Structure and Bonding 1 - Types of Bonding Flashcards
what do atoms want to achieve when bonding and why?
a full outer shell, in order to achieve a noble gas configuration, (most stable)
how is an ionic bond formed?
a metal transferring electrons to a non-metal
define ionic bond
the bond that is caused by the electrostatic attraction between a positively charged ions (cations) and a negatively charged ions (anions) in a lattice
give the charge on a sulphate ion
SO4 2-
give the charge on a hydroxide ion
OH -
give the charge on a nitrate ion
NO3 -
give the charge on a carbonate ion
CO3 2-
give the charge on an ammonium ion
NH4 +
how do you tell the charge of an ion using the periodic table?
group 1 = +1
group 2 = +2
group 7 = -1
group 6 = -2 etc
which 2 factors affect the strength of an ionic bond? what can these be refered to as together?
the size of ions and the magnitude of charge on ions, can be taken together as SURFACE CHARGE DENSITY, charge / SA
how does the size of an ion affect the strength of an ionic bond?
charges closer together will form stronger electrostatic forces
how does the magnitude of charge on an ion affect the strength of an ionic bond?
ions with higher charged will form stronger electrostatic forces
describe the structure of an ionic crystal
a giant crystalline lattice composed of repeating positive and negative ions
explain what the coordination number in NaCl is a why?
coordination number = 6
because in the 3D lattice each Na+ is in contact with 6Cl-
describe the position and movement of ions in a solid ionic compound.
what happens when a solid ionic compound is heated?
in a solid ionic compound the IONS are not free to move, and vibrate about a fixed position.
when a solid ionic compound is heated the ions vibrate more strongly, and are free to move
state the 4 properties of ionic compounds
1) high melting points
2) don’t conduct when solid
3) conduct when molten or aqueous
4) often water soluble
explain why ionic compounds have high melting points
the strong electrostatic forces of attraction between oppositely charged ions requires a lot of energy to overcome
explain why ionic compounds don’t conduct electricity when solid
the ions are about fixed positions throughout the lattice and so cannot move or carry charge
explain why ionic compounds conduct electricity when molten or aqueous
ions are free to move and carry charge throughout the structure
state the test for an ionic compound.
how do you spot one?
electrolyse it
it will conduct when molten or aqueous but not when solid, and consists of a metal and a non-metal
how is a covalent bond formed?
when atoms share pairs of electrons
define covalent bond
the bond that is formed by a shared pair of electrons between 2 non-metals
state the two types of covalent molecules
simple molecular and giant covalent (macromolecular)
what’s the one thing to remember when drawing dot and cross diagrams?
the group which an element occupies dictates the number of electrons that it has in its outer shell in its natural state eg. group 7 will have 7e- in its outer shell
define lone pair
a lone pair of electrons is a pair of electrons which are not used in bonding
define bonding pair
a bonding pair of electrons is a pair of electrons which are used in bonding
draw dot and cross diagrams for the following, and circle the lone pairs of electrons in each:
H2
Cl2
H2O
NH3
CH4
(check against notes)
what is meant by an electron deficient atom and give an example
an electron deficient atom is one which does not manage to share 8 electrons when forming a compound, eg. Be in BeCl2
identify the electron deficient atom in the following
BF3
AlCl3
(check diagrams against notes if used)
B
Al
why do some atoms have more than 8 electrons in their outer shell?
because they use vacant 3d orbitals
which atoms use vacant 3d orbitals in the following
PCl5
SF6
(check diagrams against notes if used)
P and S use vacant 3 d orbitals
define dative covalent/coordinate bonding
a covalent bond where one element provides both of the bonding pair of electrons
state the requirement for a dative covalent bond
an atom or molecule which is electron rich, and one which is electron deficient
explain how a dative covalent bond is formed
the element with the lone pair donates both to the deficient atom to form a new dative covalent bond
which alternative notation can be used for dative covalent bonds and what is its convention?
arrows
show where electrons are being donated TO, beginning from the electron rich atom/molecule and ending up at the deficient one
draw the bonding in the following
NH4+
H3O+
NH3 + BF3
CO
check against notes
state 2 properties of covalent compounds
low melting points
don’t conduct
explain why covalent compounds have low melting points and don’t conduct
low melting points: strong covalent bonds between atoms themselves but weak intermolecular forces don’t require a lot of energy to overcome
don’t conduct: no free electrons
give an example of a simple molecular crystal structure.
draw a diagram to show how they’re soft and break easily
iodine
diagram must name vdw IMF, check against notes
describe the structure of a macromolecular compound
a giant covalent lattice with very strong covalent bonds throughout
name the 3 examples of macromolecular compounds
diamond
graphite
graphene (1 layer of graphite)
describe the structure of diamond
each carbon atom is covalently bonded to 4 others in a repeating tetrahedral pattern
describe and explain the properties of diamond
high melting and boiling points, hard
many strong covalent bonds require a lot of energy to overcome
describe the structure of graphite
a layered structure where each carbon atom is covalently bonded to 3 others, leaving one free delocalised electron per carbon atom. weak forces between the layers
describe and explain the properties of graphite, (and by extension where applicable, graphene)
can conduct electricity as the one free delocalised electron per carbon atom is free to move and carry charge throughout the structure
graphite is used in lubricant as the weak intermolecular forces allow the layers to slide over one another
define metallic bonding
a regular arrangement of positive metal ions surrounded by a sea of delocalised electrons
which 2 factors can affect the strength of a metallic bond, and what are they known as collectively?
- atomic radius
- magnitude of charge
known as surface charge density collectively
state and explain the 4 properties of metallic bonding
1) conducts electricity: delocalised electrons are free to move and carry charge throughout the structure
2) conduct heat: vibration of positive ions
3) high melting and boiling points: the strong forces of electrostatic attraction between oppositely charged ions require a lot of energy to overcome
4) malleable and ductile: the regular arrangement of ions allows them to slide over one another
