E-StoreImportant Chemical Terms - 2 ( Atomic Structure)
9 May 2007 18:39:20 IST
Important Chemical Terms - 2 ( Atomic Structure)
Important Chemical Terms - 2
ATOMIC STRUCTURE
· HUND?S RULE: when several orbital of the same type are available, the electrons 1st fill at the orbitals of same energy singly with parallel spins b4 pairing in any orbital takes place.
· INFRARED RADIATION: electromagnetic radiations possessing wavelength b/w those of visible light nd those of radio waves, i.e;frm approximately 10-4to 7x10-7 m
· ISOTOPES: atoms having the same nuclear charge, but different numbers of neutrons in their nuclei.
· MAGNETIC QUANTUM NO: denotes the orbital an electron occupies within a sub shell.
· MASS NO: the sum of no of protons nd neutrons in the nucleus.
· MOLECULAR ORBIT: a polycentric region in space associated with two or more atoms in a molecule.
· NEUTRON: uncharged sub atomic particle having a mass of 1 amu
· NUCLEUS: the central +vely charged core of an atom tht contains practically all the mass.
· ORBITS: another name for the principle energy levels occupied by electrons in atoms.
· ORBITAL: region in space around the nucleus whr the probability of finding an electron is geatest. each orbital can hold a maxi. Of 2 electrons
· ORBITAL QUANTUM NO: same as azimuthal quantum no:
· PAULI EXCLUSION PRINCIPLE: as azimuthal quantum no:
· PARAMAGNETIC: the atom of a paramagnetic substance possesses permanent magnetic moment due to unbalanced electron spin.
· PHOTONS: light quanta (hv)
· PHOTOELECTRIC EFFECT: the phenomenon in which certain metal surfaces such as cesium, sodium,?,emit electrons, when electromagnetic radiations of sufficient energy are allowed to fall on them.
· PRINCIPLE QUANTUM NO: the no: used to designate the principle energy levels tht an electron may occupy I a n atom. it determines the energy level.
· PROBABILITY DISTRIBUTIONS OF ELECTRONS: the probability tht an electron with an atom will be at a certain point in space at a given time; determined by the magnitude of the square of the wave function.
· QUANTIZED: a quantity is said to be quantized, if in accordance with quantum mechanics, it can only have certain discrete values. Such a quantity cannot vary continuously, differences in value separated by jumps.
· QUANTUM: According to the quantum mechanics, energy exists in discrete units, only whole no: of which can exist. Each unit is called a quantum.
· QUANTUM MECHANICS: According to it, energy is quantized,i.e; emitted or absorbed in discrete units, the magnitude of which is given by the product of the frequency nd Planck?s constant.
· QUANTUM NUMBERS: An electron within an atom is specified by set of four numbers, called quantum number.
1) The principle quantum no: (n) defines the shell in which the electron occurs.
2) The azimuthal quantum no: (i) defines the shape of the orbit nd energy sub level.
3) The magnetic orbital quantum no: (m) determines the orientation of the orbit, with reference to a fixed direction
4) The spin quantum no: (s) distinguishes b/w the clockwise nd anticlockwise spin of an electron. this no: is either +/- ½
· RYDBERG?S CONSTANT: A constant relating to those atomic spectra which are similar to the hydrogen atom spectrum. for hydrogen, Rydberg constant is 109.737 cm-1
· SPECTRAGRAPH: An instrument by which spectra may be photographed.
· SPECTRASCOPE: An instrument for spectrographic analysis or the observation of spectra.
· SPECTRUM: The result obtained when electromagnetic radiations are resolved into their constituent wavelengths or frequencies.
· THRESHOLD FREQUENCY: light incident on a metal will give rise to the emission of electrons only if the frequency of the light is greater than a certain threshold value, which is characteristics of the metal used.
· VOLT: A potential difference which applied across the ends of conductor having resistance of 1 ohm, causes a current of 1 ampere to flow.
· WAVE FUNCTION: in wave mechanics orbital electron is treated as three dimensional stationary wave system represented by a wave function the magnitude of which represents by the variation of amplitude of the wave system at various points around the nucleus.
· WAVE LENGTH: the distance b/w consecutive crests. it is equal to the velocity of the wave motion divided by its frequency.
· WAVE MECHANICS: According to it every particle is considered to be associated with a kind of periodic wave.
· WAVE MOTION: The propagation of a periodic disturbance carrying energy.
· WAVE NO: no of waves in unit length. reciprocal of wavelengths.
· X ? RAYS : Electromagnetic radiations of short wavelength of range 5x10 -7 cm to 6x 10-10cm.
· ZEEMAN EFFECT: When a substance, which emits a line spectrum, is placed in a strong magnetic field, the single lines are split up into group of closely spaced lines
Jyothi Susan George
Comments (5)
mimooo jj
Cool goIITian
Joined: 22 Feb 2007 22:31:17 IST
Posts: 52
9 May 2007 18:46:31 IST
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nice.....
19 Jul 2007 18:16:21 IST
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really fantastic please also give terms 4rm states of matter
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