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 electrons in an atom deserve to be figured out from a set of straightforward rules.

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

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

12C 13C 14C 14N

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

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

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

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

Practice difficulty 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 framework of the electron in an atom has been obtained by researching the interaction in between matter and different develops of electromagnetic radiation. Electromagnetic radiation has some the the nature of both a particle and also a wave.

Particles have a definite mass and also they accounting space. Waves have actually no mass and yet they carry energy together they travel v space. In enhancement to their capacity to carry energy, tide have four other properties 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 report in systems of cycles per second (s-1) or hertz (Hz).

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


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

vl = s

Practice problem 2:

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

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Practice difficulty 3:

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

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Light and Other forms of Electromagnetic Radiation

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

Visible light consists of the narrow band that frequencies and also wavelengths in the section of the electro-magnetic spectrum the our eyes can detect. It has radiation v wavelengths between around 400 nm (violet) and also 700 nm (red). Due to the fact that it is a wave, light is bent as soon as it enters a glass prism. When white irradiate is concentrated on a prism, the irradiate rays of different wavelengths space bent by differing quantities and the irradiate is transformed right into a spectrum of colors. Beginning from the side of the spectrum where the light is bent by the smallest angle, the colors space red, orange, yellow, green, blue, and violet.

As we can see from the adhering to diagram, the energy lugged by light rises as we go native red to blue across the clearly shows spectrum.


Because the wavelength of electromagnetic radiation deserve to be as long as 40 m or as quick as 10-5 nm, the clearly shows spectrum is only a small portion of the total selection of electromagnetic radiation.


The electromagnetic spectrum has radio and also TV waves, microwaves, infrared, clearly shows light, ultraviolet, x-rays, g-rays, and also cosmic rays, as displayed in the figure above. These different forms the radiation all take trip at the speed of light (c). Castle differ, however, in their frequencies and also 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 a lengthy wavelength has actually a low frequency, and also radiation with a high frequency has actually a brief wavelength.

Practice difficulty 4:

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