The Atom and 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 electrons in one atom have the right to be established from a set of straightforward rules.

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

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

12C 13C 14C 14N

The different isotopes that an facet are identified by composing the mass number of the atom in the upper left edge of the symbol for the element. 12C, 13C, and also 14C room isotopes of carbon (Z = 6) and therefore contain six protons. If the atoms space neutral, they additionally must contain six electrons. The only difference in between these isotopes is the variety of neutrons in the nucleus.

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

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

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

Practice trouble 1:

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

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Electromagnetic Radiation

Much of what is known around the structure of the electrons in an atom has been derived by examining the interaction between matter and different develops 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 actually no mass and also yet they lug energy together they travel through space. In addition to their capacity to carry energy, tide have 4 other characteristics properties: speed, frequency, wavelength, and also amplitude. The frequency (v) is the variety of waves (or cycles) per unit of time. The frequency that a wave is reported in units of cycles per second (s-1) or hertz (Hz).

The idealized drawing of a tide in the figure below illustrates the interpretations of amplitude and wavelength. The wavelength (l) is the the smallest distance in between repeating clues on the wave. The amplitude the the tide is the distance in between the greatest (or lowest) point on the wave and also the center 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 of these two numbers has the units of meters per second. The product that the frequency (v) times the wavelength (l) the a wave is therefore the rate (s) in ~ which the wave travels v space.

vl = s

Practice trouble 2:

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

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Practice difficulty 3:

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

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Light and also Other creates of Electromagnetic Radiation

Light is a wave v both electric and magnetic components. That 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 that our eyes deserve to detect. It consists of radiation v wavelengths between about 400 nm (violet) and also 700 nm (red). Since it is a wave, light is bent as soon as it enters a glass prism. Once white light is focused on a prism, the irradiate rays of different wavelengths are bent through differing quantities and the irradiate is transformed into a spectrum of colors. Starting from the side of the spectrum wherein the light is bend by the the smallest angle, the colors room red, orange, yellow, green, blue, and violet.

As we can see indigenous the complying with diagram, the energy lugged by light boosts as we go native red come blue throughout the visible spectrum.


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


The electromagnetic spectrum includes radio and also TV waves, microwaves, infrared, visible light, ultraviolet, x-rays, g-rays, and cosmic rays, as presented in the number above. These various forms that radiation all take trip at the rate of light (c). Lock differ, however, in your frequencies and wavelengths. The product the the frequency times the wavelength the electromagnetic radiation is constantly equal to the rate of light.

vl = c

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

Practice problem 4:

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