. Experiments with Metals and Ions of Metals
Metals are similar in their physical properties in general, but they are not identical. Most of the metals are solids; few of them are liquids, such as mercury and cesium. Density of metals is not similar also. For example, sodium has density of 0.97g/cm3 while lead has density of 11.4g/cm3. Melting point of sodium is 98.0oC while for lead it is 327.6oC. Metals have the capability to lose electrons when they react with non-metals such as O2, halogens, water, acids and other metal cations. Metals react with non-metals but each to a different extent. The most reactive metals are alkali metals (group1A, where group is a vertical column in the periodic table), which include lithium, sodium, potassium, rubidium, cesium and francium. All these metals have one electron in the valence electrons' shell; this electron can be removed relatively easily, which means that this electron has a very small ionization energy. If we look closely at the elements of this group, we can see that they are not reactive to the same extent. This is because electrons have a negative charge and they are attracted to the nucleus, which has a positive charge. Valence shell electrons are responsible for the reactivity of an element; as the distance between valence electrons and the nucleus increases, the attractive force decreases and so the energy needed to separate the valence electron from an atom (ionization energy) decreases. So we can say that as the size of a metal atom increases, its ionization energy decreases and its reactivity increases (the most reactive alkali metal is francium and the least reactive one is lithium). An example of the reactivity of alkali metal is their reaction with water. For example: Na (s) + 2H2O → 2Na+(aq) + 2OH -(aq) + H2 (g) + heat
We can identify this reaction by the following
1- H2 gas emerges
2- Disappearance of metals
3- Heat produced
4- The appearance of hydroxide ions (OH-(aq)) makes the solution basic, which can be identified by using phenolphthalein as the indicator.
We can compare between the metals by the rate of production of H2(g) as well as by the heat produced from this reaction. Alkaline earth elements (group IIA) are active metals but less than alkali metals. Since calcium is larger than the magnesium atom, its ionization energy is smaller than that of magnesium. Thus, calcium is more reactive than magnesium. The other metals as aluminum, zinc, iron, lead and copper do not react with water, so we can’t use water to distinguish between their reactivity. HCl(aq) is used to put them in order according to their reactivity. We can put the most common metal in a series according to their reactivity (from the most to the least reactive one). “Potassium, sodium, lithium, calcium, magnesium, aluminum, zinc, iron, lead, copper, silver……”. When a metal in the upper part of the reactivity series reacts with aqueous solution of other metal ions lower in the series, the more reactive metal loses its electron more easily than the less reactive metal. As a result, the more reactive metal transfers its electrons to the less reactive metal. According to this reactivity series, we can predict what will happen when a piece of zinc metal is put in CuSO4 (aq) solution or in MgSO4 (aq) solution. Since Zn is more reactive than Cu, when we put Zn in CuSO4(aq), a reaction will occur as follows: Zn (s) + Cu2+(aq) + SO42- (aq) → Zn2+(aq) + SO42- (aq) + Cu (s) However, Since Zn is less reactive than Mg, if we put Zn in MgSO4(aq) there will be no reaction at all: Zn (s) + Mg2+(aq) + SO42- (aq) → No reaction.
10 mL Cu2+(aq) solution 0.5M
10 mL Ag+(aq) solution 0.5M
10 mL Mg2+(aq) solution 0.5M
10 mL Zn2+(aq) saturated solution
Pieces of the metals: Mg(s), Zn(s), Ag(s), Cu(s) 1cm x 1cm each. ...
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