Second Chp4 Chem

What did Max Plank observe regarding heating objects and their glow?

When solids are heated, they absorb and emit electromagnetic radiation over a wide range of wavelengths. You add more heat, and it starts to glow.

Radiant energy is emitted by an object at a certain temperature, depending on its wavelength.

How is light measured?

Light energy is emitted or absorbed in discrete units (quanta), NOT consistently.

Other notes about quantum.

Quantum are also whole amounts. Measuring this energy is directed to the frequency.

Equations for energy

E = H x v

Plank’s constant

h = 6.62 × 10-34 J·s. This is a fundamental constant used in the calculation of energy levels in quantum mechanics.

How is matter absorbed or emitted? 

Matter is not emitted or absorbed consistently, but in chunks in quantums.

Above which temperature is a solid giving off light?

0k

Why can’t light given off by these solids be seen?

This can’t be seen at low temperatures because it falls below the visible portion of the spectrum.

Between what temperatures is the object going to turn red?

Regardless of the element at about 700* to 750* C, solids will grow red. Metals get red hot in fire.

What happens when the object keeps on getting hotter?

At higher temperatures, the energy transitions of electrons become more significant, emitting visible light as the solids reach incandescence. It turns blue, and yellow light is emitted until.

At what temp does a substance become white hot?

1200 C

What was Max Plank’s major discovery?

Max Planck saw that energy and frequency of the radiation emitted by these heated objects. Found they were related through a constant value.

Limited quantities = ???

Certain discrete amounts

Smallest amount of energy is called a what?

quantum

Light has both what?

Wave & Particle nature

Photon

Particle of a light

Photoelectricity

Only light with photons that have enough energy (equal to or greater than the metal’s work function, W) can knock electrons off a metal’s surface—this is the photoelectric effect. Red light lacks the needed energy, so no electrons are emitted.

What happens as a result of high energy photons?

knock an electron from a metal atom; this process is more efficient, allowing for a greater number of photoelectrons to be emitted, thus increasing the current in a circuit.

Shorter wavelength =

Longer wavelength =

Higher frequency and higher energy

Lower frequency and lower energy, which means fewer photoelectrons will be emitted from the metal surface.

Wavelength

distance between identical points on successive waves

Frequency (ν)

the number of waves that pass through a particular point in 1 second. How often a eavelnght passes. (Hz = 1 cycle/s)

Speed (c)

All waves travel at the same speed. More waves that pass the more they must be together.

What did maxwell note? 

proposed that visible light consists of electromagnetic waves. Magnetic field moves with electric field bends the path of the wave, resulting in varying properties such as polarization and intensity.

Speed of light c

3.00e⁸m/s

What is frequency measured in?

Hz = wave/s

Formula for electromagnetic waves

ν x λ

Hydrogen Gas Discharge Tube:

When an electric current is passed through the lamp, some of the hydrogen atoms are energized as they are struck by electrons.

Red, green, blue, and violet if seen through a prism. If we pass this light through a prism, we observe narrow lines separated by dark regions.

These energized (excited) atoms give off energy in the form of light.

Emission Spectroscopy

• The analysis of light emitted when an element is strongly heated or energized by an electric current.

• The light is dispersed into individual wavelengths. Monochromatic wavelengths.

• This is the emission spectrum for an element.

• Every element has a unique emission spectrum. A compound is a combination of all those colors.

Neils Bohr Analysis

Bohr combined quantum theory with classical physics to explain hydrogen’s structure. Electrons occupy fixed energy levels, and when they drop to lower levels, they emit photons that produce distinct spectral lines. Their circular motion keeps them stable and prevents them from crashing into the positively charged nucleus.

Neils Bohr Analysis 2

Bohr proposed that an electron’s angular momentum is quantized—it can only have specific energy levels. While in a fixed orbit, it neither gains nor loses energy, preventing it from falling into the nucleus. His “solar system” model pictured electrons orbiting like planets, where higher speeds mean farther orbits.

Matter, at least in this unit, can what?

Matter can observe or emit certain values of energy.  

Main idea for Einstein 

light energy is quantized.  it has fixed amount of energy.  Light energy is precise as well. 

Shorter wavelength means what?

more deflection and higher energy photons.

Johan Balmer

helped Bohr describe the energy levels in which electrons could exist.   Initial is where its falling from and its super energized and falls down to another orbit, It gives off photon with a different wavelength.

Rydberg formula 

E = E_f - E_i = 2.18e^-18J(1/n_i² - 1/n_f²)

Nature of Energy:

• Niels Bohr adopted Planck’s assumption and explained these phenomena in this way: Electrons in an atom can only occupy certain orbits.  Energy is absorbed or emitted in such a way as to move an electron from one allowed energy state to another, the energy is defined by (E = hV). Electrons cannot orbit in between.   

• It will always give off the same photon, regardless of where it falls. 

What did Bohr calculate?

Bohr calculated the energy that an electron has on each energy level.  

Notes for force & such

The lower (more negative) the energy, the more stable the atom will be. Closer to the nucleus, the force and attraction will be.  

What happens to the radius and the energy as n becomes infinitely large?

• Radius increases & electron is separated from the nucleus 

• Bohr postulated that aelectrons could ju,p from one energy state to antoerh by absorbing or emitting photons whose radiant energy corresponds exactly to the energy difference between the two states.  It must absorb enough energy that is equal to the difference of energy in the two orbits.  

the relationship between the frequency of light and the energy of the light was postulated by ?

Max Planck.

Photonic effect

which electromagnetic wave is 1.0e-3

microwave

what is the emission of light at only specific wavelengths

is called atomic emission spectrum.

A bright-line spectrum of an atom is caused by the energy released electrons

B)fall to a lower energy level

Bohr's model of the atom works best in explaining

B) only the spectra of hydrogen and not more complex atoms.

According to the Bohr model of the atom, the singly electron of a hydrogen atom circles the nucleus 

A)in specific, allowed orbits

Highest energy photon are what numbers

6-1

Rydberg equations is a relationship between

A) the relationship between wavelengths of spectral lines and the electrons energies responsible for them

E = ??

2.18e^-18 J/n²

The energy is negative for all values of

n

Why doesn’t this work?

• Electrons do not orbit the nucleus in fixed energy orbits

• If light has particle-like properties.   

• **** Maybe particles can also exhibit wave-like properties.

• Electrons’ energy is allowed to certain amounts, which is why the energy that shape is transformed is always the same.    

What experiment proved the wave and light properties?

double slit experiment 

Bohr model history

Even though he invoked the concept of quantum, his theory was primarily based on classical physics.  

Absorb =

Emmit = 

+, -

Highest wavelength for hydrogen

red

Uncertainty Principle

It’s impossible to accurately determine the exact position of and momentum (velocity) of an electron at the same time.