CH3 Bonding Flashcards
What is ionic bonding
Strong electrostatic forces of attraction between oppositely charged ions held in a lattice
Example of ionically bonded substance
NaCl - Sodium chloride
How high are ionically bonded substances BP and MP - why
High - Takes lots of energy to break strong electrostatic forces of attraction between oppositely charged ions
Do ionic compounds conduct electricity - why
Yes - when molten or in solution as the ions are free to move and carry charge
What is simple molecular covalent bonding
Strong covalent bonds between atoms, weak van der Waals forces of attraction between molecules
Are there any lone electrons in simple covalent bonding
No - they are all involved in bonding
Can simple molecular molecules conduct electricity - why
No - all electrons used in bonding and arent free to move
Do simple molecular substances have high or low MP and BP - why
Low - weak van der Waals forces of attraction between molecules that dont take much energy to overcome
Descrive macromolecular covalent bonding
Lattice of many atoms held together by strong covalent bonds
Do macromolecular covalently bonded substances have high or low MP and BP - why
High - takes a lot of energy to overcome many strong covalent bonds
Do substances with macromolecular covalent bonds conduct electricity
Most dont as all electrons are used in bonding
Describe structure of diamond
3D tetrahedral structure of C atoms, with each C atom bonded to 4 others
Describe structure of graphite
Macromolecular covalent - each C atom only bonded to 3 other C atoms
Weak van der Waals forces between layers so layers can slide over each other
Conducts electricity due to 1 delocalised electron from each C atom
Describe metallic bonding
Lattice of positive metal ions strongly attracted to a sea of delocalised electrons
Malleable as layers can slide over each other
Do metallic compounds have high or low BP and MP - why
High - strong forces of attraction between positive metal ions and negatively charged sea of delocalised electrons
Do metallic compounds conduct electricity - why
Yes - delocalised electrons can move throughout the metal to carry charge
How does strength of metallic bonds change across periodic table - why
Increases - higher MP and BP
Stronger charge on metal ions
More delocalised electrons per ion
Stronger force of attraction
Define electronegativity
The ability of an atom to attract the pair of electrons in a covalent bond
What affects electronegativity
Nuclear charge
Atomic radius
Electron shielding
Most electronegative element
Fluorine - largest nuclear charge for its electron shielding, small atomic radius
How do you get non-polar bonds
Both bonding elements have the same electronegativities
When do you get a polar bond
Bonding atoms have different electronegativities
Strongest type of inter-molecular force
Hydrogen bonding
Weakest type of inter-molecular force
van der Waals forces
Describe van der Waals’ forces of attraction
Temporary dipoles are created by the random movement of electrons
Induces dipole in neighbouring molecule
Are van der Waals forces greater in smaller or larger molecules
Larger - more electrons present
Describe permanent dipole-dipole attraction
Some molecules with polar bonds have permanent dipoles
Forces of attraction between those dipoles and those of neighbouring molecules
Why is ice less dense than liquid water
Liquid - hydrogen bonds constantly break and reform as molecules move about
Ice - Hydrogen bonds hold molecules in fixed position making them further apart from each other than in liquid water
Dative covalent bond
Formed when an electron deficient atom/ion accepts a lone pair of electrons from another atom/ion with a free lone pair of electrons
What does shape of molecules depend on
Number of electrons in the valence shell of the central atom
Number of these electrons which are in bonded or lone pairs
What does the Electron Pair Repulsion Theory state
Electron pairs will take up positions as far away from each other as possible, minimise the repulsive forces between them
Which experience the most repulsion;
Lone pair - Lone pair
Lone pair - Bonded pair
Bonded pair - Bonded pair
LP - LP = strongest repulsion
LP - BP = middlle repulsion
BP - BP = weakest repulsion
Shape and bond angle of a shape with 2 bonded pairs and 0 lone pairs
Linear
180 degrees
Shape and bond angle of shape with 3 bonding pairs and 0 lone pairs
Trigonal planar
120 degrees
Shape and bond angle of shape with 4 bonded pairs and 0 lone pairs
Tetrahedral
109.5 degrees
Shape and bond angle in a shape with 5 bonded pairs and 0 lone pairs
Trigonal bipyramid
90 and 120 degrees
Shape and bond angles of shape with 6 bonded pairs and 0 lone pairs
Octohedral
90 degrees
