The Atom and also Electromagnetic Radiation

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Fundamental Subatomic Particles Electromagnetic Radiation
Light and 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 also electrons in an atom have the right to be determined from a collection of straightforward rules.

The variety of protons in the cell core of the atom is equal to the atom number (Z). The number of electrons in a neutral atom is same to the number 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 the atom number (Z).

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

12C 13C 14C 14N

The various isotopes of an element are established by writing the mass number of the atom in the top left corner of the symbol because that the element. 12C, 13C, and also 14C space isotopes of carbon (Z = 6) and also therefore contain six protons. If the atoms space neutral, they likewise must contain six electrons. The just 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 7 neutrons

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

Practice trouble 1:

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

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Electromagnetic Radiation

Much the what is known about the structure of the electrons in an atom has been derived by researching the interaction between matter and different creates of electromagnetic radiation. Electromagnetic radiation has some that the properties of both a particle and also a wave.

Particles have actually a identify mass and also they accounting space. Waves have no mass and yet they bring energy together they travel through space. In addition to their capability to bring energy, tide have 4 other characteristic properties: speed, frequency, wavelength, and also amplitude. The frequency (v) is the variety of waves (or cycles) every unit that time. The frequency that a tide is reported in devices of cycles per 2nd (s-1) or hertz (Hz).

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


If we measure the frequency (v) that a tide in cycles per 2nd and the wavelength (l) in meters, the product that these 2 numbers has actually the systems of meters every second. The product of the frequency (v) time the wavelength (l) that a tide is as such the rate (s) in ~ which the wave travels through space.

vl = s

Practice problem 2:

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

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Practice difficulty 3:

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

Click below to check your answer come Practice problem 3

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Light and Other develops of Electromagnetic Radiation

Light is a wave with both electric and also magnetic components. The is because of this a kind of electromagnetic radiation.

Visible light includes the narrow band of frequencies and also wavelengths in the section of the electro-magnetic spectrum the our eyes have the right to detect. It consists of radiation v wavelengths between about 400 nm (violet) and 700 nm (red). Due to the fact that it is a wave, irradiate is bent as soon as it beginning a glass prism. As soon as white irradiate is concentrated on a prism, the light rays of various wavelengths space bent through differing quantities and the light is transformed into a spectrum of colors. Starting from the next of the spectrum where the light is bend by the the smallest angle, the colors are red, orange, yellow, green, blue, and also violet.

As we deserve to see from the complying with diagram, the energy carried by light increases as us go from red come blue across the clearly shows spectrum.


Because the wavelength that electromagnetic radiation have the right to be as long as 40 m or as brief as 10-5 nm, the clearly shows spectrum is only a small section of the total selection of electromagnetic radiation.


The electromagnetic spectrum contains radio and also TV waves, microwaves, infrared, visible 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). They differ, however, in their frequencies and wavelengths. The product the the frequency time the wavelength the electromagnetic radiation is always equal come the rate of light.

vl = c

As a result, electromagnetic radiation that has a long wavelength has a low frequency, and also radiation v a high frequency has actually a quick wavelength.

Practice problem 4:

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