C3. Bonding Flashcards
What effect do lone pairs have on bond angles?
Greater repulsion than bonding pairs, lone pairs have 2.5 degree effect on bond angles
What are the different types of bonding?
Ionic, Covalent, Metallic
What is ionic bonding?
Electrostatic attraction between positive and negative ions in a lattice
What substances can an ionic bond exist between?
Metal - non metal ions; hydrogen - non metal ions
What are the properties of ionic compounds?
Crystalline solids, high melting and boiling points, soluble in water, conduct electricity as molten or aq, hard and brittle
Why do ionic structure have high melting and boiling points?
Large amount of energy required to overcome large number of strong electrostatic forces between ions in lattice
Why are ionic substances soluble in water?
+ and - dipoles in water are attracted to ions and pull lattice apart, energy is required (endothermic)
Why are ionic compounds hard and brittle?
Strong electrostatic forces holding lattice together, when struck, ions with like charge align and repel
What is a covalent bond?
Shared pair of electrons which are attracted to the nuclei in each atom
What substances can a covalent bond exist between?
Non metal atoms
What is a discrete covalent bond?
Small group of atoms held by strong covalent bond and weak intermolecular forces
What is a giant covalent bond?
3D structure held together by covalent bonds
What are the general properties of covalent bond?
Low melting and boiling points, no electrical conductivity, insoluble in water
What is a dative covalent bond?
Covalent bond where both electrons come from same atom
How do you show a dative covalent bond in a diagram?
Arrow point from donating atom to receiving atom
What is metallic bonding?
Valence electrons can move from one atom to another creating a cloud of delocalized electrons. The positive metal ions are immersed in this cloud. Electrostatic interactions are responsible for the metallic bond.
Metallic bonding joins a bulk of metal atoms
What are the physical properties of metals?
High density, high melting and boiling point, electrical conductivity, thermal conductivity, malleable, ductile
Why do metals have high melting and boiling points?
Many strong electrostatic forces hold lattice together, lots of energy required to overcome
Why can metals conduct electricity?
Delocalised electrons move randomly through lattice of positive ions, potential difference connected, carrying charge
Why do metals conduct heat?
Electrons bump into ions in cooler regions to transfer energy, vibration of tightly packed metal ions
Why are metals malleable and ductile?
No rigid bonds between lattice layers, atom layers can slide
What are examples of giant covalent structures?
Diamond, Graphite, Ice, Iodine
What is an example of a giant metallic structure?
Magnesium
What is an example of a giant ionic structure?
Sodium chloride
What are the properties of iodine?
Atoms are big so many weak Van der Waals forces ; macromolecular lattice; small amount of heat energy to overcome forces; hence sublimation
What are the properties of ice?
Covalent bonds between O & H; solid state hydrogen bonding between water molecules, 3D lattice; intermolecular hydrogen bonds are weak, low energy to overcome attractive forces ; Water low melting and boiling points
What are the properties of diamond?
Hard, high melting and boiling point. each atom 4 covalent bonds, no electrical conductivity
What are the properties of graphite?
High melting and boiling point, soft flaky, layers can slide over each other due to weak Van der Waals forces, electrical conductivity, carbon bonded to 3, 1 free delocalised electron
What are the properties of magnesium?
High melting and boiling point, Electrostatic attraction between metal ions and delocalised electrons, strong giant metallic lattice
What are the properties of sodium chloride?
High melting and boiling point, electrostatic attraction between + ions and - ions, strong giant ionic lattice
What is electronegativity?
Power of an atom to attract the electron density in a covalent bond towards itself
How is electronegativity measured?
Pauling scale 0 - 4 (4 most electronegative)
What are the factors that increase electronegativity and why?
Smaller atoms, bonding electrons to nucleus ; Larger nuclear charge, greater attraction for bonding electron; Less shielding, greater attraction between nucleus and bonding electron
What are the electronegativity trends across a period?
Electronegativity increases - same shielding , decreasing atomic radius, increasing nuclear charge
What are the electronegativity trends down a group?
Electronegativity decreases - shielding and distance from nucleus increases
What is the most electronegative element?
Fluorine , Pauling scale 4.0
What is bond polarity?
Unequal sharing of electron density as result of difference in electronegativity
What are different types of intermolecular forces (ascending order) ?
Van der Waals forces, Permanent dipole-permanent dipole, hydrogen bonds
What are the properties of Van der Waals forces?
1/1000 of covalent bond,Weakest IMF, due to momentary dipoles, exist for moments, increases boiling point
How do intermolecular forces affect alkane structures?
Straight chain alkane, pack closer together, more points of contact between molecules, stronger Van der Waals forces
What are the properties of permanent dipole-permanent dipoles?
1/100th of covalent bond; polar molecules, permanent dipoles;
What are the properties of hydrogen bonding?
1/10th of covalent bond; Positive hydrogen strongly attracted to lone pairs of N O F, highly electronegative, strong permanent dipole-dipole forces
What shape and angle does 2 electron pairs create?
Linear, 180
What shape and angle does 3 electron pairs create?
Trigonal planar, 120
What shape and angle does 4 electron pairs create?
Tetrahedral, 109.5
What shape and angle does 5 electron pairs create?
Trigonal bipyramidal, 90, 120
What shape and angle does 6 electron pairs create?
Octahedral, 90
What shape and angle does 2 electron pairs and 2 lone pairs create?
Bent, 106.5
What shape and angle does 3 electron pairs and 1 lone pairs create?
Triangular pyramidal, 107
What shape and angle does 4 electron pairs and 2 lone pairs create?
Square planar, 120
