Different metals have different characteristics and there are many reasons to those variations. Physical properties and chemical properties of metals mainly depend on the electron configuration of metal atoms. In this tutorial, we will discuss why metals show different characteristics in physical and chemical properties.
Metals are located in all blocks in periodic table. ( s block, p block, d block, f block). But their characteristics such as chemical reactivity are very much different from metal to metal.
|Alkali Metals - IA Group||Li, Na, K, Rb, Cs, Fr|
|Alkali Earth Metals - IIA Group||Be, Mg, Ca, Sr, Ba, Ra|
|IIIA Group||Al, Ga, In, Tl|
|IVA Group||Ge, Sn, Pb|
|VA Group||Sb, Bi|
|3d Metals||Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn|
Metals prefer to eliminate electrons in their last shell. Therefore they form cations. Also oxidation number of a metal in a compound is always a positive value.
d block metals show variable oxidation numbers. As an example, ion can show +2 and +3 oxidation numbers when ion forms compounds. According to the oxidation number, colours, solubility and more parameters are changed. Few examples are shown below.
Sodium, a s block metal reacts with water very vigorously to give sodium hydroxide and hydrogen gas. But lead, a p block element does not reacts with water. Both are metals. But they have different characteristics.
Both lithium and beryllium are s block metals. But only lithium reacts with water.
In this section, you will see why and how physical properties of metals are changed from one metal to another metal.
Atomic volumes of 3d elements are lower than those of s block metals due to increased nuclear charge. Therefore density of 3d elements are much higher than s block elements.
Metals are good electric and thermal conductors. Silver is the best electric conductor in the world and copper is the second one. Free electrons in the metallic lattice are free to move. That's the reason why metals become so good electric and thermal conductors.
Alkali metal series (group IA) is chosen to discuss this variation.
Metallic characteristics decreases along the period when going from left to right. When consider sodium, magnesium and aluminium, sodium has the best metallic characteristic while aluminium is the lowest from those three.
First, we see some metals from different blocks to get an idea how melting and boiling points are varied. Consider sodium, aluminium and vanadium as metals.
We know, melting and boiling points of metals mainly depends on the strength of metallic lattice. The stronger the metallic lattice, melting and boiling points are increased.
Aluminium has a strong metallic lattice than sodium. So melting and boiling points of aluminium is higher than sodium. Vanadium has the highest melting and boiling point in 3d electrons because it's metallic lattice is very strong. Vanadium can participate five electrons to the metallic lattice while sodium and aluminium can participate one and three respectively.
s block elements are soft and have lesser melting and boiling points than d block metals.
In a same period, group 2 metals have higher melting and boiling points than group 1 metals.
Usually electronegativity of metals are less than non-metals. Electronegativity of sodium and oxygen are 0.9 and 3.5 in pauling scale (fluorine has the maximum value of 4.0). 3d metals have higher electronegativity than s block metals.
Metallic characteristic depend on easiness of valence electrons removing. If a metal can remove its valence electrons easily, they have good metal characteristics.
Many compounds of the transition elements (contains 3d) are paramagnetic due to partially filled electron shells. No magnetism is shown by alkali metals and alkali earth metals.
Due to presence of free electrons which are movable. Number of free electrons are depend on the valence of the metal. Also according to the crystal structure of metal, conductivity vary.
You will see, most of the good conductors are transition metals. There are not s block metals in good conductors list. But s block metals are also conductors.
Transition metals (3d metals) and their compounds can behave as catalysts. Alkene hydrogenation is catalyzed by Ni or Pt or Pd metals. But s block elements are not shown catalyst behavior as 3d metals.
Also 3d elements, aluminum compounds can act as catalysts. Anhydrous aluminium chloride (AlCl3) is used to benzene alkylation and chlorination as a catalyst. Aluminium is p block element.
s block metals are more reactive than d block metals. From s block metals, alkali metals are much reactive than alkali earth metals .
Let's take some metals, potassium (group 1), calcium (group 2) and iron (3d metal) reactions with water.
So, it is clear that, potassium is the most reactive element in those three elements and iron is the lowest reactive element.
Reaction of metals with oxygen explains the metals' reaction characteristics very nicely. Metals reacts with oxygen and produce metal oxides. When a metal exposes to the air, an oxide layer is formed on the metal.
In a oxygen stream, very reactive metals such as sodium, potassium, rubidium give peroxide and super oxide as products.
Metals except (copper, mercury, silver and gold) react with dilute acid and produce salt and hydrogen gas. As with other reagents, s block metals react very quickly with dilute acids.