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 also electrons in one atom deserve to be identified from a set of straightforward rules.

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

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


12C 13C 14C 14N

The various isotopes the an element are determined by writing the mass variety of the atom in the upper left edge of the symbol because that the element. 12C, 13C, and also 14C are isotopes that carbon (Z = 6) and also therefore contain 6 protons. If the atoms room neutral, they also must contain six electrons. The just 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 neutron

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


Practice difficulty 1:

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

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Electromagnetic Radiation

Much the what is known around the framework of the electrons in one atom has been derived by examining the interaction between matter and different forms of electromagnetic radiation. Electromagnetic radiation has some of the properties of both a particle and also a wave.

Particles have actually a identify mass and also they accounting space. Waves have actually no mass and yet they lug energy together they travel with space. In addition to their capability to carry energy, waves have 4 other characteristic properties: speed, frequency, wavelength, and also amplitude. The frequency (v) is the variety of waves (or cycles) every unit of time. The frequency the a tide is reported in units of cycles per second (s-1) or hertz (Hz).

The idealized drawing of a wave in the figure below illustrates the definitions of amplitude and also wavelength. The wavelength (l) is the smallest distance in between repeating clues on the wave. The amplitude of the tide is the distance in between the highest possible (or lowest) allude on the wave and the center of gravity of the wave.

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If us measure the frequency (v) of a tide in cycles per second and the wavelength (l) in meters, the product that these 2 numbers has the systems of meters per second. The product that the frequency (v) times the wavelength (l) of a tide is thus the speed (s) at which the wave travels v space.

vl = s


Practice problem 2:

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

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Practice problem 3:

Orchestras in the United states tune their instruments to an "A" that has a frequency that 440 cycles per 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 also Other forms 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 has the narrow band the frequencies and wavelengths in the section of the electro-magnetic spectrum the our eyes can detect. It consists of radiation with wavelengths between about 400 nm (violet) and also 700 nm (red). Because it is a wave, irradiate is bent when it beginning a glass prism. Once white irradiate is focused on a prism, the irradiate rays of different wavelengths are bent through differing quantities and the irradiate is transformed right into a spectrum the colors. Beginning from the next of the spectrum where the irradiate is bending by the the smallest angle, the colors space red, orange, yellow, green, blue, and violet.

As we can see indigenous the following diagram, the energy lugged by light increases as we go native red to blue across the visible spectrum.

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Because the wavelength the electromagnetic radiation can be as lengthy as 40 m or as brief as 10-5 nm, the visible spectrum is only a small part of the total range of electromagnetic radiation.

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

vl = c

As a result, electromagnetic radiation that has a lengthy wavelength has a short frequency, and radiation with a high frequency has actually a brief wavelength.


Practice trouble 4:

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