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37 Cards in this Set
- Front
- Back
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a) How are ions formed?
b) Why do they attract each other? |
a) Electrons are transferred from metals to non-metals.
b) Through electrostatic attraction as they are oppositely charged. |
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Define ionic bonding.
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A chemical bond in which an electron or electrons are transferred from one atom to another, resulting in the formation of oppositely charged ions held together in a crystal lattice by electrostatic attraction.
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What are the five properties of ionically bonded compounds?
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>Solid at room temperature
>Have giant structures, therefore high melting and boiling temperatures >Do not conduct electricity unless molten or dissolved in water (free ions) >Brittle >Dissolve in water |
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Define covalent bonding?
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A shared pair of electrons, one electron being supplied by each atom either side of bond.
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Define co-ordinate/dative covalent bonding?
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A shared pair of electrons, both electrons being supplied by one atom in the bond, and the other atom having an empty orbital.
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What are the three properties of covalently bonded molecules?
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>Low melting and boiling temperatures due to bonds only being between atoms and no attraction between atoms
>Poor conductors - no charged particle >Dissolve in organic solvents |
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How many electrons are shared in
a) a single covalent bond? b) a double covalent bond? |
a) 2
b) 4 |
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What is meant by the term electronegativity?
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The ability of an atom to attract the pair of electrons in a covalent bond towards itself.
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What three things define an atoms electronegativity?
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>Nuclear charge
>Distance between nucleus and outer shell electrons >Shielding of nuclear charge by electrons in inner shells |
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What is the nature of bonding in a metal?
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Lots of delocalised electron spread over a lattice of positive ions.
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What are the properties of metals?
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>Good conductors of electricity and heat
>Strong >Malleable >Ductile >High melting and boiling points |
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What are the three types of intermolecular force?
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>van der Waals forces - act between all atoms and molecules
>Dipole-dipole forces - act only between certain types of molecules >Hydrogen bonding - acts only between certain types of molecules |
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How do dipole-dipole forces arise?
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Dipole-dipole forces act between molecules with permanent dipoles.
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How do van der Waals forces arise?
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Caused by the changing position of the electron cloud.
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How do dipole moments arise?
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In certain molecules some of the atoms are more electronegative than others pulling the electrons towards themselves.
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What is needed for hydrogen bonding to occur?
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A hydrogen atom that is bonded to a very electronegative atom.
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What elements are electronegative enough for hydrogen bonding to occur?
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FON.
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What energy changes occur when solids melt?
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Energy is needed to weaken forces holding particles in solid state. No temperature change, heat is turned to kinetic energy.
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What energy changes occur when liquids vaporise?
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Energy is needed to break all the intermolecular forces between particles. No temperature change, thermal to kinetic.
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How are the values of enthalpies of fusion and vaporisation explained?
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The heat measured under constant pressure. The temperature depends on the average kinetic energy of particles so is related to their speed, the greater the energy the faster they go.
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What are the physical properties of macromolecular solids?
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>Covalent
>Strong bonds >High melting point |
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What are the physical properties of molecular solids in terms of their detailed structures and bonding?
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>Molecules held in regular arrays by one or more of the three types of intermolecular forces
>Covalent bonds within molecules hold atoms together but do not act between molecules >Low melting points >Weaker than covalent, ionic and metallic bonding |
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What are the three types of strong bonding?
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>Ionic - metal and non-metal
>Covalent - non-metal atoms only >Metallic - metal atoms only |
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How is electrical conductivity related to bonding?
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>Metallic - good conductor due to delocalised electrons
>Ionic - conducts only in liquid state or dissolved in water >Covalent - Does not generally conduct, (no charged particles) unless reacted to form ions. Ifffy, graphite!!! |
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What is the shape of an atom with two pairs of electrons in outer shell?
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>Linear
>180 degrees (furthest away they can get) |
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What is the shape of an atom with three pairs of electrons in outer shell?
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>120 degrees
>Flat >Trigonal planar |
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What is the shape of an atom with four pairs of electrons in outer shell?
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>Tetrahedral
>109.5 degrees >Three dimensional (sum of angle can be more than 360) |
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What is the shape of an atom with five pairs of electrons in outer shell?
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>Trigonal bipyramid
>120 degrees |
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What is the shape of an atom with six pairs of electrons in outer shell?
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>Octahedral
>90 degrees |
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What rules govern the shapes of simple molecules?
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The number of pairs of electrons on the outer shell. Each pair will repel every other pair as far away as possible.
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What is the shape of an atom with lone pairs of electrons in outer shell?
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>Pyramidal
>107 degrees |
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What is the shape of an atom with two lone pairs of electrons in outer shell of negative ion?
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>Square planar
90 degrees |
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What happens to the shape of a molecule when a bonding pair of electrons is replaced with a non-bonding pair?
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It squeeze the angle between each of the bonded pairs closer by approx 2.5 degrees.
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Define the term macromolecular.
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Many atoms joined together in a regular array by a large number of covalent bonds.
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Define the term polar bond.
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A covalent bond where the shared pair of electrons is displaced to one end.
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What groups of elements are ionically bonded?
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1-2 and 6-7
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