Chemical energetics (Section 2 of 2)

What does Lattice enthalpy depend upon?Charge of the ions: As the charge increases the lattice enthalpy becomes more exothermic For Example: Lattice enthalpies of  (Mg has a 2+ charge while Li has a 1+ charge) MgO.......-1050 KJ/mol LiO.........- 3923 KJ/mol Size of the ions: the lattice enthalpy becomes less exothermic as the size of the ion decreases, because as the size increases the the attraction between the two oppositely charged ions...

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Chemical energetics (Section 1 of 2)

The Born Haber CycleWhat is the Born Haber Cycle?The born Haber cycle can be used to determine lattice enthalpy of a compound. In the born Haber cycle every step from the elements to the ionic compound can be measured experimentally except the lattice enthalpy which therefore can be calculated using the Hess's law What is Lattice enthalpy?Lattice enhalpy is the energy change that occurs when 1 mole of an ionic compound is formed from its gaseous...

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Chemical Bonding (Section 2 of 2)

Contents of this page Intermolecular forces of attraction Hydrogen Bonding Vander Waals Forces Temporary Dipole induced dipole Forces Dipole Dipole forces of attraction ======================================== Van der Waals Forces and Hydrogen BondingHydrogen Bonding (The strongest Force) What is Hydrogen Bonding? In hydrogen bonds, the positively charged hydrogen end of one molecule is attracted to the negatively charged end of another...

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States of Matter

The Kinetic Theory of Matter i      All matter is composed of small particles. ii     The particles of matter are in constant motion. iii     All collisions between the particles of matter are perfectly elastic Particle motion: atoms move in a straight line between collisions. The Solid State Gases: The Kinetic Theory Two of the basic assumptions of this theory are: Actual...

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Basic Calculations in A-level Chemistry

The Mole Balancing chemical Equations Molecular and empirical formul...

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Bond Angles

Valence-shell electron-pair repulsion (VSEPR) theory Assumes that each atom in a molecule will be positioned so that there is minimal repulsion between the valence electrons of that atom. In simple molecules in which there are no nonbonding electrons, there are five basic shapes: LINEAR - Bond angle = 180 All diatomic molecules are linear. Molecules with two atoms around a central atom such as BF2 are...

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Chemical Bonding (Section 1 of 2)

Contents of this Page: The Bond Energy Factors affecting the Bond energy The Four Main Types of Bonding Ionic Bonding Covalent Bonding Dative Covalent Bonding Metallic Bonding Section 2 ============================================ The Bond Energy The energy required to break one mole of covalent bonds in gaseous state is called bond energy For Example H=H Bond Energy = +436 KJ/mol I-I Bond Energy = +151 KJ/mol Factors affecting Bond Energy Number of Bonds: Triple bonds are stronger than double bonds and double bonds are stronger than single bonds. Bond Length: Bond length is the distance between two nuclei of covalently bonded atoms as the...

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Atoms molecules and stoichiometry

Before proceeding with this section please make sure you have seen all the lectures on the Basic Calculations in A-level Chemistry page Mass number and atomic number Atomic Number (Z)      Number of protonsin the nucleus of an atom Mass Number (A)       Sum of the protons and neutronsin the nucleus What is the avogadro's constant? The Avogadro Constant is a constant number used to refer to...

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Atomic Orbitals and electronic configurations

Atomic OrbitalsAn orbital subdivision of a subshell. A region of space around the nucleus of an atom where there is maximum probability of finding an electron The following video explains the above concept extremely well: Electronic configurationsNot more than two electrons to be placed in one orbital If two or more electrons are to be placed in one orbital they must be placed with opposite spin to minimize repulsio...

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Ionization Energy

Ionization Energy:Energy required to remove one mole of electrons from one mole of gaseous atoms Factors affecting Ionization Energy Atomic size As atomic size increases the ionization energy increases Shielding affect Ionization energy decreases as shielding affect increases Trend of ionization energy in the periodic table:Ionization energy decreases down the group As we move down the group shell size increases and so the distance from the nucleus...

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