The Atom and Electromagnetic Radiation

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Fundamental Subatomic Particles Electromagnetic Radiation
Light and also Other forms of Electromagnetic Radiation

Particle Symbol Charge Mass
electron e- -1 0.0005486 amu
proton p+ +1 1.007276 amu
neutron no 0 1.008665 amu

The number of protons, neutrons, and also electrons in one atom have the right to be determined from a collection of straightforward rules.

The variety of protons in the cell core of the atom is equal to the atom number (Z). The variety of electrons in a neutral atom is same to the variety of protons. The mass variety of the atom (M) is same to the amount of the number of protons and also neutrons in the nucleus. The number of neutrons is same to the difference between the mass variety of the atom (M) and the atom number (Z).

Examples: Let"s recognize the number of protons, neutrons, and electrons in the complying with isotopes.

12C 13C 14C 14N

The different isotopes the an element are established by creating the mass variety of the atom in the top left corner of the symbol because that the element. 12C, 13C, and also 14C space isotopes that carbon (Z = 6) and therefore contain 6 protons. If the atoms space neutral, they likewise must contain six electrons. The only difference in between these isotope is the variety of neutrons in the nucleus.

12C: 6 electrons, 6 protons, and 6 neutrons

13C: 6 electrons, 6 protons, and also 7 neutrons

14C: 6 electrons, 6 protons, and also 8 neutrons

Practice problem 1:

Calculate the variety of electrons in the Cl- and also Fe3+ ions.

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Electromagnetic Radiation

Much the what is known around the structure of the electrons in one atom has been acquired by researching the interaction between matter and different creates of electromagnetic radiation. Electromagnetic radiation has some of the nature of both a particle and also a wave.

Particles have a definite mass and they accounting space. Waves have actually no mass and yet they lug energy as they travel v space. In addition to their capacity to lug energy, waves have 4 other characteristic properties: speed, frequency, wavelength, and amplitude. The frequency (v) is the number of waves (or cycles) per unit the time. The frequency of a wave is reported in units of cycles per 2nd (s-1) or hertz (Hz).

The idealized illustration of a tide in the figure below illustrates the interpretations of amplitude and wavelength. The wavelength (l) is the the smallest distance in between repeating point out on the wave. The amplitude the the tide is the distance in between the greatest (or lowest) suggest on the wave and also the center of heaviness of the wave.


If us measure the frequency (v) that a wave in cycles per second and the wavelength (l) in meters, the product that these two numbers has the units of meters per second. The product the the frequency (v) times the wavelength (l) the a wave is as such the speed (s) in ~ which the wave travels with space.

vl = s

Practice trouble 2:

What is the rate of a wave that has a wavelength the 1 meter and also a frequency that 60 cycles per second?

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Practice problem 3:

Orchestras in the United claims tune their tools to one "A" that has a frequency of 440 cycles every second, or 440 Hz. If the speed of sound is 1116 feet per second, what is the wavelength the this note?

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Light and Other creates of Electromagnetic Radiation

Light is a wave with both electric and magnetic components. It is because of this a type of electromagnetic radiation.

Visible light contains the small band of frequencies and wavelengths in the part of the electro-magnetic spectrum the our eyes can detect. It contains radiation v wavelengths between about 400 nm (violet) and 700 nm (red). Due to the fact that it is a wave, irradiate is bent once it start a glass prism. Once white light is focused on a prism, the light rays of various wavelengths room bent by differing amounts and the light is transformed right into a spectrum of colors. Beginning from the side of the spectrum where the irradiate is bending by the smallest angle, the colors are red, orange, yellow, green, blue, and violet.

As we can see indigenous the complying with diagram, the energy brought by light boosts as us go from red come blue throughout the clearly shows spectrum.


Because the wavelength of electromagnetic radiation have the right to be as lengthy as 40 m or as short as 10-5 nm, the visible spectrum is just a small portion of the total variety of electromagnetic radiation.


The electromagnetic spectrum has radio and also TV waves, microwaves, infrared, visible light, ultraviolet, x-rays, g-rays, and also cosmic rays, as displayed in the figure above. These different forms that radiation all take trip at the speed of irradiate (c). They differ, however, in their frequencies and wavelengths. The product the the frequency times the wavelength of electromagnetic radiation is constantly equal to the rate of light.

vl = c

As a result, electromagnetic radiation that has actually a lengthy wavelength has a low frequency, and also radiation v a high frequency has actually a short wavelength.

Practice trouble 4:

Calculate the frequency the red irradiate that has a wavelength of 700.0 nm if the rate of irradiate is 2.998 x 108 m/s.