Bonding (old) Flashcards
Description of ionic bonds
- metal and non metal
- transfer electrons
- opposite charged ions attracted by electrostatic forces
- in a giant ionic lattice structure
Properties of ionic compounds
- crystalline solid at room temp
- high m.p
- only conduct electricity when motlen or dissolved, ions now free to move to carry a current throughout the structure
- brittle and shatter easily
Why are ionic compounds brittle?
- because they form a lattice of alternating +/- ions, a small displacement move the ions and causes contact between ions with same charges
Why does ionic compounds have high melting point?
- need a lot of energy to break the giant lattice of ions with strong electrostatic forces between + - charged ions
Description of molecular covalent bonding
- in a simple molecular structure
- non metal non metal
- shared pair of electrons
Properties of molecular covalent bonding
- gas and liquid in room temp.
- low m.p.
- poor solubility
- don’t conduct electricity- not charged so no free ions, no delocalised electrons
Why is molecular Covalent bond has low m.p?
- weak intermolecular forces between MOLECULES so easy to break, less energy needed to overcome
- Types of forces : van der waals, permanent dipoles, hydrogen bonds
Why is molecular covalent has low solubility ?
- no charged particles
- don’t interact with polar water molecules
What affects the strength of covalent bond ?
- atomic radius- the bigger the atom is, the greater distance so weaker attraction between nucleus and electrons
Factors affect strength of ionic bonds (2)
- charge of ions- higher charge( more protons +) = stronger attraction of nucleus and e-
- size of ions - smaller ion( smaller atomic radius ) = less distance = stronger attraction of nucleus and e-
Description of macromolecular covalent bonding
- non metals x2
- shared pair of electrons
- macromolecular structure
E.g. diamond, graphite, silicon dioxide, silicon
Properties of macromolecular covalent bond
- solid at room temp.
- high m.p.
- insoluble
- diamond and sand don’t conduct electricity, graphite does as free delocalised electrons between layers
- don’t conduct when molten
Why is m.p high in macro.cov bond
- many strong covalent bonds in macro structure = need a lot of energy to break
Bonding + structure of diamond
- each C atom bond with 4 other tetrahedral arrangement
- does not conduct electricity but good thermal conductor
- very high m.p.
- extremely hard
Bonding + structure of graphite
- each C atom bond with 3 other C atoms , the 4th e- is delocalised
- hexagonal arrangement
- layered structure
- weak intermolecular forces between layers
- high m.p.
- insoluble, covalent bonds too strong to break
Why graphite is soft ?
- weak intermolecular force between layers = can slide over each other
why is graphite light weight ?
- layers are far apart compared length of covalent bonds= low density
Bonding and structure of metallic bond
- solid at room temp.
- metal x2
- giant metallic lattice structure
- electrostatic force of attraction between metal + ions / delocalised e-
Properties of metallic bond
- high m.p
- insoluble- as metallic bonds are non polar
- good conductor of electricity- delocalised electrons give charge to the whole structure
- malleable
Why is metallic bond high m.p.
- strong electrostatic forces between + ions and delocalised sea of e-
Factors affect metallic bond
- size of ions- larger ions = larger ionic radius = weaker attraction of positive ions to delocalised e- = decrease strength
- charge of ions- higher charge = stronger attraction of positive ions to delocalised e- = greater strength
Why metals are malleable ?
- layers of ion can slide over each other without any disruption to metallic bond = + ions still attract to delocalised e-
Why is alloy harder than pure metals ?
- a mixture of metals= different sized atoms distort regular layered structure so layers cannot slide = harder
