bonding structure, energy changes, and properties Flashcards
melting definition
melting requires enough energy to disrupt the bonds between atoms/molecules/ions/metal atoms
metal definition
metals are:
- made up of metal atoms
- held together in a 3D lattice by metallic bonding
- this is the strong attraction between the positively charged nuclei of the atoms and the delocalised valence electrons
melting point of metal
high
why is melting point of metal high
the 3D lattice of metal atoms surrounded by a sea of delocalised valence electrons are strongly attached to the nuclei in the lattice which forms strong metallic bonds therefore a large amount of energy is required to break
electrical conductivity
electrical conductivity requires a substance to have mobile charged particles
do metals conduct electricity
yes
why do metals conduct electricity
the valence electrons are free to move throughout the structure
why are metals malleable/ductile
the metallic bonds are non-directional as the electrons are delocalised across the lattice therefore when a force is applied the atoms are free to move without disrupting these bonds meaning the structure can change shape without breaking the lattice
are metals soluble in water
no
why are metals insoluble in water
there is no attraction between the metal atoms and polar water molecules
ionic bonding definiton
ionic substances are made up of ions held together by a 3D lattice by ionic bonding. This is strong attraction of positively charged cations and negatively charged anions
boiling definition
boiling requires supplying enough energy to break the bonds between the ions
why do ionic substances not conduct electricity in the solid state
in the solid state the ions are rigidly held in a lattice by strong ionic bonds, so cannot move around so cannot conduct electricity.
when can ionic substances conduct electricity
when molten (l) and in solution (aq)
why can ionic substances conduct electricity when molten and in solution
the ions are able to move freely so can conduct electricity
are ionic substances malleable/ductile
no
why are ionic substances not malleable/ductile
if a force is applied to an ionic lattice it forces ions with the same charge next to each other which repel and the lattice structure breaks meaning ionic substances are brittle
why are ionic substances soluble in water
an ionic solid is soluble because the force of attraction between the ions and water is strong enough to overcome the forces holding the ions together along with the forces holding the water molecules together
how do ionic substances dissolve in water
when an ionic substance dissolves in water it separates into its ions, the ions are charged and attracted to the charged ends of the polar water molecule. slightly negative charges on oxygen ends of water molecules attract to positive ion, slightly positive hydrogen ends attract to negative ions. causes ions to be surrounded by water molecules and the lattice breaks down
covalent bonding definition
strong attraction between the two positive nuclei and one or more shared pair of electrons
covalent networks defintion
covalent network solids are made up of atoms held together in a 3D or 2D lattice by covalent bonding. this is the strong attraction between positive nuclei and shared electrons
covalent network melting point
high
why is covalent network melting point high
made up of atoms held together in a 3D lattice (or 2D) by strong covalent bonding, these bonds require a large amount of energy to break
which lattice in covalent network conduct electricity
2D lattices - graphite and graphene
why do 3D lattice’s not conduct electricity (covalent network)
all of the valence electrons for each atom (C or Si) form covalent bonds, therefore there are no delocalised valence electrons free to move
why do 2D lattices conduct electricity (covalent network)
in graphite and graphene each carbon is bonded to 3 other carbon atoms, this leaves one delocalised valence electron from each carbon atom, these electrons are free to move
draw ionic solubility diagram
refer to notes
are covalent networks soluble in water
no
why are covalent networks insoluble in water
the interaction between the polar water molecule and the atoms is not strong enough to attract the atoms out of the lattice
are covalent networks malleable/ductile
no
why are covalent networks not malleable/ductile
if a force is applied the directional strong covalent bonds have to be broken before the atoms can move, resulting in breaking the lattice
hardness, diamond vs graphite
all the forces of attraction in the 3D lattice of diamond are strong covalent bonds which makes the structure very rigid and gives the property of hardness. In graphite the forces of attraction between the 2D layers are weak allowing the layers to slide over one another making it soft.
covalent molecule definiton
molecular substances are made up of discrete neutral molecules with weak intermolecular forces between the molecules
what are the 2 types of forces to consider in covalent molecules
- strong covalent bonds between the atoms in the molecules
- weak intermolecular forces between the molecules
melting point in covalent molecules
low
why is the melting point low in covalent molecules
because the forces are weak they require a small amount of energy to separate the molecules
do covalent molecules conduct electricity
no
why do covalent molecules not conduct electricity
molecular substances are made up of discrete neutral molecules, because they are neutral they are unable to conduct electricity
do polar molecules dissolve in water
yes
what dissolves in water
polar molecules dissolve in water.
why are polar molecules soluble in water
because the 𝛿−ve oxygen end of the polar water molecule attracts the 𝛿+ve end of the polar molecule and the 𝛿+ve hydrogen attracts the 𝛿−ve end of the polar molecule allowing them to mix
why are non-polar molecules insoluble in water
the 𝛿−ve oxygen and the 𝛿+ve hydrogen ends of the polar water molecule attracts adjacent water molecules, because the non-polar molecule has no 𝛿−ve and 𝛿+ve end it does not attract with the polar water molecules preventing them from mixing
do non-polar molecules dissolve in water
no
VSEPR, shape ‘code’
the shape and angle is controlled by minimising repulsion of the electron areas around the central ….. atom. The electron arrangement that minimises repulsion for …. electron areas is …. which results in an angle of …. Because …. electron areas are bonding and … non bonding, it results in a …. shape with a bond angle of ….
VSEPR, compare and contrast
consider, what is similar & what is different:
- total electron areas
- bond angles
- bonding electron areas
- non-bonding electron areas
- shape name
VSEPR, compare and contrast
consider, what is similar & what is different:
- total electron areas
- bond angles
- bonding electron areas
- non-bonding electron areas
- shape name
compare and contrast the shapes and bond angles of H2O and SO2
refer to notes
compare and contrast the shapes and bond angles of H2O and NH3
refer to notes
what do polar molecules require
an uneven spread of charge over the molecule
how to identify if a molecule is polar
1- there are different terminal atoms
2- there are lone pair(s) (non-bonding electrons) around the central atom
OTHERWISE the molecule is NON-POLAR
polarity code:
1- define the requirements of molecular polarity
2-describe the polarity of individual bonds using electronegativity
3-link the molecules shape to symmetry and thus the effect on bond dipoles
molecular polarity definition
molecular polarity is the distribution of charge about the central … atom
polarity code for CCl4
refer to notes
polarity code for H2O
refer to notes
polarity code for COCl2
refer to notes
solubility
like dissolves like
do polar molecules dissolve in cyclohexane
no
why do polar molecules not dissolve in cyclohexane
because the 𝛿−ve and 𝛿+ve ends of the polar water molecule are attracted to 𝛿−ve and 𝛿+ve ends respectively of neighbouring polar molecules. The non-polar cyclohexane has no 𝛿−ve and 𝛿+ve ends, meaning they are unable to mix
do non-polar molecules dissolve in cyclohexane
yes
why do non-polar molecules dissolve in cyclohexane
because the non-polar molecule has no 𝛿−ve and 𝛿+ve end the two substances have similar intermolecular forces which allows them to mix
