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Structure of an Atom

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Atomic structure is fundamental to inorganic chemistry, perhaps more so even than organic chemistry because of the variety of elements and their electron configurations that must be dealt with.

In 1913, Neils Bohr proposed the structure of an atom. According to his concept an atom consists of a central mass called the nucleus, which is surrounded by the orbital electrons, which are negatively charged.

What is the Structure of an Atom?

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Structure of an atom is a key scientific theory. The most surprising feature is that an atom is mostly space.
  1. The mass is concentrated in the middle, in the nucleus, in which is positively charged.
  2. Orbiting round the nucleus but a long way from it are very light, negatively charged particles called electrons.
  3. So it is the attraction between positive charge and negative charge that holds the electrons in place round the atom. the nucleus is composed of two sorts of subatomic particles, protons which each have a positive charge and neutrons which have the same mass as protons but are neutral.
Structure of Atom

Describe the Structure of an Atom

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Atoms consists of very small very dense nucleus with electrons orbiting around it.
  1. The nucleus contains both protons and neutrons.
  2. The number of protons determines the atoms chemical nature; this number is called the atomic number and is given by the symbol Z.
  3. Neutrons and protons carry an attractive force called the strong force to overcome the repulsion between the positively charged protons.
  4. The number of neutrons in an atom can be variable.
  5. The nucleus diameter is only about 1/100000 of the atoms diameter, so much of the volume of the atom consists of empty space.
Atom Model

The structure of a typical atom would have the protons and neutrons in the nucleus or center of the atom and the electrons spinning in a cloud arrangement outside of the nucleus of the atom.

Basic Structure of an Atom

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Atoms are the bases of all substances that are known to exist in the universe. Everything on our earth is made from 96 stable and 12 unstable elements. Each element has a different atomic structure. The basic structure of an atom involves a nucleus and the orbiting electrons.

The nucleus consists of protons and neutrons. The difference in atomic structures results in different properties of the elements. The simplest atomic structure of hydrogen atom is shown below.


Atomic Structure


As can be seen from the diagram the nucleus is located at the core of the atom, whereas the lone electron revolves in an orbit that is away from the nucleus.

Explain the Structure of an Atom

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Matter is made up of atoms. Atoms are made up of protons, neutrons and electrons.
  1. Protons and neutrons are located at the center (or nucleus) of the atom.
  2. Protons have a positive charge.
  3. Neutrons have no charge and have little or no effects as far as electrical are concerned.
  4. Electrons have a negative charge and travel around the nucleus in orbits.
  5. The number of electrons in an atom is the same as the number of protons.
  6. Electrons in the same orbit are the same distance from the nucleus but do not follow the same distance from the nucleus but do not follow the same orbital paths.

The discovery of the components of atoms and the investigation of the structure of atoms constitute one of the most interesting stories in the history of science. It has been discovered that the bonds that hold atoms together in molecules consist of pairs of electrons held jointly by two atoms.

Subatomic Structure of an Atom

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Atoms possess internal structure that is they are made up of even smaller particles which are called subatomic particles. A subatomic particle is a very small particle that is a building block for atoms.

Three types of subatomic particles are found within atoms: electrons, protons and neutrons.
  1. An electron is a subatomic particle that possesses a negative (-) electrical charge. It is the smallest in terms of mass of the three types of subatomic particles.
  2. A proton is a subatomic particle that possesses a positive (+) electrical charge. Protons and electrons carry the same amount of charge the charges however are opposite (positive versus negative).
  3. A neutron is a subatomic particle that has no charge associated with it; that is it is neutral. Both protons and neutrons are massive particles compared to electrons; they are almost 2000 times heavier.

Properties of an Atom

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One of the most fundamental principles of chemistry is the periodic law, which states that "the chemical and physical properties of elements are a periodic function of atomic number."

Periodic table is used to correlate properties on an atomic scale. In particular atomic radius, ionic radius, ionization energy, electron affinity and electronegativity vary horizontally and vertically in the periodic table.

1. Atomic radius

In general atomic radius decreases across a period from left to right in the periodic table and increases down a group in the periodic table.

2. Ionic radius

Ionic radius increases moving down a group in the periodic table. Moreover the radii of both cations and anions decreases from left to right across a period.

3. Ionization energy

It is noticed that ionization energies increases across the periodic table from left to right and decreases moving down the periodic table.

4. Electron affinity

It represent the energy involved in the gain or loss of an electron by an atom, it is not surprising that periodic trends in these properties are also related. Elements having high ionization energies generally has a more negative value for its electron affinity.

5. Electronegativity

The general trend is that electronegativity increases across a period in the periodic table and decreases down a group of the periodic table.
If the total mass involved in a chemical reaction is precisely measured before and after the reaction takes place, the most sensitive balances cannot detect any change. This generalization is known as the law of conservation of mass.
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The idea of atoms was adopted by Dalton in his famous theory known as Dalton's atomic theory. It states that "an atom is a particle indivisible in chemical changes." All substances consist of tiny particles atoms and molecules that is the matter has a discrete structure.
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Isotopes are atoms whose nuclei contain the same number of protons but a different number of neutrons. The term isotopes is derived from Greek and indicates that isotopes occupy the same position in the periodic table.
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Chemists use a convenient unit called mole (mol), which is the number of atoms in a reference sample having a convenient mass to avoid work with unimaginably large numbers. "One mole is the number of atoms in exactly 12g of the pure isotope carbon-12."
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The composition of each element and compound is represented by a symbol or formula. Molecular formula describes the composition of elements but does not provide any information about the structure of that molecule. Molecular formula is a multiple of empirical formula.

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