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 one atom have the right to be figured out from a collection of an easy rules.

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

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


12C 13C 14C 14N

The various isotopes of an facet are established by composing the mass variety of the atom in the top left corner of the symbol for the element. 12C, 13C, and 14C room isotopes that carbon (Z = 6) and therefore contain 6 protons. If the atoms are neutral, they likewise must contain 6 electrons. The just difference in 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 neutrons

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


Practice problem 1:

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

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Electromagnetic Radiation

Much of what is known about the framework of the electrons in one atom has been obtained by studying the interaction between matter and different creates of electromagnetic radiation. Electromagnetic radiation has some the 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 also yet they bring energy as they travel through space. In addition 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) per unit the time. The frequency the a tide is reported in units of cycles per second (s-1) or hertz (Hz).

The idealized drawing of a tide in the figure listed below illustrates the meanings of amplitude and wavelength. The wavelength (l) is the smallest distance between repeating points on the wave. The amplitude of the tide is the distance between the highest (or lowest) allude on the wave and also the center of heaviness of the wave.

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

vl = s


Practice problem 2:

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

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Practice problem 3:

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

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Light and also Other forms of Electromagnetic Radiation

Light is a wave with both electric and also magnetic components. It is therefore a kind of electromagnetic radiation.

Visible light includes the small band that frequencies and also wavelengths in the part of the electro-magnetic spectrum the our eyes deserve to 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, irradiate is bent once it enters a glass prism. When white light is focused on a prism, the irradiate 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 where the irradiate is bent by the the smallest angle, the colors space red, orange, yellow, green, blue, and violet.

As we deserve to see indigenous the following diagram, the energy carried by light increases as us go native red come blue throughout the clearly shows spectrum.

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Because the wavelength that electromagnetic radiation can be as lengthy as 40 m or as brief as 10-5 nm, the clearly shows spectrum is only a small portion of the total variety of electromagnetic radiation.

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The electromagnetic spectrum has radio and TV waves, microwaves, infrared, clearly shows light, ultraviolet, x-rays, g-rays, and cosmic rays, as presented in the number above. These different forms of radiation all travel at the speed of light (c). Castle differ, however, in your frequencies and wavelengths. The product that the frequency times the wavelength of electromagnetic radiation is constantly equal come the speed of light.

vl = c

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


Practice difficulty 4:

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