Search found 30 matches

by Kelvin Chung 1C
Tue Nov 05, 2019 6:25 pm
Forum: Dipole Moments
Topic: Dipole Moments
Replies: 5
Views: 47

Re: Dipole Moments

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...
by Kelvin Chung 1C
Tue Nov 05, 2019 6:21 pm
Forum: Dipole Moments
Topic: Dipole moments
Replies: 1
Views: 24

Re: Dipole moments

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...
by Kelvin Chung 1C
Tue Nov 05, 2019 5:37 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge when it's not labelled?
Replies: 2
Views: 31

Re: Formal Charge when it's not labelled?

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.
by Kelvin Chung 1C
Tue Nov 05, 2019 11:19 am
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge/Lewis structures
Replies: 5
Views: 26

Re: Formal Charge/Lewis structures

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?
by Kelvin Chung 1C
Tue Nov 05, 2019 11:06 am
Forum: Ionic & Covalent Bonds
Topic: Polyatomic Ions
Replies: 2
Views: 28

Re: Polyatomic Ions

^it would probably be useful to know the charges of these ions as well!
by Kelvin Chung 1C
Thu Oct 31, 2019 8:42 pm
Forum: Electronegativity
Topic: 2D.3
Replies: 2
Views: 28

Re: 2D.3

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.
by Kelvin Chung 1C
Thu Oct 31, 2019 8:34 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charges on Atoms Summed in Ions?
Replies: 6
Views: 22

Re: Formal Charges on Atoms Summed in Ions?

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.
by Kelvin Chung 1C
Thu Oct 31, 2019 8:32 pm
Forum: Resonance Structures
Topic: C4H4
Replies: 2
Views: 17

Re: C4H4

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 "...
by Kelvin Chung 1C
Thu Oct 31, 2019 8:22 pm
Forum: Lewis Structures
Topic: Angstrom Measurements on Lewis Structures
Replies: 3
Views: 17

Re: Angstrom Measurements on Lewis Structures

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.
by Kelvin Chung 1C
Thu Oct 31, 2019 8:19 pm
Forum: Ionic & Covalent Bonds
Topic: Electronegativity
Replies: 7
Views: 29

Re: Electronegativity

The values that represent the electronegativity of elements are arbitrary and only used for comparison between elements.
by Kelvin Chung 1C
Fri Oct 25, 2019 5:52 am
Forum: Lewis Structures
Topic: Where to start putting dots for electrons
Replies: 10
Views: 59

Re: Where to start putting dots for electrons

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?
by Kelvin Chung 1C
Fri Oct 25, 2019 5:50 am
Forum: Ionic & Covalent Bonds
Topic: Properties of Metals/Nonmetals/Metalloids
Replies: 3
Views: 16

Re: Properties of Metals/Nonmetals/Metalloids

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.
by Kelvin Chung 1C
Fri Oct 25, 2019 5:39 am
Forum: Bond Lengths & Energies
Topic: Bond lengths
Replies: 15
Views: 103

Re: Bond lengths

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.
by Kelvin Chung 1C
Fri Oct 25, 2019 5:35 am
Forum: Octet Exceptions
Topic: Octet exception examples
Replies: 9
Views: 74

Re: Octet exception examples

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

Boron typically has 6 valence electrons, forming 3 covalent bonds. Right?
by Kelvin Chung 1C
Fri Oct 25, 2019 5:31 am
Forum: Resonance Structures
Topic: Resonance Structures
Replies: 4
Views: 39

Re: Resonance Structures

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 ...
by Kelvin Chung 1C
Wed Oct 16, 2019 1:05 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: HW Help
Replies: 3
Views: 21

Re: HW Help

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.
by Kelvin Chung 1C
Wed Oct 16, 2019 12:54 am
Forum: Einstein Equation
Topic: Equation use
Replies: 6
Views: 35

Re: Equation use

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.
by Kelvin Chung 1C
Wed Oct 16, 2019 12:33 am
Forum: Properties of Light
Topic: Balmer and Lyman in real world
Replies: 1
Views: 12

Re: Balmer and Lyman in real world

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...
by Kelvin Chung 1C
Wed Oct 16, 2019 12:20 am
Forum: Properties of Light
Topic: 1A.11
Replies: 2
Views: 16

Re: 1A.11

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...
by Kelvin Chung 1C
Tue Oct 15, 2019 11:32 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Indeterminacy in Position [ENDORSED]
Replies: 5
Views: 35

Indeterminacy in Position [ENDORSED]

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 ...
by Kelvin Chung 1C
Fri Oct 11, 2019 9:48 am
Forum: Quantum Numbers and The H-Atom
Topic: Quantum number as a discrete unit
Replies: 3
Views: 48

Re: Quantum number as a discrete unit

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.
by Kelvin Chung 1C
Fri Oct 11, 2019 9:40 am
Forum: Trends in The Periodic Table
Topic: Ionization Energy: Na vs. Al
Replies: 3
Views: 29

Re: Ionization Energy: Na vs. Al

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.
by Kelvin Chung 1C
Fri Oct 11, 2019 9:26 am
Forum: Einstein Equation
Topic: Units
Replies: 17
Views: 551

Re: Units

Do we need to know the SI unit equivalents for each term, like the joule?
by Kelvin Chung 1C
Fri Oct 11, 2019 9:14 am
Forum: SI Units, Unit Conversions
Topic: Help on Fundamentals: E21
Replies: 7
Views: 71

Re: Help on Fundamentals: E21

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...
by Kelvin Chung 1C
Fri Oct 11, 2019 9:10 am
Forum: Properties of Light
Topic: Homework question 1D11?
Replies: 1
Views: 31

Re: Homework question 1D11?

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.
by Kelvin Chung 1C
Thu Oct 03, 2019 11:48 pm
Forum: Molarity, Solutions, Dilutions
Topic: HW question G11
Replies: 3
Views: 23

Re: HW question G11

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.
by Kelvin Chung 1C
Thu Oct 03, 2019 11:41 pm
Forum: Molarity, Solutions, Dilutions
Topic: HW question G15a
Replies: 1
Views: 18

Re: HW question G15a

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 Vf = 0.1500 L and Mf = 0.0234 M. Therefore, Mi = 0.778 M, and so the question asks to find Vi, initial volume.
by Kelvin Chung 1C
Thu Oct 03, 2019 11:31 pm
Forum: Limiting Reactant Calculations
Topic: textbook problem help
Replies: 2
Views: 42

Re: textbook problem help

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...
by Kelvin Chung 1C
Thu Oct 03, 2019 11:12 pm
Forum: SI Units, Unit Conversions
Topic: Can someone explain why we use kg for mass as the base unit?
Replies: 9
Views: 298

Re: Can someone explain why we use kg for mass as the base unit?

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?
by Kelvin Chung 1C
Thu Oct 03, 2019 10:58 pm
Forum: SI Units, Unit Conversions
Topic: Help on Fundamentals: E21
Replies: 7
Views: 71

Re: Help on Fundamentals: E21

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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