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__History of the Atom__ Orginal idea Ancient Greece (400 B.C) Democritus and Leucippus-Greek philosphers Aristole-famous philospher 4 elemenets= fire, water, air, earth John Dalton-Teacher ( late 1700) summarized results of his experiments and those of others __Dalton's Atomic Theory__ 1.) All matter is made of tiny indivisible particles called atoms 2.) Atoms of the same element are identical, those of diffrent elements are diffents 3.)Atoms of diffrent combine in whole number ratios to form ccompounds 4.) Chemical reactions involve the rearrangement of atoms. No new atoms are created or destroyed __ Parts of the Atom __ made a piece of equipment called a carthode ray tube. It is a vacuum tube which means all the air has been pumped out
 * J.J. Thompson-English Physicist (1897)



__ Rutherfords Model of the Atom  __
 * Proton- postively charged pieces that are 1840 times heavier than the electron- by E. Goldstein
 * Neutron- no charge but the same mass as a proton- by J. Chadwick

__ Electromagnetic Radiation __
 * microwave O
 * infra red R
 * ultra violet
 * radio waves Y
 * x-rays I
 * visible light
 * gamma rays



Wavelength

Wavelength is large - energy is small Wavelength is small - energy is large

**Frequency** --> how many times/a period of time

**Spectroscopes:** instruments used to measure the behaviour of radiation __Bohr Model of Atom__




 * Ground State Electrons:** electrons in the lowest energy level

__Drawback of Rutherford Model of Atoms__ 1) The atom is not stable due to continuous emission of radiation(EMR) 2) Cannot explain the line spectra of Hydrogen like atoms

**Quantised:** Fixed Energy. Every orbit(shell or energy level) has a fixed value for its energy. (It will not change). Energy will be absorbed or emitted in discrete quantities.

**RAM:** Relative Atomic Mass **Unified Atomic Mass:** a unit of mass for atoms; 1/12 of the mass of carbon- 12 atom( theortical definition)14= 1/12 of C-12 ( Isotope of C)

__Quantum Mechanical Model of an Atom__ **Orbital:** It is a 3 dimensional space around the nucleus where there is a very high probability of locating the electrons.


 * Hesembergs Uncertanity Principle:** It is impossible to determine both the position and momentum of an electron with 100% accuracy.


 * Quantum Numbers:** These are a set of 4 integers necessary to specify the energy, position, shape, size and orientation of orbital's to which electrons belong.

**Principle Quantum Number "n":** It specifies the location and //energy// of an electron, It is a measure of the effective volume or //size// of the electron cloud denoted by "n" and can have values 1,2,3,4..........


 * Azimuthal Quantum Number"l":** It determines the shape of the orbital. It takes integral values from 0 (n-1) where "n" id the principle quantum number. When "l" = 0,1,2, the shapes of the orbital's are "s" Spherically symmetrical, "p" dumbbell, and "d" double dumbbell


 * l || 0 || 1 || 2 || 3 || 4 ||
 * Orbital || s || p || d || f || g ||
 * Shape || Sphercally Symmetrical || Dumbell || Double Dumbell || || ||


 * Magnetic Moment Quantum Number 'm':** (2l+1) values It gives the orientation of the orbital's in space. It takes integral values ranging from -l......0.......+l or 's' orbital has got one orientation, 'p' orbital has got 3 orientations, 'd' orbital has got '5' orientatios and 'f' orbital has got 7 orientations.


 * Spin Quantum Number 's':** it indicates the direction in which the electron spins on its own axis or the magnetic property that is associated with it. This value is quantised the two values htat are permitted are +1/2 and -1/2 where g=gyro magnetic constant.


 * ORBIT || ORBITAL ||
 * a well defined circular path around the nucleus in which the electron revolves || a region in 3D space around the nucleus where there is a very high probability of locating the electron ||
 * circular in shape || 's', 'p' and 'd' orbital's are spherical, dumbell and double dumbell in shape respectively ||
 * represents the movement of an electron around the nucleus on one plane || represents the movement of an electron around the nucleus in a 3D space ||
 * states with certainty the momentum and position of an electron. Violates the Heisenberg's uncertainty principle || a consequence of Heisenberg's uncertainty priciple. i.e. The posision and momentum cannot be known with certainty ||
 * the maximum number of electrons in an orbital is 2n2 || the maximum number of electrons in an orbital is 2 ||


 * Degenerate Orbital's:** The orbital's of the same sub shell having equal energy are called degenerate orbital's. e.g. Px, Py, Pz orbital's. The 5 'd' orbital's are degerate but can lose their degeneracy under the infulence of and external electrical or magnetic field.


 * Nod****al Plane:** The plane passing through the nucleus on which the probability of finding the electron is almost zero.


 * Type of Information || Principal Quantum Number 'n' || Azimuthal Quantum Number 'l' || Magnetic Moment Quantum Number 'm' || Spin Quantum Number 's' ||
 * Why is it required? || To explain the main lines of spectra || To explain the fine structure of line spectra || To explain the splitting of lines in the magnetic field || To explain the magnetic properties of substances. ||




 * Electron Configuration of atoms:** rules governing the filling up of electrons in the different orbital's of an atom


 * Orbital's:** arranged in the increasing order of energy which is based on Aufbau order and can be verified using the (n+1) rule.

1s,2s,3s,3p,4s,3d,4p,5s,4d,5p,6s,4f,5d,6p,7s or 1s2,2s2,3s2,3p6,4s2,3d10,4p6,5s2,4d10,5p6,6s2,4f14,5d10,6p6,7s2
 * Aufbau Order:** the number of electrons that can be accomodated in an 'orbit' is 2n2 where n is the principal quantum number.


 * PEP or Pauli's Exclusion Principle:** No two electrons in an atom can have all the four quantum numbers alike or an orbital can accommodate a maximum of 2 electrons in an atom.

*Exceptional Electronic Configuration* Cu, Cr, Mo, Ag, W and Au have got exceptional electronic configuration. Half filled 'd' orbital configurations are preferred because
 * Hund's Rule of Maximum Multiplicity:** Electrons pairing will not take place in orbital's of the same energy (same sub shell) until each orbital is singly filled.
 * there is a extra stability because of the symmetrical distribution of the electrons in the orbitals.
 * the exchange energy is high for Cr, Mo and W
 * exchange energy can be calculated using the following equation. where 'n' is the number of electons having parallel spins. In the equation given below 'n' stands for the number of unpaired electrons in the 'd' orbital.


 * SATP:** Standard Ambient Temperature and Pressure. Corresponds to 25 c


 * STP:** Standard Temperature and Pressure used to measure gas density and volume.


 * Isoelectronic:** refers to a group of atoms ot ions having the same number of electrons. For excample, F-, Ne, Na+, are all isoelectronic.

__**Ionisation Energy:**__

The energy required to remove an elctron fron the neutral gaseous atom.

Na+ IE > Na+ e- 1s2,2s2,2p6,3s1+IE 1s2 ,2s2,2p6 + e- (less stable ) ( more stable)

__**Electron Affinity**__

It is the energy released when an electron's added to a neutral gaseous atom(usually non-metals)

F+ e>F-+ EA

Moving from left to right, the elesctrons are added to the same energy level and there is an increase in nuclear charge. Therefore the size of the atom decreases.


 * __Electronegativity:__**

It is defined as the tendency of an atom to attract a shared pair of electrons.

__**Forces of Attraction**__

INTRAmolecular forces of attraction (inside the molecule) 1.) Covalent Bonds 2.) Ionic Bonds 3.) Co-ordinate Covalent 4.) Metallic Bond

H2 H-H Cl2 Cl- Cl H20 H-O-H

INTERmolecular forces of attraction (between the molecule)

1.) Hydrogen Bonds (Strongest Force) 2.) Dipole-Dipole Attraction ( Vanderwaals Force) 3.) London's Dispersion ( Weakest Force)


 * Valence Electrons-** The s and p electrons in the outer energy level. It is hte highest occupied eneergy level.


 * Core electrons-** Those in the energy levels below

__**Electron Configuration for Cations**__

Metals lose elctrons to attain noble gas configuration They make positive ions ( cations)