Search found 35 matches

by Lauren Stack 4B
Sun Nov 17, 2019 12:28 am
Forum: Electronegativity
Topic: Symbols for partial charge
Replies: 3
Views: 10

Re: Symbols for partial charge

The various delta symbols do in fact show a partial charge. If you think about a water molecule, the two hydrogens will have a delta positive and the oxygen will have a delta negative. The arrows point towards the negative atom. So the point of the arrow will go towards the oxygen in the case of wat...
by Lauren Stack 4B
Sun Nov 17, 2019 12:01 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 5
Views: 21

Re: Bond Angles

For each of the different molecular geometry shapes (VSEPR), I am memorizing the possible angles. Otherwise, I believe that is important to understand why an angle might be slightly less than expected (such as 107deg instead of expected 109.5deg) by understanding the role that lone pairs play in rep...
by Lauren Stack 4B
Sat Nov 16, 2019 11:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Electronegativity
Replies: 5
Views: 15

Re: Electronegativity

I do not believe we need to know exact values for electronegativity. I think that knowing the general periodic trends associated with it are sufficient in that noble gases are not electronegative and electronegativity increases up a column and across a row. Comparing relative electronegativity can b...
by Lauren Stack 4B
Sat Nov 16, 2019 11:42 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Calculating formal charge
Replies: 3
Views: 10

Re: Calculating formal charge

When calculating formal charge, the order that you do it in should not matter. Formal charge is assigned individually to each atom in a molecule by taking the number of valence electrons and subtracting the sum of the number of bonds and the number of lone electrons. Overall, you want the most elect...
by Lauren Stack 4B
Sat Nov 16, 2019 11:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 4
Views: 18

Re: Bond Angles

What I noted is that you should be able to tell when the bond angles are less than the expected (i.e. less than 109.5 deg in the example you give), but it is also helpful to be able to rank them when comparing various shapes, such as the bond angles on a molecule with one lone pair against a molecul...
by Lauren Stack 4B
Sun Nov 10, 2019 3:13 pm
Forum: Bond Lengths & Energies
Topic: Bond Strength
Replies: 4
Views: 8

Re: Bond Strength

I believe that exact values of bond strength are determined experimentally through finding the dissociation energy. For our purposes, we can use a provided table of bond strengths and lengths to determine strength. The more bonds there are between atoms, the stronger the bond. Additionally, the shor...
by Lauren Stack 4B
Sun Nov 10, 2019 3:07 pm
Forum: Coordinate Covalent Bonds
Topic: Coordinate Covalent Bond
Replies: 6
Views: 20

Re: Coordinate Covalent Bond

A coordinate covalent bond is special because both electrons in the shared lone pair came from the same atom. In a regular covalent bond, each atom in the bond provide an electron. I believe that the strength of a coordinate covalent bond is equivalent to any other covalent bond and its importance i...
by Lauren Stack 4B
Sun Nov 10, 2019 2:58 pm
Forum: Lewis Structures
Topic: Lewis acids and bases?
Replies: 7
Views: 24

Re: Lewis acids and bases?

I would think that we are held responsible for understanding Lewis acids and bases for all of the upcoming assessments. It appears on the syllabus in Focus 3: Chemical bonds. We did not complete all of focus 3 before the midterm, but I assume that the material will be fair game on future tests. I re...
by Lauren Stack 4B
Sun Nov 10, 2019 2:51 pm
Forum: Ionic & Covalent Bonds
Topic: C, N, O, and F
Replies: 13
Views: 77

Re: C, N, O, and F

As Carbon, Nitrogen, Oxygen, and Fluorine are all located in period 2 of the periodic table, their valence electrons are found in n=2. Thus, they do not have the extra 3d subshell that would allow them to have an expanded octet an must follow the octet guideline. Furthermore, although we try to mini...
by Lauren Stack 4B
Sun Nov 10, 2019 2:47 pm
Forum: Ionic & Covalent Bonds
Topic: covalent relationship to polarizability
Replies: 4
Views: 23

Re: covalent relationship to polarizability

When atoms are highly polarizable or have high polarizing power, they are able to pull the electrons between them closer to the cation. An ionic bond is formed by the attraction between two oppositely charged atoms. As a covalent bond is defined by a sharing of electrons between the two bonded atoms...
by Lauren Stack 4B
Sat Nov 02, 2019 11:31 pm
Forum: Electronegativity
Topic: What is isoelectronic?
Replies: 13
Views: 49

Re: What is isoelectronic?

Isoelectronic simply means that the atoms being compared have the same number of electrons. This is often demonstrated by ions, like S- being isoelectronic with Cl.
by Lauren Stack 4B
Sat Nov 02, 2019 11:24 pm
Forum: Octet Exceptions
Topic: Covalent Bond
Replies: 4
Views: 16

Re: Covalent Bond

Coordinate covalent bonds appear as normal covalent bonds with two electrons shared between two atoms. What makes coordinate bonds special is that the two electrons that are shared both came from one atom, rather than each atom contributing one electron.
by Lauren Stack 4B
Sat Nov 02, 2019 11:19 pm
Forum: Lewis Structures
Topic: Expanded Octet
Replies: 3
Views: 22

Re: Expanded Octet

Atoms with an open d or f orbital can have an expanded octet. Thus, atoms in the n=3 level or greater can have this occur. As for determining if an atom as an expanded octet, it is important to assess its formal charge and adjust the structure accordingly to get the formal charge of all atoms as clo...
by Lauren Stack 4B
Sat Nov 02, 2019 11:11 pm
Forum: Lewis Structures
Topic: Dino Nugs 12b
Replies: 5
Views: 31

Re: Dino Nugs 12b

You want the most electronegative atom to take the negative formal charge. In this case, it is Oxygen and you would want the -1 formal charge to be assigned to it.
by Lauren Stack 4B
Sat Nov 02, 2019 11:04 pm
Forum: Ionic & Covalent Bonds
Topic: ionic vs. covalent
Replies: 7
Views: 34

Re: ionic vs. covalent

Solely based off of the visual representation of a Lewis Structure, a covalent bond is represented with a line between two atoms, as they are sharing electrons. In an ionic bond, the atoms are not sharing electrons and are not represented with a line between them.
by Lauren Stack 4B
Sun Oct 27, 2019 8:04 pm
Forum: Trends in The Periodic Table
Topic: Ionization energy
Replies: 12
Views: 59

Re: Ionization energy

I believe that it is most important to understand the general trends associated with ionization energy. Ionization energy is said to be the energy needed to remove an electron from an atom in the gas phase. Thus, ionization energy decreases down a group and increases across a period.
by Lauren Stack 4B
Sun Oct 27, 2019 8:01 pm
Forum: Trends in The Periodic Table
Topic: Central Atom
Replies: 13
Views: 35

Re: Central Atom

Typically the atom with the lowest electronegativity is the central atom. The only exception to the rule is Hydrogen.
by Lauren Stack 4B
Sun Oct 27, 2019 7:57 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron configurations
Replies: 3
Views: 20

Re: Electron configurations

The only time to expand into the descriptive x, y, and z is when it is specified in the question or asked for. Otherwise, I believe it is fine to leave the configuration in its simplified form (no x, y, z). The x, y, and z are not necessarily part of the 4 main quantum numbers.
by Lauren Stack 4B
Sun Oct 27, 2019 7:54 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: p-orbitals
Replies: 11
Views: 25

Re: p-orbitals

I believe that you can leave it as the more simplified version. If you look in the periodic table in the textbook, they list electron configurations for various elements and all of them are left in the simplified form (not displaying the x,y,z)
by Lauren Stack 4B
Sun Oct 27, 2019 7:51 pm
Forum: Ionic & Covalent Bonds
Topic: Resonance
Replies: 10
Views: 52

Re: Resonance

Having resonance does not necessarily mean that there are exactly three ways to draw the Lewis structure. Rather, resonance means that the molecule being examined has more a more complex bonding structure. A Lewis structure is a simplification of what a molecule really is, as demonstrated by the dif...
by Lauren Stack 4B
Sun Oct 20, 2019 11:28 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Multi-electron atoms
Replies: 7
Views: 17

Re: Multi-electron atoms

Hydrogen is the only element that has one electron in its ground state. Otherwise, all other elements can be considered multi-electron atoms. Helium could hypothetically be stripped of an electron (even though highly unlikely/extremely difficult because it is highly stable) and become a single-elect...
by Lauren Stack 4B
Sun Oct 20, 2019 11:20 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg
Replies: 5
Views: 26

Re: Heisenberg

To address Quresh’s question: Momentum is found by multiplying mass times velocity (p=mv). It describes the amount of resistance to stopping that an object in motion has. If you think about two balls rolling at the same velocity but with different weights, the heavier one has more momentum and is th...
by Lauren Stack 4B
Sun Oct 20, 2019 11:12 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Exceptions to Orbital Rules
Replies: 8
Views: 55

Re: Exceptions to Orbital Rules

The exceptions to the expected electron configurations come with Chromium and Copper. Chromium’s electron configuration is [Ar] 3d^5 4s^1. Copper’s is [Ar] 3d^10 4s^1. As for what half filled and full subshells mean, a d subshell can have up to 10 electrons in it, and half-full would be 5 electrons ...
by Lauren Stack 4B
Sun Oct 20, 2019 11:06 pm
Forum: Properties of Electrons
Topic: What's the difference between a shell, a subshell, an energy level, and an orbital?
Replies: 8
Views: 45

Re: What's the difference between a shell, a subshell, an energy level, and an orbital?

A shell is defined by n, which can be whole number values (1, 2, 3, etc). The term subshell refers to the l (s, p, d, f) and the shapes that are made by the expected/potential location of the electron. An orbital is a combination/description of all of the quantum numbers (which are n, l, ml, and ms)...
by Lauren Stack 4B
Sun Oct 20, 2019 10:52 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: What is electron configuration?
Replies: 3
Views: 24

Re: What is electron configuration?

An electron configuration is the symbolic representation of where an electron is located within an atom. Each of the levels within electron configuration denotes a certain amount of energy that an electron possesses. An element can be defined by its electron configuration because its is marked by it...
by Lauren Stack 4B
Sun Oct 13, 2019 10:15 pm
Forum: Properties of Light
Topic: De Broglie equation
Replies: 4
Views: 28

Re: De Broglie equation

De Broglie's equation is used to find the wavelength.
The equation itself is:
Wavelength = Planck's constant / (mass X velocity)
The units of planck's constant (m^2kg/s) cancel down to meters, as it is divided by mass (kg) and velocity (m/s) respectively.
by Lauren Stack 4B
Sun Oct 13, 2019 10:04 pm
Forum: DeBroglie Equation
Topic: Detectable wavelike properties
Replies: 1
Views: 11

Re: Detectable wavelike properties

In lecture, Dr. Lavelle said that a particle with less than 10^-15m does not have detectable wavelike properties. So anything larger than that should qualify.
by Lauren Stack 4B
Sun Oct 13, 2019 9:48 pm
Forum: Properties of Light
Topic: Reading entire chapters before class?
Replies: 4
Views: 35

Re: Reading entire chapters before class?

I tend to do most of the reading listed on the syllabus above the problem set before I attempt to do any problems. I only read what he has listed online. For example, he omitted section 1C for the Quantum World. I don't take notes on everything, only main formulas or things that are essential or thi...
by Lauren Stack 4B
Sun Oct 13, 2019 9:31 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect
Replies: 3
Views: 28

Re: Photoelectric Effect

Light has both wave-like and particle-like tendencies. The particle-like behavior is reflected in photons, which I think of as a small package of energy.
by Lauren Stack 4B
Sun Oct 13, 2019 9:27 pm
Forum: Properties of Electrons
Topic: Decrease in Quantum level
Replies: 3
Views: 13

Re: Decrease in Quantum level

If you think of the concept that energy is neither created or destroyed, the release of the light reflects a decrease in energy for the atom as a whole. The further the gap between the starting and final energy levels does impact the frequency of the light emitted, thus allowing us to analyze the va...
by Lauren Stack 4B
Fri Oct 04, 2019 10:35 pm
Forum: Balancing Chemical Reactions
Topic: Understanding how to get whole #s [ENDORSED]
Replies: 18
Views: 130

Re: Understanding how to get whole #s [ENDORSED]

If you are simply converting from grams to moles, or vice versa, having decimals is acceptable, as long as they go along with the rules of significant figures. In the case of 2.44, you have three significant figures listed. If you are making an empirical formula, you should not have decimals for the...
by Lauren Stack 4B
Fri Oct 04, 2019 10:26 pm
Forum: Molarity, Solutions, Dilutions
Topic: Clarification
Replies: 7
Views: 78

Re: Clarification

The moles of solute remain the same, regardless of the dilution. There is a set number of molecules of the solute in a solution. Even if more solvent is added, the number of molecules of solute will not change, as there is no solute being added or removed. There is simply more solvent being added, w...
by Lauren Stack 4B
Fri Oct 04, 2019 10:20 pm
Forum: Properties of Light
Topic: Amplitude
Replies: 6
Views: 44

Re: Amplitude

Wavelength and frequency are inversely related, as when they are multiplied, they result in a constant. I believe that amplitude is a separate value with no relation to the other two. For example, a wave might have a set frequency, and thus a set wavelength to compensate. The amplitude could be any ...
by Lauren Stack 4B
Fri Oct 04, 2019 10:07 pm
Forum: Empirical & Molecular Formulas
Topic: Difference between empirical and molecular formulas
Replies: 6
Views: 51

Re: Difference between empirical and molecular formulas

The empirical formula shows only the ratio/proportions of atoms of the elements present in a molecule. Conversely, the molecular formula shows the exact number of atoms of each element that are present in a molecule. The way that I remember the difference is the when you want to look at a specific m...
by Lauren Stack 4B
Fri Oct 04, 2019 9:56 pm
Forum: Student Social/Study Group
Topic: Final Jitters
Replies: 61
Views: 18469

Re: Final Jitters

As many of us do, I also struggle with stress/jitters before a large exam. Some of the strategies to cope with it that I have found useful are: 1. Take a break from the material and do something active. I personally like going to the gym or running. It helps me get my mind off of the problems at han...

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