The semimetal boron (B) and the metals aluminum (Al), gallium (Ga), indium (In) and thallium (T) are all members of the boron family, found in group 13 of the periodic table (Tl). With the ns valence electron configuration2np1, aluminum, gallium, indium, and thallium have three electrons in their outermost shell (one full s orbital and one electron in the p orbital). Elements in the boron family have oxidation states of +3 or +1. With the exception of heavier elements like Tl, which prefer the +1 oxidation state due to its stability, the +3 oxidation states are preferred; this is known as the inert pair effect.
Group 13 elements: The boron family
The first group in the p-block are the elements in group 13 of the periodic table. The boron family refers to all elements in Group 13. The periodic table is divided into four sections: s, p, d, and f. This segregation is based on the valence electron; If the valence electron is in the p subshell, it enters the p block, and so on. Boron, aluminum, gallium, indium, and thallium are group 13 elements.
The general electron configuration for Group 13 elements isns2np1
Oxidation states and inert pair effect
Group 13 elements have the following general oxidation states: +3 and +1. The tendency to form +1 ions increases as we go down the group, which is explained by the inert pair effect, which explains the absence of the s orbital during chemical bonding as a result of poor shielding of the intervening electrons. Electrons fill the d and f orbitals of elements such as indium and thallium. Because the d and f orbitals have little shielding ability, the leaking nuclear charge pulls the s orbital closer to the nucleus. As a result, the s orbital is reluctant to bond and only p electrons participate in bonding.
Covalent character of Group 13 elements
There are three reasons why Group 13 elements form covalent compounds.
- Fajan's rule can be used. The higher the covalence, the smaller the cation.
- They have extremely high ionization enthalpies, which makes it difficult for ionic compounds to form.
- Because they have higher electronegativities, the formation of compounds would not result in a greater electronegativity difference.
Reason for boron's anomalous behavior
- Boron behaves differently from other Group 13 elements for the following reasons.
- It's too small.
- It has an extremely high enthalpy of ionization.
- Due to its small size, it has high electronegativity. The absence of the d orbital of the valence shell.
Chemical properties of group 13 elements
- Group 13 reactivity to oxygen
At high temperatures, all group 13 elements react to form trioxides, M2Ö3.
4M(s) + O2(g) → 2M2Ö3(S)
Tl, in addition to the production of Tl2Ö3, can also produce Tl2O. The reactivity of Group 13 elements towards oxygen increases as you move down the group. In its crystalline form, boron does not react with oxygen. When heated, finely divided amorphous boron reacts with oxygen to form B2Ö3. Aluminum must react thermodynamically with air, but it is stable. That's because Al2Ö3forms a protective layer on the surface of the metal making it inert.
- Group 13 reactivity to acids and bases
Boron does not react with non-oxidizing acids like HCl, but at higher temperatures it does react with strong oxidizing acids like a hot concentrated mixture of H2THEN4and otorhinolaryngology3to produce boric acid.
B(s) + 3HNO3(aq) → H3BO3(aq) + 3NO2(G)
Boron is resistant to alkalis (NaOH and KOH) up to 773 K, after which it forms borates.
2B(s) + 6KOH(s) → 2K3BO3(s) + 3H2(G)
The remaining Group 13 elements react with non-oxidizing and oxidizing acids to release hydrogen gas.
- Group 13 reactivity to halogens
At high temperatures they react with halogens to form MX trihalides3. Tl, on the other hand, only produces TlF3e TlCl3.
2M(s) + 3X2(g) → 2MX3
- water reactivity
Boron does not react with water or steam, but it does react with steam at very high temperatures.
2B + 3H2O → B2Ö3+3H2
In the absence of an oxide layer, aluminum decomposes in cold water to produce hydrogen gas. In the absence of oxygen gas, gallium and indium do not react with water. In humid air, thallium produces TlOH.
4tl + 2h2O + O2→ 4TlOH
- metal reactivity
Borides are formed when boron combines with metals. The rest of the Group 13 elements are wary of combining with metals. The non-metallic nature of boron is represented in this way.
3Mg + 2B → Mg3B2
In a sufficiently high dose, all elements of the boron group can be considered toxic. Some are only toxic to animals, while others are only toxic to plants, and still others are toxic to both. For example, barley has been observed to be damaged at concentrations greater than 20 mm. Plants exhibit a wide range of boron toxicity symptoms. According to the study, they include reduced shoot and root growth, reduced cell division, photosynthesis inhibition, reduced leaf chlorophyll production, reduced root proton extrusion, reduced stomatal conductivity, and suberin and lignin deposition.
Aluminum does not pose a significant risk of toxicity in small doses, but it is mildly toxic in very large doses. Gallium is not considered toxic, although it can have some minor side effects. Although indium is non-toxic and can be handled with similar precautions as gallium, some of its compounds are mildly to moderately toxic.
Physical properties of group 13 elements
- Atomic and ionic rays
The atomic radii of Group 13 elements are smaller than those of Group 2 elements. This is due to the increase in effective nuclear charge, which causes the size of the atom to decrease. Adding a new layer decreases the atomic and ionic radii in the group. However, there is a difference when switching from aluminum (143 pm) to gallium (135 pm). This is due to the poor gallium shielding of the intermediate d orbitals, resulting in a smaller size than aluminum.
Bor < Aluminum > Gallium < Indium < Thallium
- ionization energy
Ionization enthalpy values do not decrease uniformly across the group. As expected, the enthalpy of ionization increases from boron to aluminum. However, the ionization enthalpy increases slightly from aluminum to gallium. Thallium has a higher enthalpy of first ionization than aluminum. This pattern is caused by poor shielding of the d and f orbitals.
Electronegativity decreases from B to Al and then increases slightly from Aluminum to Tl. This is due to ineffective shielding of the intermediate d and f orbitals.
The expected trend should be the reversal of electronegativity. The metallic character increases slightly from B to Al and then decreases slightly from Al to Tl. This is due to the extremely high enthalpy of ionization of Group 13. Also, the larger the ion, the lower its enthalpy of ionization. Therefore, aluminum is the most metallic. This can be explained using standard reduction potentials.
- acid-base properties
The acidic character of Group 13 elements decreases as they move down the group, while the basic character increases.
Question 1: What is Fajan's rule?
Fajans' rule determines whether a chemical bond is covalent or ionic.
Question 2: Why does aluminum have a lower density than boron?
Density increases as you move from boron to thallium. In contrast, boron and aluminum have relatively low values. This is because they have lower atomic masses than gallium, indium, and thallium.
Question 3: How are the properties of aluminum similar to those of boron?
Boron and aluminum are members of the same elemental group (13th group). Elements with similar chemical properties are grouped together on the modern periodic table. Boron and aluminum have three valence electrons and exhibit three valences.
Question 4: Name an application of the boron family.
Boron is found in a wide variety of industrial applications and new ones are being discovered all the time. Fiberglass is a common material. The borosilicate glass market has also grown rapidly; One of the family's differentials is the greater resistance to thermal expansion in relation to common glass.
Ceramics is another booming commercial application for boron and its derivatives. Many boron compounds, particularly the oxides, have valuable and unique properties that have led to their replacement by less useful materials. The insulating properties of boron can be found in vases, pots, pot handles and ceramic dishes.
Question 5: What is Borax?
Borax is a refined compound and a mineral with many uses. This mineral exists as colorless, fluffy white crystals that may occasionally be tinged yellow, green, or brown.
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