Br, and finally by Be and Br. That would make BaBr₂ have bonds that are primarily ionic.

Kelvin Chung 1C

In an ion, generally the formal charges should add up to the charge of the ion. In a molecule, I believe the formal charges should add up to 0.

Kelvin Chung 1C

If I understand correctly what you mean by "drawing them in a carbon line," this would give you butatriene, with a double bond between each carbon atom and the first and last carbons having two hydrogens each (H 2 C=C=C=CH 2 ). The book's arrangement of C 4 H 4 with the carbons in a "...

Kelvin Chung 1C

Dr. Lavelle gave us the length of covalent bonds in Angstroms to show us that the molecules that we draw using different resonance structures are, in actuality, have bonds that are hybrids of the single/double/triple bond.

Kelvin Chung 1C

The values that represent the electronegativity of elements are arbitrary and only used for comparison between elements.

Kelvin Chung 1C

If an atom, such as oxygen, forms a double bond and has two lone pairs of electrons, should I draw the dots for the lone pairs on diagonal sides of the O (on the other side of the double bond lines), rather than on the top and the bottom?

Kelvin Chung 1C

Nonmetals also tend to have higher electron affinities than do metals. We can see this since Groups 7, 8, and 9 generally form negative charges (additional electrons) while Groups 1 and 2 form positive charges.

Kelvin Chung 1C

andrewcj 4I wrote:
Debora Fernandez Clemente_ 4H wrote:would the bond length vary when it is a double or triple bond?

Yes! Multiple bonds will be shorter than single bonds.

For example, because a double bond is stronger than a single bond, the double bond's length will be relatively shorter since the atoms are pulled together with more strength.

Kelvin Chung 1C

Jordan Young 3E wrote:Boron also is an exception at times

Boron typically has 6 valence electrons, forming 3 covalent bonds. Right?

Kelvin Chung 1C

Dr. Lavelle showed us in class that the molecule most likely exists as a hybrid of the resonance structures by comparing the typical bond length between two atoms to the bond length between the same two atoms within a molecule. The difference in the bond lengths proves that the molecule's bonds are ...

Kelvin Chung 1C

Wouldn't the value of l in n=2 be either 0 or 1?

l=0 would correspond with the 2s subshell, which has 1 orbital.
l=1 would correspond with the 2p subshell, which has 3 orbitals.
So there would be four total orbitals in the n=2 energy level.

Kelvin Chung 1C

If you have one of the two unknown values of this equation (E or v) and need to solve for the other, use this equation.

Kelvin Chung 1C

The Balmer series refers to EM radiation that is emitted when an electron returns from a state n>2 to n=2. The Lyman series corresponds to EM radiation emitted when an electron returns from a state n>1 to n=1. The wavelengths of the EM radiation classified under the Balmer series are within the visi...

Kelvin Chung 1C

I think the answer is basically saying that for each series there is a common energy level that the electron returns to. For example, the Balmer series corresponds to the EM radiation that is emitted when an electron returns from any higher energy level to the lower energy level n=2, and Lyman to th...

Kelvin Chung 1C

In the 10/14/19 lecture, Dr. Lavelle gave an example problem: Incorrect atomic model: electron is located inside the nucleus of the atom. For the H-atom, the electron is then confined to its nuclear diameter. He explained that the nuclear diameter would be the value for the electron's indeterminacy ...

Kelvin Chung 1C

The quantum numbers all correspond to a specific orientation of an orbital, which means that they are bound to certain integers. For example, l consists of integers between 0 and n-1.

Kelvin Chung 1C

The atomic radius of Aluminum is smaller than that of Sodium. Therefore, the outer electrons of an Aluminum atom are closer to the nucleus, and thus are more strongly attracted to the nucleus than are Sodium's electrons.

Kelvin Chung 1C

Do we need to know the SI unit equivalents for each term, like the joule?

Kelvin Chung 1C

Does this mean when a question asks for number of atoms, you can substitute atoms with molecules or particles as well? Are atoms/ molecules/ chemical particles all just different names for the same item? I think the textbook usually specifies whether it is asking for the number of atoms/molecules/p...

Kelvin Chung 1C

a) l=0 describes the s-orbital, which has 1 orbital.
b) l=2 describes the d-orbital, which has 5 orbitals.
c) l=1 describes the p-orbital, which has 3 orbitals.
d) l=3 describes the f-orbital, which has 7 orbitals.

Kelvin Chung 1C

We isolate the liters of the solution since that is what the question is asking us to solve for. It's just an algebraic manipulation of the original equation to isolate the unknown variable.

Kelvin Chung 1C

Since it's asking what volume of 0.778 M should be diluted to make a FINAL SOLUTION of 150.0 mL with concentration 0.0234 M, we know that V_f = 0.1500 L and M_f = 0.0234 M. Therefore, M_i = 0.778 M, and so the question asks to find V_i, initial volume.

Kelvin Chung 1C

a) Both Copper(II) Nitrate (Cu(NO 3 ) 2 ) and Sodium Hydroxide (NaOH) are soluble in water due to the nitrate and the sodium in each substance respectively. So nitrate and sodium would be spectator ions, which are omitted from the net ionic equation. Thus, the equation would be: Cu 2+ + 2OH - ---> C...

Kelvin Chung 1C

Has anyone heard from any past CHEM 14 students whether Dr. Lavelle tests us on small details like this? Or would most of the questions on the tests/quizzes/exams be like the homework problems?

Kelvin Chung 1C

I'm pretty sure it's Avogadro's number regardless, since a mole of a substance indicates 6.022x10^23 atoms, molecules, or other chemical particles.

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