The Atom and also Electromagnetic Radiation




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Fundamental Subatomic Particles Electromagnetic Radiation
Light and also Other develops 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 electrons in an atom can be identified from a collection of basic rules.

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

Examples: Let"s identify the number of protons, neutrons, and also electrons in the following isotopes.


12C 13C 14C 14N

The various isotopes the an aspect are figured out by composing 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 also therefore contain six protons. If the atoms room neutral, they additionally must contain six electrons. The just difference between these isotopes is the variety of neutrons in the nucleus.

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

13C: 6 electrons, 6 protons, and 7 neutron

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 that what is known about the structure of the electron in an atom has been acquired by researching the interaction between matter and different develops of electromagnetic radiation. Electromagnetic radiation has actually some that the properties of both a particle and also a wave.

Particles have actually a definite mass and also they accounting space. Waves have no mass and yet they carry energy together they travel through space. In addition to their capability to lug energy, tide have four other properties properties: speed, frequency, wavelength, and also amplitude. The frequency (v) is the number of waves (or cycles) every unit of time. The frequency of a tide is reported in devices of cycles per second (s-1) or hertz (Hz).

The idealized drawing of a wave in the figure below illustrates the interpretations of amplitude and also wavelength. The wavelength (l) is the the smallest distance in between repeating points on the wave. The amplitude that the wave is the distance between the highest (or lowest) suggest on the wave and the facility of heaviness of the wave.

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If us measure the frequency (v) the a tide in cycles per second and the wavelength (l) in meters, the product the these two numbers has the systems of meters every second. The product of the frequency (v) time the wavelength (l) the a tide is thus the rate (s) in ~ which the tide travels with space.

vl = s


Practice trouble 2:

What is the speed of a wave that has actually a wavelength of 1 meter and a frequency of 60 cycles every second?

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Practice trouble 3:

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

Click here to check your answer come Practice difficulty 3

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Light and Other creates of Electromagnetic Radiation

Light is a wave v both electric and also magnetic components. That is because of this a form of electromagnetic radiation.

Visible light consists of the small band the frequencies and wavelengths in the portion of the electro-magnetic spectrum that our eyes deserve to detect. It consists of radiation through wavelengths between around 400 nm (violet) and 700 nm (red). Since it is a wave, light is bent when it beginning a glass prism. Once white irradiate is focused on a prism, the irradiate rays of different wavelengths space bent by differing amounts and the irradiate is transformed into a spectrum the colors. Starting from the next of the spectrum wherein 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 rises as we go from red to blue across the visible spectrum.

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Because the wavelength that electromagnetic radiation can be as lengthy as 40 m or as quick as 10-5 nm, the visible spectrum is just a small section of the total selection of electromagnetic radiation.

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The electromagnetic spectrum consists of radio and also TV waves, microwaves, infrared, visible light, ultraviolet, x-rays, g-rays, and cosmic rays, as displayed in the number above. These various forms of radiation all travel at the rate of light (c). Lock differ, however, in their frequencies and wavelengths. The product of the frequency times the wavelength of electromagnetic radiation is constantly equal to the speed of light.

vl = c

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


Practice difficulty 4:

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