Chemistry notes - Chemistry of Natural Resources, Elements from the Sea, Ions in Solids and Solutions

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Chemistry of Natural Resources

Elements from the Sea

Ions in Solids and Solutions


Ions in a solid are held together due to the attraction of the oppositely charged ions. This allows for a giant ionic lattice structure. Some molecules, such as sodium chloride, can be said to hold a simple cubic lattice structure. Also sometimes water molecules can be held within the lattice structure, and are known as water of crystallisation. The crystals are said to be hydrated.


Ionic substances dissolve in water and in doing so their ions become surrounded by water molecules due to their polarity. The negative end of the water molecule is attracted to the positive ion in solution, and the positive to the negative ion. This means that each ion is spread evenly throughout the solutions and behaves independently.

Ionic Equations

In ionic equations the spectator ions are taken out of the equation.

Ag + (aq) + NO₃¯ (aq) + Na+ (aq) + Br+(aq) AgBr (s)

Ag + (aq) + Br- (aq) AgBr (s)

These equations can also be used to summarise neutralisation reactions.

Concentrations of solutions

The following equation is used to find the concentration of a solution:

Concentration (moldm¯³) = Number of Moles / Volume (dm)

Atoms and Ions

The first ionisation enthalpy is the energy required to remove one mole of electrons, from one mole of isolated gaseous atoms of an element. This creates one mole of positively charged ions.

Across Periods

As you travel across the period on the periodic table, the energy required to remove an electron increases. This is because as you move across the period, more electrons are added to the same shell. This results in a greater attraction between the nucleus and the electron, so more energy is needed to remove the electron.

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Across Groups

As you travel down the groups on the periodic table, the energy required to remove an electron decreases. This is due to the increased distance from the electron to the nucleus, resulting in a decreased attraction between the two, and also due to the increased number of shells in between the two, resulting in more shielding, further weakening the attraction.

Successive Ionisation Enthalpies

Ionisation enthalpies increase after successive electrons are removed, due to the higher number of protons, giving a stronger attraction, therefore requiring more energy to remove.

Also there are sharp jumps as you move onto the ...

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