Physical and Chemical Properties of Beryllium and Lithium with Diagonal Relationship
In the periodic table, Group 1 elements, which include lithium, sodium, potassium, rubidium, francium, and cesium, are alkali metals. Group 2 elements, which include beryllium, magnesium, calcium, strontium, and barium, are alkaline earth metals. Lithium is the first element of Group 1, and Beryllium is the first element of Group 2 in the periodic table. Have you ever wondered what are the anomalous properties of lithium and beryllium, and why do they behave so differently?
Well, the reason for the anomalous behavior of lithium and beryllium is their small size. Here you will see what the properties of lithium and beryllium are and how they behave differently from other group elements.
Lithium and Other Alkali Metals
Nature: Lithium is a harder compound as compared to some other alkali metals.
The melting and Boiling Point of Lithium is higher, as compared to the other group elements.
Reactivity: Lithium is the least reactive metal out of all alkali metals.
Oxidation: Lithium is A strong reducing agent and thus Lithium is a weak oxidizing agent as compared to other alkali metals.
Solubility: The lithium compounds are moderately soluble in water, compared to other alkali metals, that are highly soluble in water.
Differences between Beryllium and Other Alkaline Earth Metals
Nature: Beryllium is known to be harder as compared to other group members.
Melting and Boiling Point: Beryllium has higher melting and boiling points.
Reaction: Beryllium does not react with water even at extraordinary temperatures.
Compound Formation: Group 2 members form ionic compounds as compared to Beryllium, which forms covalent compounds.
Beryllium Carbides: Beryllium carbides are covalent in nature while other carbides are ionic. Beryllium Carbide reacts with water to produce methane gas.
Coordination Number: Beryllium exhibits a coordination number of 4, whereas other alkaline earth metals can exhibit a coordination number of 6.
Why does Lithium Exhibit Different Properties from Other Group Elements?
The size of the atoms generally increases in a group while moving from top to bottom. Due to this reason, the polarizing power of the atoms decreases. Hence, lithium is an element that has a small size and high polarizing power. Additionally, lithium is tremendously electropositive in nature due to which it can form covalent bonds. To sum up, the anomalous behavior of lithium as compared to other alkali metals is due to the following reasons:
Small size
High polarizing power
Covalent nature of lithium compounds
What are the Major Differences between Lithium and Other Alkali Metals?
Nature: Lithium is much harder compared to other alkali metals.
Melting and Boiling Point: The melting and boiling point of lithium is higher as compared to other group elements.
Reactivity: Out of all the alkali metals, lithium is the least reactive metal.
Oxidation: Lithium is a strong reducing agent and hence a weak oxidizing agent in comparison to other alkali metals.
Solubility: The lithium compounds are moderately soluble in water in comparison to other alkali metals, which are extremely soluble in water.
Chemical Reactions: Lithium is the only alkali metal, which can form its monoxide. However, it is not capable of forming solid hydrogen carbonates. All the alkali metals can form ethynide except lithium, which does not react with ethyne. Moreover, it shows a slow reaction with bromine as compared to other group elements.
Why does Lithium show a Diagonal Relationship with Magnesium?
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Lithium has the smallest size in the alkali metal series. Along with it, lithium has a high polarization power. These properties of lithium are similar to magnesium, which is diagonally placed in the next series. Both elements show the following same properties:
The lithium and magnesium ions have comparable melting and boiling points.
They both form monoxides:
2Mg + O2 → 2MgO
They form nitrides by reacting with nitrogen:
Li(s) + N2(g) → 2Li3N(s)
They both form hydroxides and oxides by slowly reacting with water:
Mg(s) + 2H2O(g) → Mg(OH)2(aq) + H2(g)
Both LiCl and MgCl2 are soluble in ethanol.
Why does Beryllium show Anomalous Behaviour From the Other Group Elements?
The major reasons for the anomalous properties of beryllium are as follow:
Small atomic and ionic size
High ionization energy
Absence of d-orbital
Hence, there is an anomalous behavior of beryllium that can be observed.
Nature: Beryllium is quite much harder as compared to other group members.
Melting and Boiling Point: As compared to other alkali metals, Beryllium has higher melting and boiling points.
Reaction: All the members of group 2 react with water to form oxides or hydroxides except Beryllium. It does not react with water even at extraordinary temperatures.
Compound Formation: The group 2 members form ionic compounds as compared to Beryllium, which forms covalent compounds. Due to the covalent character, beryllium salts are certainly hydrolyzed (the bond breaks down when it reacts with water).
Beryllium Carbides: Generally, the carbides of Beryllium are covalent in nature instead of other member carbides, which are ionic. Additionally, Beryllium Carbide can react with water to produce methane gas. However, the carbide of other alkaline metals produces acetylene gas.
Coordination Number: Beryllium exhibits a coordination number of 4, whereas other alkaline earth metals can exhibit a coordination number of 6. It is because the valence shell of Beryllium has only 4 orbitals, namely; 1 s and p. That is why; it cannot show the coordination number of more than 4. However, other group elements can make use of d-orbitals and hence can exhibit a coordination number of 6.
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Why Beryllium shows Resemblance with Aluminium?
The oxides of both Beryllium and Aluminium are amphoteric in nature; that is, they show both acidic and basic nature. Both elements have the same polarizing power as well as electronegativity. Additionally, they both show reducing character due to which they exhibit the following properties similar:
Both AlCl3 and BeCl2 act as Lewis acids and have chlorine-bridged structures in the vapor phase.
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Due to the formation of protective film on the surface, both Be and Al are resistant to the exploitation of acids.
Both Beryllium and Aluminium dissolve in the strong alkalies and form soluble complexes.
Both the metals can form complexes due to similar polarizing power.
Hence, the anomalous properties of lithium and beryllium are due to their small size.
FAQs on Properties of Beryllium and Lithium in the Periodic Table
1. What are the main properties of beryllium and lithium?
The main properties of beryllium and lithium include low atomic mass, high reactivity (especially lithium), and strong polarising power (especially beryllium).
- Lithium (Li): Group 1 element, soft, low density (0.53 g cm-3), highly reactive, forms Li+ ions.
- Beryllium (Be): Group 2 element, hard, high melting point (1287°C), less reactive than other alkaline earth metals, forms Be2+ ions.
- Both show anomalous behaviour due to their small atomic size.
2. Why do lithium and beryllium show anomalous properties?
Lithium and beryllium show anomalous properties because of their small atomic size, high charge density, and relatively high ionisation enthalpy.
- They have the smallest size in their respective groups.
- Their ions (Li+ and Be2+) have high polarising power.
- They often form compounds with significant covalent character.
- They show diagonal relationships with magnesium and aluminium respectively.
3. What is the diagonal relationship between lithium and magnesium?
The diagonal relationship between lithium and magnesium refers to the similarity in properties of Li (Group 1) and Mg (Group 2) due to similar ionic size and charge density.
- Both form nitrides directly with nitrogen:
6Li(s) + N2(g) → 2Li3N(s)
3Mg(s) + N2(g) → Mg3N2(s) - Both form relatively insoluble carbonates.
- Their hydroxides are less soluble compared to other group members.
4. How does lithium react with water?
Lithium reacts with water to form lithium hydroxide and hydrogen gas.
- Balanced equation:
2Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g) - The reaction is less vigorous than sodium or potassium.
- Lithium hydroxide formed is a strong base.
5. Why does beryllium not react with water easily?
Beryllium does not react with water easily because it forms a protective oxide layer (BeO) on its surface.
- This oxide layer prevents further reaction.
- BeO is highly stable and has high lattice energy.
- Even with steam, beryllium shows very little reactivity compared to other Group 2 metals.
6. Are the compounds of beryllium covalent or ionic?
Most compounds of beryllium are predominantly covalent due to the high polarising power of the Be2+ ion.
- Beryllium halides like BeCl2 are covalent and polymeric in solid state.
- BeCl2 forms chains via bridging chloride atoms.
- High charge density of Be2+ distorts electron clouds, increasing covalent character.
7. What are the oxidation states of lithium and beryllium?
Lithium shows an oxidation state of +1, while beryllium shows an oxidation state of +2 in its compounds.
- Lithium forms Li+ by losing one electron.
- Beryllium forms Be2+ by losing two electrons.
- These are their most stable and common oxidation states.
8. How do lithium and beryllium react with oxygen?
Lithium forms lithium oxide (Li2O), while beryllium forms beryllium oxide (BeO) when reacting with oxygen.
- Lithium reaction:
4Li(s) + O2(g) → 2Li2O(s) - Beryllium reaction:
2Be(s) + O2(g) → 2BeO(s) - BeO is amphoteric, while Li2O is basic.
9. What is the difference between lithium hydroxide and beryllium hydroxide?
Lithium hydroxide is a strong base, whereas beryllium hydroxide is amphoteric in nature.
- LiOH dissolves in water and completely ionises.
- Be(OH)2 reacts with both acids and bases.
- With acid:
Be(OH)2(s) + 2HCl(aq) → BeCl2(aq) + 2H2O(l) - With base:
Be(OH)2(s) + 2OH-(aq) → [Be(OH)4]2-(aq)
10. What are some important uses of lithium and beryllium?
Lithium is widely used in rechargeable batteries, while beryllium is used in aerospace alloys and X-ray windows.
- Lithium: lithium-ion batteries, heat-resistant glass, psychiatric medicine (Li2CO3).
- Beryllium: lightweight alloys (Be–Cu), nuclear reactors (as moderator), X-ray tube windows.
- Both are important industrial and technological metals.
