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 electrons in an atom deserve to be determined from a collection of simple rules.

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

Examples: Let"s recognize the variety of protons, neutrons, and also electrons in the complying with isotopes.

12C 13C 14C 14N

The various isotopes that an facet 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 room isotopes the carbon (Z = 6) and also therefore contain 6 protons. If the atoms space neutral, they also must contain six electrons. The just difference between these isotope is the number of neutrons in the nucleus.

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

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

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

Practice problem 1:

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

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Electromagnetic Radiation

Much of what is known around the framework of the electrons in one atom has actually been acquired by examining the interaction between matter and also 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 they accounting space. Waves have no mass and also yet they lug energy together they travel with space. In addition to their capability to carry energy, tide have four other properties properties: speed, frequency, wavelength, and amplitude. The frequency (v) is the variety of waves (or cycles) every unit that time. The frequency the a wave is report in units of cycles per second (s-1) or hertz (Hz).

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


If us measure the frequency (v) of a wave in cycles per 2nd and the wavelength (l) in meters, the product the these two numbers has actually the systems of meters every second. The product the the frequency (v) times the wavelength (l) that a wave is thus the rate (s) in ~ which the wave travels v space.

vl = s

Practice problem 2:

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

Click right here to inspect your answer come Practice difficulty 2

Practice trouble 3:

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

Click here to examine your answer come Practice difficulty 3

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Light and also Other develops of Electromagnetic Radiation

Light is a wave through both electric and magnetic components. The is as such a kind of electromagnetic radiation.

Visible light contains the small band that frequencies and wavelengths in the portion of the electro-magnetic spectrum that our eyes have the right to detect. It contains radiation with wavelengths between around 400 nm (violet) and also 700 nm (red). Due to the fact that it is a wave, irradiate is bent when it beginning a glass prism. As soon as white irradiate is concentrated on a prism, the irradiate rays of various wavelengths room bent by differing quantities and the light is transformed into a spectrum that colors. Starting from the side of the spectrum whereby the light is bending by the the smallest angle, the colors room red, orange, yellow, green, blue, and also violet.

As we deserve to see indigenous the adhering to diagram, the energy lugged by light boosts as us go indigenous red to blue across the visible spectrum.


Because the wavelength the electromagnetic radiation can be as lengthy as 40 m or as brief as 10-5 nm, the clearly shows spectrum is only a small part of the total variety 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 shown in the figure above. These various forms the radiation all take trip at the rate of irradiate (c). They differ, however, in your frequencies and also wavelengths. The product the the frequency times the wavelength that electromagnetic radiation is always equal come the speed of light.

vl = c

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

Practice difficulty 4:

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