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 variety of protons, neutrons, and also electrons in an atom can be figured out from a set of simple rules.

The number of protons in the cell core of the atom is same 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 sum of the number of protons and neutrons in the nucleus. The variety of neutrons is equal to the difference between the mass variety of the atom (M) and the atom number (Z).

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


12C 13C 14C 14N

The different isotopes that an facet are identified by creating the mass number of the atom in the upper left corner of the symbol for the element. 12C, 13C, and also 14C space isotopes the carbon (Z = 6) and therefore contain 6 protons. If the atoms space neutral, they additionally must contain six electrons. The just difference 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 7 neutron

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


Practice problem 1:

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

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Electromagnetic Radiation

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

Particles have actually a identify mass and they occupy space. Waves have no mass and yet they carry energy together they travel through space. In enhancement to their capability to lug energy, tide have 4 other properties properties: speed, frequency, wavelength, and amplitude. The frequency (v) is the variety of waves (or cycles) every unit that time. The frequency of a tide is report in units of cycles per second (s-1) or hertz (Hz).

The idealized drawing of a wave 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) suggest on the wave and also the center of heaviness of the wave.

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

vl = s


Practice difficulty 2:

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

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Practice problem 3:

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

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Light and also Other forms of Electromagnetic Radiation

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

Visible light has the narrow band the frequencies and also wavelengths in the portion of the electro-magnetic spectrum the our eyes deserve to detect. It has radiation with wavelengths between about 400 nm (violet) and 700 nm (red). Because it is a wave, light is bent when it beginning a glass prism. As soon as white light is focused on a prism, the light rays of various wavelengths room bent by differing quantities and the irradiate is transformed into a spectrum the colors. Beginning from the side of the spectrum whereby the light is bent by the smallest angle, the colors room red, orange, yellow, green, blue, and also violet.

As we can see from the complying with diagram, the energy brought by light rises as us go native red to blue throughout the visible spectrum.

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

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The electromagnetic spectrum includes radio and also TV waves, microwaves, infrared, clearly shows light, ultraviolet, x-rays, g-rays, and also cosmic rays, as shown in the figure above. These various forms that radiation all travel at the speed of light (c). They differ, however, in their frequencies and also wavelengths. The product of the frequency time the wavelength of electromagnetic radiation is always equal to the rate of light.

vl = c

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


Practice trouble 4:

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