HUBS1403 Lecture Notes - Lecture 3: Volumetric Heat Capacity, Molar Concentration, Acid Strength
Chemical Bonds and Shapes
Chemical Bonds
Three types
• Hydrogen bonds (weak)
• Ionic bonds (strong)
• Covalent bonds (very strong)
Each type has different strength which allows different interactions to occur
Ionic Bonds
Chemical bonds created by the electrical attraction between cations (+ve) and anions (-ve)
Covalent Bonds
Some atoms complete their outer shells by sharing electrons eg Methane - carbon atom with 4 in
outer shell + 4 hydrogen atoms with 1 electron in each outer shell = share the electrons and
therefore bond
Double covalent bond
• Sharing 2 pairs of electrons
Triple covalent bond
• Sharing 3 pairs of electrons
Types of Covalent Bonds
Non polar
• Electrons are shared equally
• The atoms remain electrically neutral
• Very strong
Polar
• Unequal sharing of electrons
• The atoms have slight +ve or -ve charge
• Eg water
Polar Covalent Bonds - water
• Unequal sharing of electrons
• Electrons spend more time orbiting the oxygen nucleus
o Small -ve charge
• Electrons spend less time orbiting the hydrogen nucleus
o Small +ve charge
Polar covalent bonds Facilitate hydrogen bonds
• The negative part of the water molecule attracts to the positive part of another molecule, this
bond is very weak although it is the reason insects can walk on water, it forms a film
Hydrogen Bonds
The attraction between a small +ve charge on the H atom of a polar covalent bond and a small -ve
charge on a neighbouring atom (usually O or N) of another polar covalent bond
• Weak attractive force
o Between adjacent molecules - properties of water - surface tension
o Too weak to create molecules
o Can be within the same molecule
Our existence depends on water
• Makes up 2/3 of total body weight
• Solvent
o Provides a medium for solutes
• Reactivity
Document Summary
Three types: hydrogen bonds (weak, covalent bonds (very strong) Each type has different strength which allows different interactions to occur. Chemical bonds created by the electrical attraction between cations (+ve) and anions (-ve) Some atoms complete their outer shells by sharing electrons eg methane - carbon atom with 4 in outer shell + 4 hydrogen atoms with 1 electron in each outer shell = share the electrons and therefore bond. Double covalent bond: sharing 2 pairs of electrons. Triple covalent bond: sharing 3 pairs of electrons. Non polar: electrons are shared equally, the atoms remain electrically neutral, very strong. Polar: unequal sharing of electrons, the atoms have slight +ve or -ve charge, eg water. Polar covalent bonds - water: unequal sharing of electrons, electrons spend more time orbiting the oxygen nucleus, small -ve charge, electrons spend less time orbiting the hydrogen nucleus, small +ve charge. Our existence depends on water: makes up 2/3 of total body weight.