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Dubai

A Level Chemistry Edxcel Bonding

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Published in: Chemistry
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Here we will discuss about the ionic bond , covalent bond , cordinate covalent bond and its properties

Babar M / Dubai

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Qualification: Master of science in chemistry(MSC CHEMISTRY), Bachelors of science in Chemistry, ( BSC biology) Biology , A levels , o levels

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  1. EARN CHEMISTRY WITH BABABR EDXC A LEVEL CHEMI TRY BONDI G TOPIC 3
  2. ELECTRONEGATAVAVY ANO Electronegativity: the power of an atom to attract electrons to itself The electronegativity depends on: • The radius of atom (atomic size) inversely oc oc electronegativity • Nuclear attraction directly cc cc electronegativity Electronegativity increases across a period because of atomic radius J and nuclear attraction t, so polarity t Electronegativity decreases down a group because of atomic radius t and nuclear attraction J, so polarity J Dipole Moment: slight charges on atoms in a covalent bond due to differences in electronegativity The difference between the electronegativity of two atoms in a compound determines the overall dipole moment and overall polarity of the compound. A large difference in electronegativity will make the bond more polar (more ionic in nature), but a small difference in electronegativity will make the bond less polar (more covalent in nature)
  3. An ionic bond is the electrostatic attraction between oppositely charged ions. Structure: giant ionic lattice, crystalline solids Have high melting and boiling points Coordination Number: number of oppositely charged ions that surround a particular ion in an ionic solid E.g: NaCl, MgC12 Cl
  4. 00T ANO CROSS OAAGRAWS For anions, electrons are added to the atom (e.g. Chlorine forms Chloride Cl- ions. For cations, electrons are removed from the atom (e.g. Sodium forms Na• ions. Atoms form the same number of bonds as the number of electrons required to be added/removedfor maximum stability. (e.g.: Chlorine will form 1 bond, Sodium will form 1 bond, but Calcium Ca2• will form 2 bonds The central atom may expand its octet to form more bonds if necessary (e.g, Sg In ionic compounds, electrons are shown to be completely transferred to each of the ions in the compound.
  5. Strong electrostatic forces of attraction between metal cations and delocalized mobile electrons Structure: lattice of +ve ions surrounded by --mobile e-s Strength of metallic bond increases with: • Increasing positive charge on the ions in the lattice • Decreasing size of metal ions in the lattice Metallic Bond Examples + bo@ö Aluminum METALIC BOND
  6. COVALENT BONOÅNG Covalent Bond: the bond formed by the sharing of pairs of electrons between the nuclei of two atoms. Bonding Electrons: e-s involved in bond formation Non-bonding electrons or lone pair: pair of valence e-s that are not involved in bond formation Covalent compounds are made of molecules which are held together by weak intermolecular forces Elements in period 3 can expand their octet, including the compounds sulfur dioxide, S02, phosphorus pentachloride, PC15, and sulfur hexafluoride, SF6. They have low melting and boiling points.
  7. COOROANATE (OATAVE COVALENT) A coordinate bond is a covalent bond where both electrons in the bond come from the same atom Conditions: An atom should have a lone pair of electrons An atom should be in need of a pair of electrons Donor: the atom that supplies the pair of electrons Acceptor: the atom that accepts the pair of electrons one pair of electrons Coordinate bond is represented by H X + an drawn from the atom donating to towards the atom accepting Formation of Ammonium ion NH4+NH4+: ammona molecu e hydrogen coordinate bond ammonium
  8. ORBATAL OVERLAP For a covalent bond to form, atomic orbitals containing unpaired valence electrons must overlap each other S - S (Sigma E) S- P (Sigma E) P- P (Sigma E) Sigma bond has greater overlap . Pi bond cannot exist without a Sigma bond. Note: Elements in Period 3 can expand their octet by making use of the energetically accessible but lower lying d-subshell for bonding. This means that some elements of period 3 can bond with more than 4 electrons at once. (e.g: Sulfur, Phosphorus etc)
  9. S#APES OF 1 goo E.g. C02 3 pairs 4 pairs 3 I pair 2 2 pair 5 pairs 900 and 12cP E.g. PFs
  10. Mix atomic orbitals like s and p to form new hybrid orbitals like sp2sp2, sp3sp3, and spsp. The resultant orbital has different energy levels, shapes, and properties. spsp Hybridisation When 1 s orbital combines with 1 p orbital. They form linear molecules with 18001800 angles, e.g. C02C02 and all hydrocarbons containing 2 bonds like C2H2C2H2 (Carbon-Carbon triple bond). Has an equal amount of s and p orbital properties.
  11. SP2 When 1 s orbital combines with 2 p orbital. They form linear molecules with 12001200 angles, e.g. BH3BH3 and all hydrocarbons containing 3 bonds like C2H4C2H4 ( ). Has twice the property of p orbital properties than s orbital.
  12. When 1 s orbital combines with 3 p orbital. They form linear molecules with 109.250109.250 angles, e.g. SiC14SiC14, and all hydrocarbons containing 4 bonds like C2H4C2H4 ( C-CC-C ). Has three times the property of p orbital properties than s orbital.
  13. Bond Energy: the energy needed to break one mole of a given bond in one mole of gaseous molecules Bond Length: distance between the centres of two nuclei of two adjacent atoms Double bonds are shorter than single bonds because double bonds have a greater negative charge density between the two atomic nuclei hence greater attraction The bond length depends on the radii of the two bonded atoms; the larger the radius, longer the bond length The strength of the bond depends on the length of the bond
  14. The strongest type of intermolecular force in covalent bonds For hydrogen bonding to occur, we need: • A molecule having a H atom bonded to F, O or N • Molecule having F, O or N atom with lone pair of e-s Water Ammonia bond
  15. POLAR ANO NON-POLAR Polar Covalent Bonds Bonds with slight ionic character The bond formed with atoms of different electronegativity Bonding e-s attracted more towards atom with greater electronegativity unequal sharing of electrons :.:. molecule develops slight charges = Polar Molecule Polar molecules have dipoles, electric charges of equal magnitude and opposite sign The greater the difference in electronegativity of the two bonded atoms, the greater is the ionic character Non-Polar Covalent Bonds The bond formed between: • Identical Atoms: the electronegativity of both atoms is the same so a pair of electrons shared equally • Symmetrical Polyatomic Molecules: dipoles of bond expert equal & opposite effects, hence cancel charge Non-polar molecules have no overall charge
  16. FORCES o Intermolecular Forces: weak forces present between two covalent molecules @ Induced Dipole (Van Der Waals' Forces) Very weak forces present between non-polar molecules Due to constant motion of e-s, at an instant, a non-polar molecule develops poles due to distortion of electron density giving rise to instantaneous dipole, which can induce a dipole in the adjacent molecules Van der Waals forces increase with: • increasing the number of contact points between molecules; point where molecules come close together • increasing number of electrons (+ protons) in molecule Permanent Dipole-Dipole Forces Weak forces present between polar molecules Molecules are always attracted to charged rods, whether +ve or -ve because molecules have +ve and -ve charges

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