Bonding ( AS ) Flashcards
What is ionic bonding?
Strong electrostatic force of attraction oppositely charged ions held in a lattice
Give an example of ionically bonded substance
NaCl(sodium chloride-salt)
Do ionically bonded substances have a high melting and boiling point?
High - it takes a lot of energy to break the strong electrostatic forces of attraction between opposite charged ions
Can ionic compounds conduct electricity?
Yes, when molten or aqueous as the ions are free to move and carry charge(don’t when in solid state)
What is simple molecular covalent bonding?
Strong covalent bonds between atoms, weak van der waals forces between molecule
Are there any lone pair electrons in simple covalent bonding?
No-all involved in bonding
Can simple molecular covalent molecules conduct electricity?
No-all electrons are used in bonding and aren’t free to move
Do simple molecular substances have a high melting and boiling point?
Low-weak van der waals forces between molecules that don’t take much energy to overcome
Describe macromolecular covalent bonding
Lattice of many atoms held together by strong covalent bonds
Do substances with macromolecular covalent binds have high melting and boiling points?
High, as it takes a lot of energy to overcome many strong covalent bonds
Do substances with macromolecular covalent bonds conduct electricity?
Most don’t, as all electrons are used in bonding
What’s metallic bonding?
Lattice of positive metal ions strongly attracted to a sea of delocalised electrons
Do metallic compounds have a high melting and boiling point?
High as strong forces of attraction between positive metal ions and negatively charged sea of delocalised electrons
Do metallic compounds conduct electricity?
Yes, as delocalised electrons can move throughout the metal to carry charge
How does the strength of metallic bonds change across the perodic table?
Increases—>higher melting and boiling point, higher charge on metal ions, more delocalised electrons per ion, stronger forces of attraction between them
Define electronegativity
The ability of an atom to attract a shared pair of electrons in a covalent bond
What affects electronegativity?
Nuclear charge
Atomic radius
Electron shielding
What is the most electronegative element?
Fluorine(4.0 on Paulings scale)
Largest nuclear charge for its electron shielding, small atomic radius
How do you get a non-polar bond?
Both bonding elements have the same electronegativities
When do you get a polar bond?
Bonding atoms have different electronegativities
What is the strongest type of intermolecular force?
Hydrogen bonding
What is the weakest type of intermolecular force?
Van der waal forces
Describe van der waals forces of attraction
●Temporary dipoles are created by the random movement of electrons
●induces dipole in neighbouring molecule
●temporary induced dipole-dipole attraction aka van der waals forces
Are van der waals forces greater in smaller or larger molecules?
Larger-more electrons
Describe permanent dipole-dipole attraction
Some molecules with polar bonds have permanent dipoles—> forces of attraction between those dipoles and those neighbouring molecules
What conditions are needed for hydrogen bonding to occur?
O-H,N-H, or F-H bond, lone pair of electrons on O,F,N because O,N,and F are highly electronegative, H nucleas is left exposed.
Strong force of attraction between H nucleas and lone pair of electrons on O,N,F
Why is ice less dense than liquid water?
In liquid water, hydrogen bonds constantly break and reform as molecules move about.
In ice, the hydrogen bonds hold the molecules in fixed positions; this makes them slightly further apart than in liquid water
What is dative/ coordinating covalent bond? When is it formed?
A type of covalent bond where both the electrons in the shared pair come from the same atom
What does the shape of molecule depend on?
●Number of electrons in the valence shell of the central atom
●number of these electrons, which are 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 to minimise the repulsive forces between them
Which experience the most repulsion?
LP-LP repulsion strongest
LP-BP repulsion middle
BP-BP repulsion weakest
What is the shape, diagram, and bond angle in a shape with 2 bonded pairs and 0 lone pairs?
Linear
180°
What is the shape, diagram, and bond angle in a shape with 3 bonding pairs and 0 lone pairs?
Trigonal planar
120°
What is the shape, diagram, and bond angle in a shape with 4 bonding pairs and 0 lone pairs?
Tetrahedral
109.5°
What is the shape, diagram, and bond angle in a shape with 5 bonded pairs and 0 lone pairs?
Trigonal Bipyramidal
90° and 120°
What is the shape, diagram, and bond angle in a shape with 6 bonded pairs and 0 lone pairs?
Octahedral
90°
