The Atom and Electromagnetic Radiation

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Fundamental Subatomic Particles Electromagnetic Radiation
Light and 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 one atom deserve to be determined from a set of an easy rules.

The number 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 equal to the number of protons. The mass number 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 equal to the difference in between the mass number of the atom (M) and also the atomic number (Z).

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

12C 13C 14C 14N

The different isotopes the an element are identified by creating the mass number of the atom in the top left corner of the symbol for the element. 12C, 13C, and 14C space isotopes that carbon (Z = 6) and therefore contain six protons. If the atoms room neutral, they likewise must contain six electrons. The only difference between these isotope is the number 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 8 neutrons

Practice trouble 1:

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

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Electromagnetic Radiation

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

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

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


If us measure the frequency (v) the a wave in cycles per 2nd and the wavelength (l) in meters, the product that these two numbers has the units of meters per second. The product that the frequency (v) times the wavelength (l) that a wave is as such the rate (s) in ~ 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 trouble 3:

Orchestras in the United says 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 of this note?

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Light and also Other develops of Electromagnetic Radiation

Light is a wave through both electric and also magnetic components. It is thus a form of electromagnetic radiation.

Visible light has the narrow band of frequencies and also wavelengths in the section of the electro-magnetic spectrum that our eyes deserve to detect. It contains radiation through wavelengths between around 400 nm (violet) and also 700 nm (red). Because it is a wave, light is bent once it start a glass prism. As soon as white light is focused on a prism, the irradiate rays of various wavelengths space bent through differing amounts and the irradiate is transformed into a spectrum that colors. Beginning from the side of the spectrum wherein the light is bend by the smallest angle, the colors space red, orange, yellow, green, blue, and also violet.

As we can see from the adhering to diagram, the energy carried by light rises as us go indigenous red come blue throughout the clearly shows spectrum.


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


The electromagnetic spectrum consists of 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 various forms the radiation all travel at the rate of irradiate (c). Castle differ, however, in your frequencies and wavelengths. The product that the frequency times the wavelength that electromagnetic radiation is constantly equal come 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 a quick wavelength.

Practice trouble 4:

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