## John Dalton's atomic theory to Today's structure

John Dalton’s atomic theory given the primary basis of chemistry. But present-day electrons holds the key to the chemical structure. Thus for better understanding the atomic properties of an element we need to know about their electronic configuration.

Dalton’s atomic theory based on the following assumption

1. Matter made of atoms is indivisible and indestructible.
2. All the atoms of a given element are identical mass and properties.
3. Compounds formed by the combination of two or more same or different kinds of atoms.
4. A chemical reaction is a rearrangement of atoms.

### Limitations of Dalton's atomic theory

The journey from John Dalton’s atomic theory to the modern structure of an atom is a long and arduous one.

He considered the atom was the smallest building block of matter and nothing smaller exist. But as we turn this century many valuable pieces of information given about atomic structure.

It clearly indicated that Dalton’s atomic theory did not grant to its position. Today an atom composed further subatomic particles like electron, proton, and neutron.

### Rutherford atomic structure

Thus Rutherford has remarked that it is not in the nature of things for any one man to make the sudden violet discovery.

Science goes step by step and every man depends on the work of his predecessor. Thus this century Rutherford has given valuable information about atomic structure.

Rutherford alpha particle scattering experiment provides the two most valuable information about the atomic model.

1. All the positive charge and the almost entire mass of an atom concentrated in a very small central core. He named this part as a nucleus.
2. The nucleus of an atom surrounded by negatively charged particles carrying negligible mass, called electrons arranged in a definite order.

### Components of environmental chemistry

#### Nails Bohr's atomic theory

Rutherford model was not in conformity with the classical model of electromagnetic spectrum. The moving charged particle will continuously emit radiation. Thus it continuously loses kinetic energy and eventually hits the nucleus of an atom. To resolve this Niels Bhors proposed an atomic structure based on the following postulates.

1. An atom possesses several stable circular orbits in which an electron can stay. So long as an electron can stay in a particular orbit there is no emission or absorption of energy.
2. An electron can jump from one energy level to another higher level on the absorption of energy and one level to another lower orbit with the emission of energy.
3. The angular momentum of an electron moving in an orbit or energy level is an integral multiple of h/2π.

$\therefore&space;mvr=\frac{nh}{2\pi&space;}$

#### Question Set

1

1 / 9

What is the radius of the second orbit hydrogen atom if the radius of the first orbit of hydrogen atom 0.529 Å

2 / 9

The lowest wavelength of the Lyman series of the hydrogen atom is x. What is the highest wavelength of the Paschen series of the helium ion?

3 / 9

What is the wavelength of the Hɑ line of the Balmer series of the hydrogen atom?

4 / 9

The energy of an electron in the first energy level of the hydrogen atom = -13.6 eV. Calculate the energy of an electron in the excited level of helium ion

5 / 9

Find out the number of unpaired electrons of an ion M+x(Z of M = 25) with the magnetic moment √15 B

6 / 9

How many possible orbitals are there when principal quantum number = 4?

7 / 9

What are the four quantum numbers of the 19th electron of chromium?

8 / 9

How many electrons in an atom can have principal quantum number four and azimuthal quantum number one?

9 / 9

What are the four quantum numbers for the valence shell electron of rubidium atom

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