Trends in properties of group 14 elements:
Trans Web Educational Services Pvt. It may be noted that ionic bond is not a true bond as there is no proper overlap of orbitals.
Criteria for Ionic Bond: One of the species must have electrons in excess of octet while the other should be deficit of octet. Does this mean that all substance having surplus electron and species having deficient electron would form ionic bond?
The answer is obviously no. Now you should ask why?
The reasoning is that in an ionic bond one of the species is cation and the other is anion. To form a cation from a neutral atom energy must be supplied to remove the electron and that energy is called ionization energy.
Now it is obvious that lower the ionization energy of the element the easier it is to remove the electron. To form the anion, an electron adds up to a neutral atom and in this process energy is released. This process is called electron affinity. So for an ionic bond one of the species must have low ionization energy and the other should have high electron affinity.
Low ionization energy is mainly exhibited by the alkali and alkaline earth metals and high electron affinity by the halogen and chalcogens. Therefore predominant in the field of ionic bonding. A The energy released from this step is called electron affinity E. Now for stable ionic bonding the total energy released should be more than the energy required.
From the above discussion we can develop the factors which favour formation of ionic bond and also determine its strength. These factors have been discussed below: In the formation of ionic bond a metal atom loses electron to form cation.
Lesser the value of ionization energy, greater is the tendency of the atom to form cation. For example, alkali metals form cations quite easily because of the low values of ionization energies. Electron affinity is the energy released when gaseous atom accepts electron to form a negative ion.
Thus, the value of electron affinity gives the tendency of an atom to form anion. Now greater the value of electron affinity more is the tendency of an atom to form anion. For example, halogens having highest electron affinities within their respective periods to form ionic compounds with metals very easily.
Once the gaseous ions are formed, the ions of opposite charges come close together and pack up three dimensionally in a definite geometric pattern to form ionic crystal. Since the packing of ions of opposite charges takes place as a result of attractive force between them, the process is accompanied with the release of energy referred to as lattice energy.
Lattice energy may be defined as the amount of energy released when one mole of ionic solid is formed by the close packing of gaseous ion.
In short, the conditions for the stable ionic bonding are:The process for predicting the shape of a molecule is summarized below: Step 1: Draw the Lewis formula for the molecule.5° for a tetrahedral arrangement of electron pairs.
the hydrogen fluoride molecule has one bonding pair and three lone pairs of electrons. “angular. boron cannot form an octet in a simple molecule where one boron is the. The Lewis structure for Helium is He with two dots next to each other, above the He symbol.
The dots must be drawn next to each other, they represent the two electrons found i n the 1s-orbital. (b) Describe the (supercage) polyhedron at the centre of the Zeolite A structure in Fig.6 cm3) = 4 strongly acidic OH groups per molecule Write balanced chemical equations for the reactions of K2CO3 with HCl(aq) and of Na4SiO4 with aqueous acid?
For each of these molecules, draw the best possible Lewis structure. Using that Lewis structure, predict the electron-pair geometry, the molecular geometry, the hybridization of the central atom, and whether the molecule is polar.
Lewis symbols for atoms are combined to write Lewis structures for compounds or molecules with bonds between atoms. Writing Lewis Symbols for Atoms The Lewis symbol for an atom depicts its valence electrons as dots around the symbol for the element. Write a chemical equation showing the reaction between ammonia and boron trifluoride, BF3, in a Lewis acid-base reaction.
Show how the covalent bond forms. Write chemical formulas representing each of the six types of compounds listed below.