The Atom and Electromagnetic Radiation




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Fundapsychological Subatomic Particles Electromagnetic Radiation
Light and also Other Forms of Electromagnetic Radiation

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

The variety of protons, neutrons, and electrons in an atom deserve to be figured out from a set of basic rules.

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

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


12C 13C 14C 14N

The different isotopes of an aspect are determined by composing the mass variety of the atom in the upper left corner of the symbol for the element. 12C, 13C, and 14C are isotopes of carbon (Z = 6) and therefore contain six protons. If the atoms are neutral, they additionally must contain 6 electrons. The just difference in between these isotopes is the variety of neutrons in the nucleus.

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

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

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


Practice Problem 1:

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

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Electromagnetic Radiation

Much of what is recognized about the structure of the electrons in an atom has been obtained by studying the interaction in between issue and also different develops of electromagnetic radiation. Electromagnetic radiation has some of the properties of both a ppost and a wave.

Particles have actually a definite mass and also they occupy space. Waves have no mass and yet they bring energy as they travel via space. In enhancement to their capacity to carry power, waves have actually four other characteristic properties: rate, frequency, wavesize, and also amplitude. The frequency (v) is the variety of waves (or cycles) per unit of time. The frequency of a wave 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 meanings of amplitude and also wavesize. The wavelength (l) is the smallest distance between repeating points on the wave. The amplitude of the wave is the distance between the greatest (or lowest) allude on the wave and the facility of gravity of the wave.

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If we measure the frequency (v) of a wave in cycles per second and also the wavelength (l) in meters, the product of these two numbers has actually the units of meters per second. The product of the frequency (v) times the wavelength (l) of a wave is therefore the speed (s) at which the wave travels through area.

vl = s


Practice Problem 2:

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

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Practice Problem 3:

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

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Click here to check out a solution to Practice Problem 3




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Light and also Other Forms of Electromagnetic Radiation

Light is a wave via both electrical and magnetic components. It is therefore a form of electromagnetic radiation.

Visible light consists of the narrowhead band also of frequencies and also wavelengths in the portion of the electro-magnetic spectrum that our eyes deserve to detect. It consists of radiation with wavelengths in between around 400 nm (violet) and also 700 nm (red). Due to the fact that it is a wave, light is bent when it enters a glass prism. When white light is focused on a prism, the light rays of various wavelengths are bent by differing quantities and also the light is transformed into a spectrum of colors. Starting from the side of the spectrum where the light is bent by the smallest angle, the colors are red, oselection, yellow, green, blue, and also violet.

As we deserve to see from the complying with diagram, the energy lugged by light increases as we go from red to blue across the visible spectrum.

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Due to the fact that 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 only a little percentage of the total variety of electromagnetic radiation.

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The electromagnetic spectrum contains radio and TV waves, microwaves, infrared, visible light, ultraviolet, x-rays, g-rays, and cosmic rays, as shown in the figure over. These various forms of radiation all travel at the rate of light (c). They differ, yet, in their frequencies and also wavelengths. The product of 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 a lengthy wavelength has actually a low frequency, and also radiation with a high frequency has a short wavesize.


Practice Problem 4:

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