Bonding
Metallic Bonding
Metals are found on the left hand side and centre of the periodic table
Metals
metal atoms have a week hold on their outer shell [valence] electrons
gives valence electrons freedom to move throughout the metal
moving down a group of metals they become more reactive
loses electrons to become cations
electrons from metals form a sea of electrons
electrons are delocalised/free moving
-/+ attract: electrostatic force provides multidirectional bonding between the positive ions and negative electrons [metallic bonding]
Properties of metals
physical properties
conducts heat
conducts electricity
generally high melting point and boiling point
malleable [hammered]
ductile [drawn into wires]
metalic lustre [shiny]
opaque [light bounces off]
Name of property | Description of property | How does metallic bonding allow for this property |
|---|---|---|
Melting/boiling point | Generally high due to strength of bond. When molten bond still there but order has been broken. Bond breaks when boiling. | Strength of bond determines it’s high or low tolerance |
Electrical conductivity | Valence electrons in sea are free to electrical potential. Electrons aren’t attracted to specific nucleus, so as another replaces them they are free to go. | No bond yet so free to move |
Malleable/ductile | Electrons in sea enable atoms to roll over one another when stress is applied [permanent change] | Electrons are moving around a lot meaning spaces for nucleus to move |
Thermal conductivity | Good at heat conduction as heat is picked up by electrons and heat is transferred by moving electrons | Electrons are moving about so they can carry it along |
Ionic Bonding
Atoms and Ions
atoms are neutral
if an electron is added or removed the atom becomes charged and is now called an ion
Cation
an electron is removed and becomes positive
forms when valence shell is mostly empty
comes from metal atoms
electrons are weakly bound to atom
common cations: hydrogen ion+, lithium ion+, sodium ion+
Anion
electron added to atom and becomes negative
forms when valence shell is almost full
comes from non-metals
common anions: fluoride ion-, chloride ion-, sulfide -2
Polyatomic Ions/Radicals
2+ atoms
example: hydroxide
Ionic Bonding
metals + non-metals
non-metals pull electrons from metals forming anion and cation
electrostatic force pulls ions together forming a strong ionic bond
electrons are donated
example: ammonium = NH4+
Writing a formula of an ionic compound
write the formulae of ions present [with charges]
Pb4+ O2-
`cross over’ the charges, so that the charge of the first ion becomes the subscript No. for the 2nd ion [vise-versa]
Pb2 O4
if needed simplify
PbO2
Writing name of an Ionic Compound
metal then non-metal[s]
metals name doesn’t change
non-metal generally changes suffix to 'ide’
if oxygen bonded suffix may become
ite’ or`ate’
Covalent Bonding
Non-metals
Displays opposite properties to metals
poor conductors of heat and electricity
low melting/boiling points
brittle
not ductile
dull
not as reactive
Covalent Bonding
non-metallic atoms bond with each other
they share some of their outer-shell electrons
covalent bonds happen when two non-metals share one or more pairs of their outer shell electrons to only fill their outer shell
2 atoms are bonded due to the electrostatic attraction of the shared electrons and the positive nucleus of each atom
No. of electrons = No. of covalent bonds
usually results in the formation of discrete grouping [molecules or covalent molecular substances] e.g. water
can form 3D lattices [covalent network substance] e.g diamonds
Naming Covalent Molecules
1st non-metal then 2nd but change 2nd suffix to ide
use prefix mono, di, tri, tetra, etc to indicate number of atoms in each
if the 1st element has one keep the same
e.g. Phosphorus Trichloride, Dinitrogen Pentoxide