Intramolecular forces (BondingCharacteristics of Crystals)

What is intramolecular force?

bonds within a molecule that hold the atoms together

What are lattice structures?

repeating, periodic 3D arrangements of interconnected unit cells found in nature and engineering 

What are lattice points?

represents the position of a repeating unit (like an atom, ion, or molecule) in a crystalline

(type of solid material where the atoms, ions, or molecules are arranged in a highly ordered, repeating pattern that extends in all three spatial dimensions.)

What are the 4 types of crystals?

ionic, covalent network, metallic, covalent molecular

What is metallic bonding?

bonds between a metal and metal

Describe metallic bonding (2)

• atoms have low IE, it takes very little energy to remove an e^- (e.g. being at room temp creating cations)

• atoms have low EA, means that other atoms are not willing to take in the lost e^- 

  • thus, the lost e^- “wonders around”

Lattice structure of metallic bonds

• cations form the lattice points of a network with the e^- floating in a sea around them

  • The structure is held together by electrostatic forces (attraction between opposite charges) between the cations and e^-

6 metallic crystals properties

• metallic bonds (50-800 kj/mol)

• high melting and boiling points

• very high electrical and thermal conductivity

• usually malleable and ductile

• hard

• insoluble

4 factors affecting metallic crystal properties

• charge on cation

• cationic radius

• # of electrons in the “sea”

• impurities (alloys)

What is ionic bonding?

bonds between metal and non-metal

Describe ionic bonding (2)

• metal has low IE and will readily giving up its e^- to form a cation

• non-metal  has high EA which means that it will take loose e^- to form an anion

• cation and anion are then bonded together by electrostatic force of attraction

Lattice structure of ionic bonds

• lattice structure that is created  alternates cations and anions (ions) at the lattice points

  • These bonds lock the ions into place so that they don’t move freely

6 ionic crystals (salts) properties

• ionic bonds (600-4000 kj/mol)

• high melting point and boiling point 

• electrical and thermal conductivity depends on the state of the ionic crystals

  • poor conductors as solids (when ions are locked in place)

  • good conductors as aqueous (when ions are free to move)

• brittle

  • ionic crystals are not malleable because the ions are locked into place 

    • when a force is applied, it can push the ions down one row, so that the anions are lined up (and the cations are lined up)

    • this causes the crystal to repel and shatter

• hard 

  • because ionic bonds are quite strong 

• generally soluble in polar solvents

5 factors affecting ionic crystal properties

• charge on cation

• charge on anion

• packing of ions

• ratio of ions involved

• impurities

What is covalent bonding?

bonds between non-metal and non-metal

Describe covalent bonding (2)

since both atoms are non-metals they:

• both have high IE, neither is willing to give up any valence e^-

• both have high EA, both try to grab onto additional e^-

• This results in the sharing of e^- between the 2 nuclei

What are the 2 types of lattice point a covalent molecular can have?

non-polar and polar covalent

non-polar covalent

• ΔEN < 0.4

• pure covalent bond

• equal sharing of electrons between the 2 nuclei

polar covalent

• 0.4 < ΔEN < 1.7

• unequal sharing of electrons between the 2 nuclei

  • partial positive charge (δ⁺) on the atoms with lower EN

  • partial negative charge (δ^-) on the atom w/ higher EN

6 non-polar covalent crystals properties

• dispersion forces (0-50 kj/mol)

• very low melting and boiling points

• extremely low electrical and thermal conductivity

• extremely fragile (in terms of malleability and ductility)

• very soft (in terms of hardness)

• soluble in non-polar and slightly polar solvent

6 polar covalent crystals properties

• hydrogen bonding or dipole-dipole

• low melting and boiling points

• very low electrical and thermal conductivity

• fragile (in terms of malleability and ductility)

• soft (in terms of hardness)

• generally soluble in polar solvent

6 covalent network properties

• covalent bonds 300-800 kj/mol

• very high melting and boiling points

• low electrical and thermal conductivity (with some exceptions)

• not malleable or ductile

• very hard (in terms of hardness)

• insoluble

(lattice points are atoms)

What are the 4 bonds intramolecular can form?

• single bond

• double bond

• dative bond/ coordinate covalent bond

• triple bond

What are allotropes? (2)

• Different structural forms of the same element

• Exist in the same physical state, but have different arrangements of atoms and have different properties

What are 3 allotropes of carbon?

diamond, graphite, and fullerenes (buckyball)

What are 3 allotropes of silicon?

asbestos, mica, and quartz