19-07-2014, 12:51 PM
Atomic Structure
[attachment=66003]
Discovery of neuton
Neutrons were discovered by James Chadwick by bombarding a thin sheet of beryllium by a - particles. They are electrically neutral particles having a
mass slightly greater than that of the protons
Thomson Model
This model proposed that atom is considered as a uniform positively charged sphere and electrons are embedded in it. An important feature of Thomson model of an atom was that mass of atom is considered to be evenly spread over the atom. Thomson model of atom is also called as Plum pudding, raisin pudding or watermelon model.
Spectrum
When a white light is passed through a prism, it splits into a series of
coloured bands known as spectrum.
Spectrum is of two types: continuous and line spectrum
a. The spectrum which consists of all the wavelengths is called continuous
spectrum.
b. A spectrum in which only specific wavelengths are present is known as a
line spectrum. It has bright lines with dark spaces between them.
Electromagnetic spectrum is a continuous spectrum. It consists of a range of electromagnetic radiations arranged in the order of increasing wavelengths or decreasing frequencies. It extends from radio waves to gamma rays.
Emission spectrum: A substance absorbs energy and moves to a higher
energy state. The atoms, molecules or ions that have absorbed radiation
are said to be excited. Since the higher energy state is unstable they
return to the more stable energy state by emitting the absorbed radiation
in various regions of electromagnetic spectrum. The spectrum of radiation
emitted by a substance that has absorbed energy is called an emission
spectrum.
Absorption spectrum is the spectrum obtained when radiation is passed
through a sample of material. The sample absorbs radiation of certain
wavelengths. The wavelengths which are absorbed are missing and come
as dark lines.
Electronic configuration
The electronic configuration of different atoms can be represented in two ways
a. sapbdc .. notation: In the first notation, the subshell is represented by the respective letter symbol and the number of electrons present in the subshell is depicted, as the super script, like a, b, c, ... etc. The similar subshell represented for different shells is differentiated by writing the principal quantum number before the respective subshell.
b. Orbital diagram: In the second notation, each orbital of the subshell is represented by a box and the electron is represented by an arrow (↑) a positive spin or an arrow (↓) a negative spin.
[attachment=66003]
Discovery of neuton
Neutrons were discovered by James Chadwick by bombarding a thin sheet of beryllium by a - particles. They are electrically neutral particles having a
mass slightly greater than that of the protons
Thomson Model
This model proposed that atom is considered as a uniform positively charged sphere and electrons are embedded in it. An important feature of Thomson model of an atom was that mass of atom is considered to be evenly spread over the atom. Thomson model of atom is also called as Plum pudding, raisin pudding or watermelon model.
Spectrum
When a white light is passed through a prism, it splits into a series of
coloured bands known as spectrum.
Spectrum is of two types: continuous and line spectrum
a. The spectrum which consists of all the wavelengths is called continuous
spectrum.
b. A spectrum in which only specific wavelengths are present is known as a
line spectrum. It has bright lines with dark spaces between them.
Electromagnetic spectrum is a continuous spectrum. It consists of a range of electromagnetic radiations arranged in the order of increasing wavelengths or decreasing frequencies. It extends from radio waves to gamma rays.
Emission spectrum: A substance absorbs energy and moves to a higher
energy state. The atoms, molecules or ions that have absorbed radiation
are said to be excited. Since the higher energy state is unstable they
return to the more stable energy state by emitting the absorbed radiation
in various regions of electromagnetic spectrum. The spectrum of radiation
emitted by a substance that has absorbed energy is called an emission
spectrum.
Absorption spectrum is the spectrum obtained when radiation is passed
through a sample of material. The sample absorbs radiation of certain
wavelengths. The wavelengths which are absorbed are missing and come
as dark lines.
Electronic configuration
The electronic configuration of different atoms can be represented in two ways
a. sapbdc .. notation: In the first notation, the subshell is represented by the respective letter symbol and the number of electrons present in the subshell is depicted, as the super script, like a, b, c, ... etc. The similar subshell represented for different shells is differentiated by writing the principal quantum number before the respective subshell.
b. Orbital diagram: In the second notation, each orbital of the subshell is represented by a box and the electron is represented by an arrow (↑) a positive spin or an arrow (↓) a negative spin.