Bonding Flashcards
What are the 3 main bonding types?
Metallic
-metals bonding together
Ionic
-transfer of e to form positive and negative ions
-metals and non-metals
Covalent
-electrons are shared (attraction)
-non-metals
What is a valency?
The measure of combining ability of an atom with other atoms
-charge of an ion=valency
Structure of a metal bond
Lattice of metal ions embedded in a sea of delocalised electrons
-electrons are mobile
*practice drawing a picture with headings
Properties of a metal
-range of melting/boiling points
-good electric/heat conductors
-malleable
-lustre
-ductile
-high tensile strength
-hard
Explain why metals have high melting/boiling points
-attraction between metal ions and electrons must be overcome in order for metal to melt/boil
-attractive forces are strong due to opposing charges
-thus, higher melting/boiling point is required
Explain why metals are good conductors (heat and electricity)
Heat
-electrons move faster
-motion and energy transmitted through the lattice
-causing more vibration between particles and more collision
Electricity
-current in metal is electron flow
-as electrons repel, ones that are fed in a wire or rod of some sort will cause repulsion of electrons in the metal lattice
-and equal number of electrons will then be forced out of the wire onto the other end
Explain why a metal is malleable, tensile, and ductile
Malleable:
-can be shaped or beaten
Ductile:
-drawn into wire
Tensile strength:
-pulled until snapping
For both:
-cations in lattice are arranged in layers with no real bonds
-only attraction to the electrons
-layers can slip over each other but will stay intact
-thus, metals can be deformed without breaking
Explain why a metal has lustre
Light rays hitting the metal are reflected off of delocalised electrons
-close packing of metal ions prevent light from passing through
- e.g. opaque
Structure of ionic bond
Electrostatic attraction between positively and negatively charged ions arranged in a crystalline arrangement
Properties of ionic bonds
-strength (hard and brittle)
-good conduction of electricity (when dissolved)
-high melting point
What is an alloy?
A substance formed when other material are mixed with a metal.
E.g. Materials like carbon
Explain strength of ionic bond
Hard and brittle:
Can snap
-brittle because they can shatter easily when dropped
-attraction is strong but can be repulsed when layers shift
-no delocalised electrons
Explain the conductivity of ionic bonds
Is very good when the ionic compound is melted or dissolved
-can’t conduct when solid due to ions being in fixed layers (no free electrons)
-when melted, ions and electrons are free to move thus conduct (electrolysis)
Explain the melting/boiling point of ionic bonds
Solid at room temperature
-many non directional bonds held together by attraction of opposing charges
-with higher attraction=higher melting point
-no such thing as a single ionic bond i.e. no lattice
Structure of a covalent bond
Non-metals bond and share an electron to attain a full shell
-directional bonding
*practice drawing the diagram with headings
What is meant by covalent molecular?
Consists of a pair of electrons between two positive nuclei.
-the nuclei repel each other but are attracted by the pair of electrons
What is a covalent network?
Bonds between substances are covalent (share electrons) but th eparticles of which they are built are atoms so they can be giant atomic structures
-all atoms are linked and strong bonds
-continuous bonds (network)
-no separate molecules
e.g. diamond, graphite, silica
Properties of covalent bonds (molecular and network)
Molecular:
-low boiling point (weak intermolecular bonds)
-strong intramolecular bonds
-non-conductors (no free electrons)
-usually liquid/very soft
Network:
-high boiling/melting point
-non-conductors
What is an allotrope?
different forms of the same element
What are the allotropes of carbon?
Diamond, Graphite, Fullerenes
Properties of diamond
Carbon atoms bound to 4 neighbouring atoms (4 valence electrons)
-forms a 3D covalent network
-no weak intermolecular forces therefore:
-really hard
-high boiling point
-non-conductor
-unreactive
-non-malleable or ductile
Properties of graphite
High melting point.
Density lower than that of diamond.
It has soft, slippery feel
How do ions related to the properties of bonds?
-when atoms with similar ionic charges are bonded together, their electrostatic attraction is higher
-so things like melting point are higher
