Chemistry: Atomic Structure and Chemical Bonding: Fundamental Particles of an Atom: Electron, Proton and Neutron

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Fundamental Particles of an Atom: Electron, Proton and Neutron

  • Electrons are defined as the negatively charged particles of an atom. In the atomic nucleus

  • All the electrons of an atom create a negative charge that balances the positive charge of the protons.

  • A proton is a subatomic particle found in the nucleus of every atom. Also the total number of protons in an element’s nucleus is called atomic number.

  • A neutron is an atomic particle that has no electrical charge. It is found in the nucleus of every atom except that of simple hydrogen.

Rutherford’S Nuclear Model

Image of Rutherford's nuclear model

Image of Rutherford's Nuclear Model

Image of Rutherford's nuclear model

  • Rutherford’s atomic model became known as the nuclear model. In the nuclear atom, the protons and neutrons, which comprise nearly all of the mass of the atom, are located in the nucleus at the center of the atom.

  • The electrons are distributed around the nucleus and occupy most of the volume of the atom.

Atomic Number and Mass Number

Image of Atomic Number and Mass Number

Image of Atomic Number and Mass Number

Image of Atomic Number and Mass Number

  • An Atomic Number is the number of protons found in the nucleus of every atom of that element. The atomic number or proton number is represented by symbol Z. For example, the atomic number of nitrogen is 7. This means that each neutral nitrogen atom has 7 protons and 7 electrons.

  • Mass Number is defined as the total number of protons and neutrons in a nucleus. For example, the mass number of fluorine is 19 and the atomic number is 9 (indicating 9 protons in the nucleus). Thus the number of neutrons in an atom of fluorine is

Isotopes and Isobars

Image of Isotopes

Image of Isotopes

Image of Isotopes

Image of Isobars

Image of Isobars

Image of Isobars

  • Isotopes are defined as the atoms with the same number of protons and electrons but different number of neutrons. For eg. Carbon-12, Carbon-13 and Carbon-14 are the three isotopes of Carbon.

  • Isobars are defined as the atoms with same mass number but different atomic number. For e.g. an example of a series of isobars would be 40S, 40Cl, 40Ar, 40K, and 40Ca.

Line Spectrum of H Atom

Image of Line spectrum of H atom

Image of Line Spectrum of H Atom

Image of Line spectrum of H atom

  • There are four lines in the visible spectrum of hydrogen.

  • The light emitted by hydrogen atoms is red because, of its four characteristic lines, the most intense line in its spectrum is in the red portion of the visible spectrum, at 656 nm.

  • On careful analysis of the hydrogen spectrum it was found to consist of a few sets of lines in the ultraviolet, visible and infrared regions. These sets of lines were observed by different scientists. These spectral emission lines could be expressed in the form of a general formula as:

  • Summary of the emission lines observed in Hydrogen Spectrum

Table 1 Supporting: Line spectrum of H atom

Tablutation of: Series, n1 , n2 , Region of Spectrum

Series

Region of Spectrum

Lyman

1

2,3,4

Ultraviolet

Balmer

2

3,4,5

Visible

Paschen

3

4,5,6

Infrared

Bracket

4

5,6,7

Infrared

Pfund

5

6,7,8

Infrared

Bohr’S Model

Image of Bohr's Model

Image of Bohr's Model

Image of Bohr's Model

  • The electrons move in a definite circular path around the nucleus. He called these circular paths as orbits and postulated that as long as the electron is in a given orbit its energy does not change (or energy remains fixed). These orbits were therefore referred to as stationary orbits or stationary states or non-radiating orbits.

  • The electron can change its orbit by absorbing or releasing energy. An electron at a lower (initial) state of energy can go to a higher (final) state of energy, by absorbing a single photon of energy as given by.

Wave Particle Duality and De Broglie Relationship

Wave particle duality and de Broglie relationship

Wave Particle Duality and De Broglie Relationship

Wave particle duality and de Broglie relationship

  • In quantum mechanics, every particle may be partly described in terms not only of particles, but also of waves.

  • It expresses the inability of the classical concepts “particle” or “wave”to fully describe the behavior of quantum-scale objects.

  • De Broglie equation establishes a moving particle’s wavelength with its momentum. He suggested that just like light matter too exhibits wave like and particle like properties.

  • The de Broglie wavelength is defined as the wavelength,, associated with a massive particle being related to its momentum, p, through the Planck constant.

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