Bonding 1-2 Flashcards
When does ionic bonding occur
Metal + non metal
Electron transferred
When does covalent bonding occur
When does covalent bonding occur
When does metallic bonding occur
Metal and metal
Electron pooled
Why do chemical bonds occur
As they lower the potential energy between charged particles that constitute atoms
Potential energy : The stored desire between bonding atoms to repel each other as when two nuclei are pushed together protons are pushed together which repel
Compare electronegativity of ionic and covalent bonds increasing
Pure covalent (equally shared)-polar covalent (unequally shared )-Ionic transferred
What occurs during ionic bond
The metal loses an electron electron due to low ionisation energy :energy required to remove an electron )
The non metal gains an electron due to high electron affinity
What’s ionisation energy of cation -metal to lose electron
Ionisation energy is endothermic
What is the acceptance of an electron by non metal
Exothermic
Which is larger ionisation energy or acceptance of an electron
Ionisation energy is larger then acceptance of electron
However heat formation of ionic compound is generally an exothermic value
What’s the energy difference due to
Energy difference is due to formation of highly ordered structure known as crystal ionic structure
Where are valence electrons
Valence electrons are the outermost electrons in an atom
What does Lewis theory say
Electrons are transferred from one atom to another forming ions . One atom must lose a valence electron whilst other must gain
What are elements with low ionisation energy known as
Electropositive
What are elements which require electrons more readily known as
Electronegative
What are properties of ionic compounds
Larger ion, weaker attraction and hence
lower lattice energy.
• Larger charge, stronger attraction and
hence higher lattice energy.
• Ionic compounds have high melting points (and boiling points).
• All ionic compounds are solids at room temperature.
• Hard and brittle crystalline solids – many are soluble in water.
What’s the Lewis theory applied to covalent bonds
The Octet rule still applies, but now the
atoms achieve their octet by sharing
electrons.
* A bond consists of a shared pair of
electrons.
How does chlorine create covalent bonds
Cl + Cl Cl2
Chlorine has seven valence electrons (3s2 3p5)
Sharing of the unpaired 3p electrons filled outer shells
What are electrons which aren’t shared known as
Electrons that are not shared between
atoms are called lone pairs of electrons
What’s the shape of molecule determined by (covalent bonding )
The shape of the molecule (covalent
bonding) using this theory is explained by
electrostatic repulsion between electron-
pair bonds and also lone pairs.
What pattern do elements in first period tend to follow
C = 4 bonds and no lone pairs.
• N = 3 bonds and 1 lone pair.
• O=2 bonds and 2 lone pairs.
• H = 1 bond, no lone pairs.
• Halogens = 1 bond and 3 lone pairs
What’s a polar covalent bond
Covalent bonding between two different
atoms, e.g. hydrogen and chlorine gives rise to
a covalent bond where the two electrons
(bond) are shared unequally.
• We have a polar covalent bond.
• The polar covalent bond has a polarity, i.e. one
end of the bond has a small positive charge
(hydrogen; relatively electron deficient),
whilst the other end has a small negative
charge (chlorine; relatively electron rich)
What are some examples of polar covalent bonds
HCL H2O NH3
These molecules have a dipole
What are examples of electronegative elements
Chlorine
Florine
Bromine
Oxygen
Nitrogen
Calculation for size of dipole
Size of dipole indicated by dipole moment (µ)
µ = e x d
where e = magnitude of charge on an atom (δ+ or δ-)
and d = distance between the two charges
The unit of m is the debye (D)
