Search found 30 matches

by Nancy Hu - 4E
Mon Dec 03, 2018 3:51 pm
Forum: Naming
Topic: Roman Numeral
Replies: 5
Views: 102

Re: Roman Numeral

Is it possible to ever have a negative oxidation number? If so how would that be reflected in the name because there is no +/- sign in the brackets Yes it is possible to have a negative oxidation number. To show that it is an anion, you would add -ate at the end of the central atom's name, and its ...
by Nancy Hu - 4E
Mon Dec 03, 2018 3:38 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Negative pH?
Replies: 5
Views: 79

Re: Negative pH?

It is possible when there is a strong acid with a molar concentration greater than 1 mol/L.
by Nancy Hu - 4E
Mon Dec 03, 2018 3:30 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Tetrahedral vs. square-planar
Replies: 6
Views: 142

Re: Tetrahedral vs. square-planar

Tetrahedral uses the notation AX4 while square planar is AX4E2. This means that tetrahedral has 4 bonds to the center atom. Square planar has 4 bonds and 2 lone pair on the center atom.
by Nancy Hu - 4E
Wed Nov 28, 2018 12:14 am
Forum: Dipole Moments
Topic: Polarity of Asymmetrical Molecules
Replies: 4
Views: 89

Re: Polarity of Asymmetrical Molecules

If the structure is asymmetrical, the dipole moments won't cancel out and so the molecule would be polar.
by Nancy Hu - 4E
Tue Nov 27, 2018 11:59 pm
Forum: Hybridization
Topic: sigma and pi bonds
Replies: 5
Views: 103

Re: sigma and pi bonds

Pi bonds by themselves are actually weaker than sigma bonds because there is less area of overlap between p orbitals than s orbitals. Single bonds are weaker than double bonds because single bonds has only a sigma bond while double bonds have a sigma and pi bond.
by Nancy Hu - 4E
Tue Nov 27, 2018 11:41 pm
Forum: Hybridization
Topic: Non hybrid orbitals and pi bonds
Replies: 1
Views: 60

Re: Non hybrid orbitals and pi bonds

Yes, pi bonds only form when unhybridized p orbitals overlap.
by Nancy Hu - 4E
Sat Nov 24, 2018 7:53 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR RULE 3
Replies: 4
Views: 109

Re: VSEPR RULE 3

Single, double, and triple bonds are one area of bonding, so they all count as one region of electron density.
by Nancy Hu - 4E
Sat Nov 24, 2018 7:48 am
Forum: Hybridization
Topic: Octet Expansion and d-Orbitals
Replies: 8
Views: 163

Re: Octet Expansion and d-Orbitals

So is any element in the first 3 groups without a d-orbital in its shell unable to fulfill the octet rule? Under my current understanding, I believe any element in the first three groups don't have to meet the octet rule of maximum 8 electrons, it can exceed the octet rule since it has access to th...
by Nancy Hu - 4E
Sat Nov 24, 2018 7:35 am
Forum: Sigma & Pi Bonds
Topic: Delta Bonds
Replies: 4
Views: 114

Re: Delta Bonds

Delta bonds are formed when 4 lobes of a d orbital overlaps with 4 lobes of another d orbital.
by Nancy Hu - 4E
Sun Nov 18, 2018 10:58 am
Forum: Administrative Questions and Class Announcements
Topic: Review for Final
Replies: 2
Views: 105

Re: Review for Final

The final review sessions aren't posted on the website yet, but I would assume that they start soon. They'll probably start after Thanksgiving break.
by Nancy Hu - 4E
Sun Nov 18, 2018 10:54 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 3
Views: 109

Re: Bond Angles

Lone pairs would push the other bonding pairs further away, so the bond angles are usually less than the bond angles for the original shape.
by Nancy Hu - 4E
Sun Nov 18, 2018 10:41 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Test 3
Replies: 19
Views: 321

Re: Test 3

It would be easier to memorize them. You can also figure out the shapes by knowing how many areas of electron density there are and the lone pairs with the notation.
by Nancy Hu - 4E
Fri Nov 09, 2018 10:13 pm
Forum: Lewis Structures
Topic: Lewis Structure
Replies: 10
Views: 167

Re: Lewis Structure

Make sure that the formal charges are closest to zero. A way that makes it easier for me is to keep the valence electrons for each element in mind when drawing the lewis structure so that I don't have to guess and check the formal charges for the best structure.
by Nancy Hu - 4E
Fri Nov 09, 2018 9:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Naming the shape
Replies: 6
Views: 216

Re: Naming the shape

There is also pentagonal bipyramidal.
by Nancy Hu - 4E
Fri Nov 09, 2018 3:20 pm
Forum: Dipole Moments
Topic: Melting points
Replies: 5
Views: 87

Re: Melting points

The oxygen in H2O is electronegative and can form intermolecular hydrogen bonds. On the other hand, H2S has Van Der Waals force between the molecules instead of hydrogen bonds. The h-bonds between the hydrogen and oxygen of water molecules are stronger than the Van Der Walls force so the melting poi...
by Nancy Hu - 4E
Fri Nov 02, 2018 11:16 pm
Forum: Trends in The Periodic Table
Topic: Ionic Radius
Replies: 2
Views: 56

Re: Ionic Radius

The order of increasing ionic radius is Cl^1-,S^2-,P^3- because even though they have the same electron configuration, the smaller ions are the ones with the larger atomic number because they have the most positive charge in the nucleus because of the number of protons and so they have the largest p...
by Nancy Hu - 4E
Fri Nov 02, 2018 10:45 pm
Forum: Trends in The Periodic Table
Topic: Difference between Atomic Radius and Ionic Radius
Replies: 2
Views: 202

Re: Difference between Atomic Radius and Ionic Radius

Atomic radius and ionic radius are both the measure of the center of the nucleus and the outermost shell. In a neutral atom, both the atomic and ionic radius would be the same. The ionic radius is bigger in a anion and smaller in a cation compared to their parent atom.
by Nancy Hu - 4E
Fri Nov 02, 2018 10:33 pm
Forum: Lewis Structures
Topic: Midterm Chemical Formula Names
Replies: 3
Views: 70

Re: Midterm Chemical Formula Names

A TA told me that they will give the compounds but we should still know the basic ones like NaOH.
by Nancy Hu - 4E
Sat Oct 27, 2018 10:03 am
Forum: Trends in The Periodic Table
Topic: Trends in the periodic table & electron configuration
Replies: 5
Views: 93

Re: Trends in the periodic table & electron configuration

Trends and electron configuration are related in that you can see the reasoning behind the trends when writing out the electron configurations of elements. For example, a full valence shell is the most stable electron configuration.
by Nancy Hu - 4E
Sat Oct 27, 2018 9:49 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 7
Views: 268

Re: Midterm

Our TA's might go over what is on the midterm during discussions. It also might be helpful to look at the practice problems that review session have.
by Nancy Hu - 4E
Sat Oct 27, 2018 9:19 am
Forum: Lewis Structures
Topic: Exceptions to octet rule
Replies: 1
Views: 58

Exceptions to octet rule

Can someone help explain why H, He, Li, and Be are exceptions to the octet rule?
by Nancy Hu - 4E
Sat Oct 20, 2018 11:06 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 4th quantum number question [ENDORSED]
Replies: 3
Views: 89

Re: 4th quantum number question [ENDORSED]

So the 4th quantum number describes the spin of an electron. If the electron is spinning up, it has a value of +1/2. If the electron is spinning down, it has a value of -1/2. It is just used to describe the orientation of an electron in an orbital.
by Nancy Hu - 4E
Sat Oct 20, 2018 10:51 am
Forum: *Shrodinger Equation
Topic: Test 2 and Shrodinger Equation
Replies: 3
Views: 188

Re: Test 2 and Shrodinger Equation

During discussion, my TA said that we don't need to know how to do calculations using the Schrodinger equation for the test. We just need to know the concepts behind the equation.
by Nancy Hu - 4E
Fri Oct 19, 2018 12:27 pm
Forum: Student Social/Study Group
Topic: Next week's quiz
Replies: 5
Views: 169

Re: Next week's quiz

Electron configuration plays a part in quantum numbers so it would probably be better to know the electron configurations for the test. Even if it isn't on the test, it wouldn't hurt to look over it a little.
by Nancy Hu - 4E
Sat Oct 13, 2018 11:59 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect
Replies: 2
Views: 60

Re: Photoelectric Effect

The excess energy is used to eject electrons so it is converted into kinetic energy. Kinetic energy can be solved by using the formula 1/2mv^2.
by Nancy Hu - 4E
Thu Oct 11, 2018 2:48 pm
Forum: Properties of Light
Topic: Photon energy
Replies: 3
Views: 67

Re: Photon energy

When the photon is greater than or equal to the threshold energy, electrons can be ejected.
by Nancy Hu - 4E
Thu Oct 11, 2018 2:43 pm
Forum: Administrative Questions and Class Announcements
Topic: Homework and discussion grading?
Replies: 2
Views: 82

Re: Homework and discussion grading?

I don't know when the grades for the discussion or homework will be posted, but my TA passed back the homework assignment from week one in my discussion this week.
by Nancy Hu - 4E
Fri Oct 05, 2018 10:03 am
Forum: Significant Figures
Topic: Scientific Notation
Replies: 7
Views: 118

Re: Scientific Notation

It's really just personal preference. If you find it a lot easier to write out numbers especially long ones in scientific notation, you can. It's also a lot easier to use scientific notaion when you want to keep numbers at a certain sig fig.
by Nancy Hu - 4E
Fri Oct 05, 2018 10:00 am
Forum: Empirical & Molecular Formulas
Topic: Empirical formula set up
Replies: 9
Views: 172

Re: Empirical formula set up

It is just a lot easier to do calculations if you change the percentage based on 100g. You don't have to do any complicated calculations.
by Nancy Hu - 4E
Fri Oct 05, 2018 9:53 am
Forum: Significant Figures
Topic: Zeros in sig figs
Replies: 4
Views: 99

Re: Zeros in sig figs

Hi! So you count zeros when there's a decimal point after for example in 280. there are 3 sig figs. If you have a number like 0.0005 where the zeros are after the decimal point you only have one sig fig. if you have a number with zeros in the middle you would count them for example 34.008 that is 5 ...

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