### Equations We’ve Learned So Far

Posted:

**Sat Oct 12, 2019 7:49 pm**I’m having some trouble with all the equations that we’ve learned so far. Can someone list them and explain when we’re supposed to use each one?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=14&t=47105

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Posted: **Sat Oct 12, 2019 7:49 pm**

I’m having some trouble with all the equations that we’ve learned so far. Can someone list them and explain when we’re supposed to use each one?

Posted: **Sat Oct 12, 2019 7:54 pm**

Is there a specific example or equation you're having trouble with? I'm not sure if I can describe all of them.

Posted: **Sat Oct 12, 2019 8:13 pm**

Ryan Chew 1C wrote:Is there a specific example or equation you're having trouble with? I'm not sure if I can describe all of them.

Maybe for problem 1a.15 I’m confused about the Rydberg equation.

Posted: **Sat Oct 12, 2019 8:14 pm**

Hi Ellis! This is Ariel.

Here's a general list from my notes:

c = λ ν

-- Used to calculate wavelength/frequency

E(photon) = h ν

-- Used to calculate energy per single photon

-- Bohr Frequency Condition: v = ∆E/h; used to calculate frequency

E(photon) = Work Function/Threshold Energy + EK

EK =(1/2)mv^2

-- Used for Photoelectric Effect problems (when an electron is ejected)

En = -(h)(R)/n^2 for n =1,2...

-- Used for electron transitions for the H-atom spectrum

λ = h/p, where p = mass x velocity; λ = h/(mass x velocity)

-- De Broglie Equation: Used to find wavelength/"wavelike properties" of moving objects (only noticeable for objects with extremely small mass)

There is also the Heisenberg Indeterminacy Equation (∆p ∆x ≥ h/4π) and Schrodinger's Equation (Hψ = Eψ), but we haven't covered those yet! Hope this helps! Also, there is a list of constants and equations on the Chem 14A page, and it has helped me keep track of all of these! Let me know if there is a mistake here or if there is an easier way to list these!

Here's a general list from my notes:

c = λ ν

-- Used to calculate wavelength/frequency

E(photon) = h ν

-- Used to calculate energy per single photon

-- Bohr Frequency Condition: v = ∆E/h; used to calculate frequency

E(photon) = Work Function/Threshold Energy + EK

EK =(1/2)mv^2

-- Used for Photoelectric Effect problems (when an electron is ejected)

En = -(h)(R)/n^2 for n =1,2...

-- Used for electron transitions for the H-atom spectrum

λ = h/p, where p = mass x velocity; λ = h/(mass x velocity)

-- De Broglie Equation: Used to find wavelength/"wavelike properties" of moving objects (only noticeable for objects with extremely small mass)

There is also the Heisenberg Indeterminacy Equation (∆p ∆x ≥ h/4π) and Schrodinger's Equation (Hψ = Eψ), but we haven't covered those yet! Hope this helps! Also, there is a list of constants and equations on the Chem 14A page, and it has helped me keep track of all of these! Let me know if there is a mistake here or if there is an easier way to list these!

Posted: **Sat Oct 12, 2019 8:17 pm**

Ariel Fern 3A wrote:Hi Ellis! This is Ariel.

Here's a general list from my notes:

c = λ ν

-- Used to calculate wavelength/frequency

E(photon) = h ν

-- Used to calculate energy per single photon

-- Bohr Frequency Condition: v = ∆E/h; used to calculate frequency

E(photon) = Work Function/Threshold Energy + EK

EK =(1/2)mv^2

-- Used for Photoelectric Effect problems (when an electron is ejected)

En = -(h)(R)/n^2 for n =1,2...

-- Used for electron transitions for the H-atom spectrum

λ = h/p, where p = mass x velocity; λ = h/(mass x velocity)

-- De Broglie Equation: Used to find wavelength/"wavelike properties" of moving objects (only noticeable for objects with extremely small mass)

There is also the Heisenberg Indeterminacy Equation (∆p ∆x ≥ h/4π) and Schrodinger's Equation (Hψ = Eψ), but we haven't covered those yet! Hope this helps! Also, there is a list of constants and equations on the Chem 14A page, and it has helped me keep track of all of these! Let me know if there is a mistake here or if there is an easier way to list these!

Haha thanks Ariel! I really appreciate it this is super helpful :)

Posted: **Sat Oct 12, 2019 8:25 pm**

It's important to distinguish between equations that are relevant to light (EM radiation) and quantum movement of electrons. For light specifically, you should pay attention to:

These two equations are applied to light in the theory that light is a wave:

c = λv = 3*10^8 (speed of light = wavelength * frequency)

E=hv (Energy = Planck's constant * frequency)

h = 6.63 * 10^-34 (Planck's constant)

These two equations are applied to light in the theory that light is a particle (photon):

E (energy of photon) - Work Function (energy to remove electron from a metal) = Kinetic Energy

When a photon hits a metal surface, it can remove electrons from that metal. The energy of the photon moves to the electron, causing the electron to move.

E = (-hR)/n^2

n = energy level

R = Rydberg Constant = 3.29 * 10^15

Remember, De Brogile Equation is for electrons only. Do not use this equation with light!

These two equations are applied to light in the theory that light is a wave:

c = λv = 3*10^8 (speed of light = wavelength * frequency)

E=hv (Energy = Planck's constant * frequency)

h = 6.63 * 10^-34 (Planck's constant)

These two equations are applied to light in the theory that light is a particle (photon):

E (energy of photon) - Work Function (energy to remove electron from a metal) = Kinetic Energy

When a photon hits a metal surface, it can remove electrons from that metal. The energy of the photon moves to the electron, causing the electron to move.

E = (-hR)/n^2

n = energy level

R = Rydberg Constant = 3.29 * 10^15

Remember, De Brogile Equation is for electrons only. Do not use this equation with light!

Posted: **Sat Oct 12, 2019 8:26 pm**

It's important to distinguish between equations that are relevant to light (EM radiation) and quantum movement of electrons. For light specifically, you should pay attention to:

These two equations are applied to light in the theory that light is a wave:

c = λv = 3*10^8 (speed of light = wavelength * frequency)

E=hv (Energy = Planck's constant * frequency)

h = 6.63 * 10^-34 (Planck's constant)

These two equations are applied to light in the theory that light is a particle (photon):

E (energy of photon) - Work Function (energy to remove electron from a metal) = Kinetic Energy

When a photon hits a metal surface, it can remove electrons from that metal. The energy of the photon moves to the electron, causing the electron to move.

E = (-hR)/n^2

n = energy level

R = Rydberg Constant = 3.29 * 10^15

Remember, De Brogile Equation is for electrons only. Do not use this equation with light!

These two equations are applied to light in the theory that light is a wave:

c = λv = 3*10^8 (speed of light = wavelength * frequency)

E=hv (Energy = Planck's constant * frequency)

h = 6.63 * 10^-34 (Planck's constant)

These two equations are applied to light in the theory that light is a particle (photon):

E (energy of photon) - Work Function (energy to remove electron from a metal) = Kinetic Energy

When a photon hits a metal surface, it can remove electrons from that metal. The energy of the photon moves to the electron, causing the electron to move.

E = (-hR)/n^2

n = energy level

R = Rydberg Constant = 3.29 * 10^15

Remember, De Brogile Equation is for electrons only. Do not use this equation with light!

Posted: **Sat Oct 12, 2019 9:16 pm**

Natalie Wang 1B wrote:It's important to distinguish between equations that are relevant to light (EM radiation) and quantum movement of electrons. For light specifically, you should pay attention to:

These two equations are applied to light in the theory that light is a wave:

c = λv = 3*10^8 (speed of light = wavelength * frequency)

E=hv (Energy = Planck's constant * frequency)

h = 6.63 * 10^-34 (Planck's constant)

These two equations are applied to light in the theory that light is a particle (photon):

E (energy of photon) - Work Function (energy to remove electron from a metal) = Kinetic Energy

When a photon hits a metal surface, it can remove electrons from that metal. The energy of the photon moves to the electron, causing the electron to move.

E = (-hR)/n^2

n = energy level

R = Rydberg Constant = 3.29 * 10^15

Remember, De Brogile Equation is for electrons only. Do not use this equation with light!

Hey Natalie! That's definitely a great strategy to use: thinking in terms of light VS. electrons. So far I have just been figuring out equations based on variables and what is given, but having another technique to consider is awesome as well! Thanks for sharing!

Posted: **Sat Oct 12, 2019 9:17 pm**

Ariel Fern 3A wrote:Hi Ellis! This is Ariel.

Here's a general list from my notes:

c = λ ν

-- Used to calculate wavelength/frequency

E(photon) = h ν

-- Used to calculate energy per single photon

-- Bohr Frequency Condition: v = ∆E/h; used to calculate frequency

E(photon) = Work Function/Threshold Energy + EK

EK =(1/2)mv^2

-- Used for Photoelectric Effect problems (when an electron is ejected)

En = -(h)(R)/n^2 for n =1,2...

-- Used for electron transitions for the H-atom spectrum

λ = h/p, where p = mass x velocity; λ = h/(mass x velocity)

-- De Broglie Equation: Used to find wavelength/"wavelike properties" of moving objects (only noticeable for objects with extremely small mass)

There is also the Heisenberg Indeterminacy Equation (∆p ∆x ≥ h/4π) and Schrodinger's Equation (Hψ = Eψ), but we haven't covered those yet! Hope this helps! Also, there is a list of constants and equations on the Chem 14A page, and it has helped me keep track of all of these! Let me know if there is a mistake here or if there is an easier way to list these!

This is so helpful, thank you!

Posted: **Sat Oct 12, 2019 10:55 pm**

Anyone have any tips for distinguishing between formulas designated for electrons vs those related to light? I'm having trouble keeping all their meanings and uses straight.

Posted: **Sat Oct 12, 2019 10:58 pm**

A good rule of thumb is that any equation with mass (m) as one of the variables CANNOT be used for light, as light particles (aka photons) have no mass!

Posted: **Sun Oct 13, 2019 12:08 am**

The responses to this post are really helpful. I was looking at my notes but they were somewhat disorganized. This is what I needed for understanding the recent equations from the lectures, so thank you.