CHEMISTRY COMMUNITY

Quynh Vo

You can identify the ionic charge by looking at the periodic table. It depends on how many valence electrons it has and whether it would lose electrons or gain them.

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what is an oxidation state? how do we know what it is in a certain compound?

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There is a central ion/atom and the ligands attached to it.

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cis have the same bonds on one side and trans have the same bonds on opposite sides. Cis would be polar since the bonds don't cancel out and trans would be non-polar.

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I think we should draw out the lewis structure to figure out what it is.

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Anything inside the brackets are a part of the coordination sphere.

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How do we know what the coordination number is and why is it important?

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cisplatin is more efficient to bonding to cells because of its structure

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cis means the atoms are on the same side while trans means they're on opposite sides from each other. The determines if they are polar or non polar

Quynh Vo

single bond = 1 sigma
double bond = 1 sigma, 1 pi
triple bond = 1 sigma, 2 pi

Quynh Vo

A sigma bond is a direct overlap between two orbitals.

Quynh Vo

The shape of the molecule does affect it through surface area. The larger the surface area, the more opportunity for Van der Waals interactions which affects other things such as boiling/melting points.

Quynh Vo

On one plane (the trigonal one), the angles are 120 degrees from each other. The angle of the atom on that plane and the one sticking out above is 90 degrees. The angle of the one above and the one below is 180 degrees.

Quynh Vo

It depends on the shape of the molecule which can a useful method to remember angles. For example, if it's linear, they're 180 degrees from another. Trigonal planar models are usually 120 degrees from each other and tetrahedral are 109.5 degrees from each other.

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Having the electrons the farthest apart means they are stable because they are equally repelling from the other elements, thus allowing little movement/instability.

Quynh Vo

The angles would be the same distance apart if they're the same element. But if there is at least one bonded to a different element, it will be different.

Quynh Vo

Trigonal planar molecules have three bonded densities whereas tetrahedral shaped have four. For trigonal, the bonds are 120 degrees apart and for tetrahedral, they're 109.5 degrees apart.

Quynh Vo

How does the atomic radius of an atom correlate to its boiling point/melting point?

Quynh Vo

Ion-ion bonds have the highest boiling points whereas london force have the lowest boiling points.

Quynh Vo

Van der Waals bonds are the weakest of the IMF as it depends on the position of the electron. It's weak because the electron are constantly moving, creating temporary dipoles.

Quynh Vo

You usually always fill 4s before 3d (with exceptions of Cr and Cu) but I guess after both orbitals are filled, it wouldn't matter when writing it out?

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4s is originally lower energy than 3d, but once 3d is filled, it becomes higher energy than 3d. Therefore the electron will be removed from 4s before 3d because electrons are removed from the higher energy orbital.

Quynh Vo

The work function/threshold energy is relevant in photoelectric effect problems. The energy of the photon minus the threshold energy equals the kinetic energy.

Quynh Vo

What is the unit for wavelength in the de broglie equation? Is it meters or nanometers or other?

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If the electron and proton have the same wavelength, the electron will have the faster velocity because of the lighter mass. You can prove this by plugging the constants into the equation and comparing the speed.

Quynh Vo

Drawing it all out can help you keep track of the electrons. It's important to draw them when there are lone pairs too.

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You calculate the number of electrons (plus/subtract positive/negative charge) and then draw the lewis structure. You also put brackets around the entire model and indicate the charge on the top right outside the brackets.

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Fluorine's atomic size is smaller than Chlorine.

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No, it does not apply to Boron. It only has six electrons.

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Cation are atoms with positive charge whereas anion are negatively charged atoms. This is important when we are drawing them and determining which structure is more stable.

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Quynh Vo

The answer would be .2 because that's the value that is uncertain. It is the difference of the possible positions.

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You can use the the De Broglie equation when you want to calculate the wavelength of a particle when it is traveling at a certain velocity.

Quynh Vo

You can use the Rydberg's formula to when you want to calculate the wavelength of radiation when it transitions from different shell levels.

Quynh Vo

Rydberg's constant is not a negative number.

Megan_1F wrote:Is Rydberg's constant negative? Or is the equation itself just negative?

Quynh Vo

What is the difference between higher intensity light and a shorter wavelength?

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Electrons have wave-like properties because like a wave, when electron passes through a crystal, there are diffractions.

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Yes, threshold energy is totally different depending on which element it is.

Quynh Vo

In regards to light, intensity is the amount of energy per m/s. Frequency is the amount of cycles a wave length occurs within an amount of time.

Quynh Vo

After getting the empirical formula as C4H5N2O, we have to find the molecular formula but they never gave us the molar mass spectrometry. How would we calculate that ourselves?

Quynh Vo

The theoretical yield is the best possible outcome which means it would have to use the entire limiting reagent.

Quynh Vo

I’m pretty sure we have to fully show out how you got those calculations through math/work but after that, a word explanation like that should be fine.

Quynh Vo

At the end, you should’ve multiplied the 5.03 mol AlCl3 with the molar mass which is about 133.331. You have to divide the 300 g by the answer you got to get the percent yield.

Quynh Vo

For this, you would need to multiply it by 2 to get a whole number. Rounding 2.5 either up and down is too much for the formula to have the same composition.

Quynh Vo

How come some numbers have a .0 at the end in questions? For example, it is 30.0 g instead of just 30 g.

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