The Atom and Electromagnetic Radiation

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Fundamental Subatomic Particles Electromagnetic Radiation
Light and also 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 an atom can be figured out from a collection of straightforward rules.

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

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

12C 13C 14C 14N

The different isotopes the an facet are figured out by writing the mass variety of the atom in the upper left edge of the symbol for the element. 12C, 13C, and also 14C space isotopes of carbon (Z = 6) and also therefore contain 6 protons. If the atoms are neutral, they also must contain six electrons. The just difference in between these isotope is the variety 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 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 about the structure of the electrons in one atom has been obtained by studying the interaction in between matter and also different creates of electromagnetic radiation. Electromagnetic radiation has some the the nature of both a particle and a wave.

Particles have actually a identify mass and also they occupy space. Waves have actually no mass and also yet they bring energy together they travel v space. In enhancement to their ability to bring energy, waves have four other characteristics properties: speed, frequency, wavelength, and amplitude. The frequency (v) is the variety of waves (or cycles) per unit that time. The frequency of a tide is reported in units of cycles per 2nd (s-1) or hertz (Hz).

The idealized illustration of a tide in the figure below illustrates the meanings of amplitude and also wavelength. The wavelength (l) is the smallest distance in between repeating point out on the wave. The amplitude the the wave is the distance in between the highest (or lowest) point on the wave and the facility of heaviness of the wave.


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

vl = s

Practice trouble 2:

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

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Practice difficulty 3:

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

Click below to check your answer come Practice trouble 3

Click below to view a systems to Practice problem 3

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Light and Other forms of Electromagnetic Radiation

Light is a wave through both electric and magnetic components. The is because of this a type of electromagnetic radiation.

Visible light consists of the small band of frequencies and wavelengths in the portion of the electro-magnetic spectrum the our eyes can detect. It consists of radiation through wavelengths between about 400 nm (violet) and 700 nm (red). Because it is a wave, light is bent as soon as it enters a glass prism. As soon as white irradiate is focused on a prism, the irradiate rays of different wavelengths space bent by differing quantities and the irradiate is transformed right into a spectrum the colors. Starting from the next of the spectrum whereby the irradiate is bending by the smallest angle, the colors room red, orange, yellow, green, blue, and also violet.

As we can see from the adhering to diagram, the energy brought by light rises as us go from red come blue across the visible spectrum.


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


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

vl = c

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

Practice problem 4:

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