bonding (phys I) Flashcards
why does bonding occur?
so elements obtain a noble gas structure
(no charge)
ionic bonding
- occurs when 2 elements have a large diff. in electronegativity
- result of strong es. forces of attr. between oppositely charged ions
structure of ionic compounds
giant, regular lattice
properties of ionic compounds
- high m.p –> strong es. forces of attr. –> lots of energy needed
- only conducts electricity if molten or dissolved in sol. (ions free to move & carry charge)
- brittle –> oppositely charged ions repel each other if adj
metallic bonding
result of es. forces of attr. between +ve metal ions & sea of delocalised electrons
structure of metallic compounds
giant lattice of +ve metal ions with delocalised electrons moving in between
properties of metals
- high mp –> strong es. forces –> lots of energy needed
- conducts electricity –> delocalised electrons can move & carry charge
- malleable –> attr. similar in all directions –> planes of ions can slide over each other
- shiny
covalent bonding
- occurs when 2 elements have small diff. in electronegativity
- electron pair shared between 2 atoms
(forms either simple molecule or macromolecule)
define dative cov. bonding
(or coordinate cov. bonds)
a cov. bond in which both electrons are donated from the same atom
(in diagrams, arrows used to represent dative cov. bonds)
properties of simple covalent molecules
- can be solids, liquids, gases
- low m.p –> helt together by weak WDWs –> little energy needed
- can’t conduct electricity
specific types of macromolecules
- graphite
- diamond
- iodine
- ice
structure of graphite
C atom cov. bonded to 3 others –> trigonal planar shape
properties of graphite
- high m.p –> many strong cov. bonds
- conducts electricity –> delocalised electrons between layers
- soft –> weak VDWs between layers –> can slide over each other
struc of diamond
C atom cov. bonded to 4 others –> all repel each other –> tetrahedral shape
properties of diamond
- high m.p –> many strong cov. bonds
- doesn’t conduct electricity
- hard
define electronegativity
the power of an atom to attract a pair of electrons in a covalent bond
why does electronegativity increase across a period?
no. of protons increases –> atomic radius decreases
types of intermolecular forces
- VDWs (temp dipole-dipole induced attractions)
- permanent dipole-dipole forces
- hydrogen bonds
how do VDWs arise between molecules?
- electronic distribution in molecule = asymmetrical due to random movement of electrons –> cause temp. dipole
- temp dipole induced in neighbouring molecule
- temp dipoles attracted to each other
permanent dipole-dipole forces
- occurs in polar molecules —>
large difference in en. leads to bond polarity - & there is attraction between S+ of one molecule and S- molecule
hydrogen bonds
- occurs when hydrogen is directly bonded to N,O,F
- strongest im force
(when drawn, lone pair needs to be shown on N,O,F & draw partial charge)
