Periodic Table Trends (PDF)

# Introduction Periodic table is a systematic arrangement of elements based on their atomic numbers, electronic configuration and properties. The long form of periodic table consists of seven horizontal rows known as periods and eighteen vertical columns known as groups. There are two types of group...

# Introduction Periodic table is a systematic arrangement of elements based on their atomic numbers, electronic configuration and properties. The long form of periodic table consists of seven horizontal rows known as periods and eighteen vertical columns known as groups. There are two types of groups in the periodic table. - Sub group A, referred to as representative elements. - Sub group B is known as transition elements. The block in the periodic table refers to specific sections based on the type of orbitals being filled by valence electrons. There are four blocks in the modern periodic table named as: - s-block - p-block - d-block - f-block ## The Blocks ### s-block The elements of s-block are located on extreme left in the periodic table. It consists of groups IA and IIA. The valence shell electronic configuration of the elements of this block is $ns^1$ for alkali metals and $ns^2$ for alkaline earth metals. ### p-block The p-block is found on extreme right of the periodic table and includes groups IIIA to VIIIA. Elements belong to this block possess a valence shell electronic configuration of $ns^2$, $np^1$ to $ns^2$, $np^6$. ### d-block The d-block elements are located in the middle of the periodic table and cover up all sub group B. The general valence shell electronic configuration of these elements is $ns^2$, $(n-1)d^1$ to $ns^2$, $(n-1)d^{10}$. ### f-block The f-block elements are located below the main body of periodic table and exist in two horizontal series of fourteen elements each, generally known as lanthanides and actinides. The valence configuration of f-block elements is $ns^{1,2}$, $(n-2)f^1$ to $ns^{1,2}$, $(n-2)f^{14}$. The position of each element in a particular group, period and block can be identified by its electronic configuration. - The principal quantum number (n) of the valence electrons represents the period of an element. - The group of an element is predicted from the number of electrons in the valence shell. For example, the atomic number of sulphur is 16 ($1s^2$, $2s^2$, $2p^6$, $3s^2$, $3p^4$), therefore it is predicted that sulphur belongs to the third period and VIA group. Another feature of the long form of periodic table is the regular changes in the physical properties of elements downward in the group and along with the period except ignoring anomalies in certain places. # General Group Trends of Representative Elements Elements in the long form of periodic table are arranged according to their increasing atomic number and electronic configuration in such a manner that their general properties are correlated to each other. They exhibit a regular trend in properties within each group, with some exceptions or anomalies occurring in specific positions. # Atomic Radii "Atomic radius is the distance between the nucleus of an atom to its outermost electron shell". ## Group Trends ### IA and IIA Groups Elements of group IA are termed as alkali metals. They possess the largest atomic radii in their respective periods. However the atomic radii increase regularly from lithium to francium. It is because the number of energy levels occupied by electrons increases, resulting in an increase in the distance between the nucleus and the outermost electronic shell. Similarly, the same trend applies to the elements of group IIA (Be to Ra). That means beryllium is the smallest alkaline earth metal (IIA) and barium is the largest, as shown in Table 1.1. | Alkali Metals (Group IA) | Atomic Radii (pm) | Alkaline Earth Metals (Group IIA) | Atomic Radii (pm) | |---|---|---|---| | Li | 152 | Be | 112 | | Na | 186 | Mg | 145 | | K | 227 | Ca | 194 | | Rb | 248 | Sr | 219 | | Cs | 265 | Ba | 253 | | Fr | 348 | Ra | 215 | ### IIIA Group Atomic radii of the elements of Boron family (Group IIIA) generally increase down the group (from boron to thallium). However, there is an exception to the trend between aluminum and gallium. Gallium has slightly smaller atomic radii than aluminum despite being located below it in the group. It is because of poor shielding effect caused by electrons of d-orbitals. ### IVA to VIIIA Groups The atomic radii of elements of Group IVA to Group VIIIA follow the similar group trend, increasing regularly from top to bottom within the group as shown in Table 1.2. The same reason for this trend is discussed as in the group trend of alkali metals. | Group | Atomic Radii (pm) | |---|---| | IIIA | | | B | 85 | | Al | 143 | | Ga | 135 | | In | 167 | | Tl | 170 | | IVA | | | C | 77 | | Si | 118 | | Ge | 122 | | Sn | 140 | | Pb | 146 | | VA | | | N | 75 | | P | 110 | | As | 120 | | Sb | 140 | | Bi | 150 | | VIA | | | O | 73 | | S | 103 | | Se | 119 | | Te | 142 | | Po | 168 | | VIIA | | | F | 72 | | Cl | 100 | | Br | 114 | | I | 133 | | At | 140 | | VIIIA | | | Ne | 71 | | Ar | 98 | | Kr | 112 | | Xe | 131 | | Rn | 141 | # Ionization Energy "It is the energy needed to remove an electron from a neutral atom in the gas phase". ## Group Trends ### IA and IIA Groups The ionization energy of alkali metals (Group IA) and alkaline earth metals (Group IIA) decreases as we move down the group. This is because the outermost electrons of these elements are located farther away from the nucleus as we go from top to bottom, leading to weaker attractive forces between the electrons and the nucleus. As a result, it requires less energy to remove the outer shell electrons from the atom, that is why the ionization energy decreases. ### IIIA Group The ionization energy (IE) trend in group IIIA elements has irregularities as we move down the group. Two exceptions highlight this irregularity. - Firstly, gallium (Ga) has a higher ionization energy than aluminum (Al). - Secondly, thallium (Tl) exhibits a higher ionization energy than indium (In). These irregularities occur due to insufficient shielding of the nuclear charge in gallium by 3d electrons and in thallium by 4f electrons. ### IVA Group The ionization energy of group IVA elements generally decreases from top to bottom in the group. However, there are irregularities observed between Tin (Sn) and Lead (Pb). This is because both tin and lead have nearly the same atomic radii, which is a result of the lanthanide contraction. Due to this, the attraction between the nucleus and the outer electrons becomes stronger and requires more energy to remove these electrons. ### VA, VIA, VIIA and VIIIA Groups The ionization energy of the remaining groups of representative elements (group VA, VIA, VIIA, VIIIA) follows a regular pattern. It decreases progressively from top to bottom as the atomic radii increase, as shown in Table 1.3. | Group | First ionization energies of representative elements in KJ/mol | |---|---| | IA | | | Li | 520 | | Na | 490 | | K | 420 | | Rb | 400 | | Cs | 380 | | IIA | | | Be | 900 | | Mg | 730 | | Ca | 590 | | Sr | 550 | | Ba | 500 | | IIIA | | | B | 800 | | Al | 577 | | Ga | 580 | | In | 560 | | Tl | 590 | | IVA | | | C | 1090 | | Si | 780 | | Ge | 762 | | Sn | 700 | | Pb | 710 | | VA | | | N | 1400 | | P | 1060 | | As | 960 | | Sb | 830 | | Bi | 800 | | VIA | | | O | 1310 | | S | 1001 | | Se | 950 | | Te | 870 | | Po | 810 | | VIIA | | | F | 1680 | | Cl | 1250 | | Br | 1140 | | I | 1010 | | At | 920 | | VIIIA | | | Ne | 2080 | | Ar | 1520 | | Kr | 1350 | | Xe | 1170 | | Rn | 1030 | # Electronegativity (EN) "It is the measure of the tendency of an atom to attract the shared pair of electrons towards itself when it is involved in a covalent bond”. ## Group Trends ### IA and IIA Groups The electronegativity (EN) of alkali metals (Group IA) and alkaline earth metals (Group IIA) follows a regular decreasing trend from top to bottom. This trend can be explained by the regular increase in atomic radii as we move down the group. The larger atomic size results in a decreasing tendency for the atom to attract the shared pair of electrons towards itself. ### IIIA Group The electronegativity (EN) of group III elements initially decreases from Boron (B) to Aluminum (Al) and then increases from gallium (Ga) to tellurium (Te). This irregular increase in EN can be attributed to the poor shielding effect of the electrons in the d-orbital and f-orbitals, respectively. ### IVA, VA, VIA and VIIA Groups The electronegativity of groups IVA, VA, VIA, and VIIA decreases regularly from top to bottom. This trend can be explained by the same reason as discussed for alkali metals as shown in Table 1.4. | Group | Electronegativity value of representative elements | |---|---| | IA | | | Li | 1.0 | | Na | 0.9 | | K | 0.8 | | Rb | 0.8 | | Cs | 0.7 | | IIA | | | Be | 1.5 | | Mg | 1.2 | | Ca | 1.0 | | Sr | 0.95 | | Ba | 0.9 | | IIIA | | | B | 2.0 | | Al | 1.5 | | Ga | 1.7 | | In | 1.7 | | Tl | 1.8 | | IVA | | | C | 2.5 | | Si | 1.9 | | Ge | 1.8 | | Sn | 1.8 | | Pb | 1.8 | | VA | | | N | 3.0 | | P | 2.1 | | As | 2.0 | | Sb | 1.9 | | Bi | 1.9 | | VIA | | | O | 3.5 | | S | 2.5 | | Se | 2.4 | | Te | 2.1 | | Po | 2.0 | | VIIA | | | F | 4.0 | | Cl | 3.0 | | Br | 2.8 | | I | 2.5 | | At | 2.2 | # Electrical Conductivity "Electrical conductivity is the measurement of a material's capability to conduct electric current". It is a measure of how easily electric charges, such as electrons, can flow through a substance. Materials with high electrical conductivity allow electric current to pass through them easily, while materials with low electrical conductivity hinder the flow of electric charges. ## Group Trends The electrical conductivity of representative elements can vary widely. - Alkali metals and alkaline earth metals generally exhibit high electrical conductivity due to their ability to easily transfer electrons. - Group IIIA elements display moderate electrical conductivity, while elements in Group IVA can have variable conductivity ranging from poor (e.g., carbon and lead) to moderate (e.g., silicon and tin). - Group VA, VIA, and VIIA elements typically have poor electrical conductivity. - Noble gases, on the other hand, have extremely low electrical conductivity as shown in Table 1.5. | Group Number | Trend of Electrical Conductivity | |---|---| | Group I and IIA | High electrical conductivity | | Group IIIA | Moderate electrical conductivity | | Group IVA | Variable electrical conductivity (Carbon: poor, Silicon: moderate, Germanium: moderate, Tin: moderate, Lead: poor) | | Group VA | Moderate electrical conductivity | | Group VIA | Poor electrical conductivity | | Group VIIA (Halogens) | Poor electrical conductivity | | Group VIIIA (Noble gases) | Extremely low electrical conductivity | # Oxidation State "An oxidation number is a value assigned to an element in a chemical compound or combined state." The oxidation states of representative elements depend on their position in a particular group of periodic table. Some oxidation states are shown in Table 1.6. | Group | Elements | Oxidation States | |---|---|---| | IA (Alkali Metals) | Li, Na, K, Rb, Cs | +1 | | IIA (Alkaline Earth Metals) | Be, Mg, Ca, Sr, Ba | +2 | | IIIA | B, Al, Ga, In, Tl | +3 | | IVA | C, Si, Ge, Sn, Pb | -4, -2, +2, +4 | | VA | N, P, As, Sb, Bi | -3, -2, +3, +5 | | VIA | O, S, Se, Te, Po | -2, +2, +4, +6 | | VIIA (Halogens) | F, Cl, Br, I, At | -1, +1, +3, +5, +7 | | VIIIA (Noble Gases) | He, Ne, Ar, Kr, Xe, Rn | 0 | # Melting and Boiling Point The melting and boiling points of representative elements can vary widely across the periodic table. - Alkali metals have low melting and boiling points due to weak metallic bonding, while alkaline earth metals have higher melting and boiling points due to stronger metallic bonding as shown in Table 1.7. - Moving across the p-block elements, the melting and boiling points generally increase gradually. However, there are exceptions in groups IVA and VA. - Carbon has a high melting point due to strong covalent bonds, while nitrogen has low melting and boiling points because it exists as diatomic molecules with weak intermolecular forces. - Halogens have low melting and boiling points due to weak intermolecular forces, and noble gases have extremely low melting and boiling points due to weak interatomic forces. The melting and boiling points of representative elements reflect the different bonding types and intermolecular forces within each group, resulting in a wide range of physical properties. | Group | Melting point of representative element in °C | |---|---| | IA | | | Li | 180 | | Na | 97.8 | | K | 63.7 | | Rb | 39.0 | | Cs | 28.6 | | IIA | | | Be | 1278 | | Mg | 651 | | Ca | 843 | | Sr | 769 | | Ba | 725 | | IIIA | | | B | 2300 | | Al | 658 | | Ga | 297 | | In | 155 | | Tl | 303 | | IVA | | | C | 3700 | | Si | 1410 | | Ge | 937 | | Sn | 232 | | Pb | 327 | | VA | | | N | -210 | | P | 34 | | As | 814 | | Sb | 630 | | Bi | 271 | | VIA | | | O | -219 | | S | 119 | | Se | 217 | | Te | 450 | | Po | - | | VIIA | | | F | -220 | | Cl | -102 | | Br | -7.2 | | I | 114 | | At | - | | VIIIA | | | Ne | -248 | | Ar | -186 | | Kr | -157 | | Xe | -112 | | Rn | -71 | # Unique behavior of Beryllium in group IIA Beryllium differs markedly from its other members because of its smaller atomic radii and high electronegativity. Some unique characteristics shown by beryllium in comparison to other elements of group IIA are given as: - Beryllium is harder and more rigid than other members of group IIA. - Beryllium has relatively low density and high melting point compared with other group members. - Beryllium exhibits chemical stability due to the formation of protective oxide layer on its surface which prevents further oxidation and corrosion. - Beryllium has tendency to form covalent bonds with other elements due to its smaller atomic size while other members of the group form ionic bonds. # Reactions of Representative Elements ## s-block elements Alkali metals (group IA) and alkaline earth metals (group IIA) are highly reactive because they can easily lose their valence electrons due to low ionization energy (IE). Some common reactions of the elements of group IA and IIA are given as. ### With Oxygen Alkali metals rapidly react with oxygen to produce oxides. Lithium forms normal oxide (oxidation state of oxygen is -2), sodium forms peroxide (oxidation state of oxygen is -1) in excess of air while the rest of the elements of group IA form superoxides (oxidation state of oxygen is - ). - $4Li(s) + O_2(g) \rightarrow 2Li_2O(s)$ (Normal oxide) - $2Na(s) + O_2(g) \rightarrow Na_2O_2(s)$ (Per oxide) - $K(s) + O_2(g) \rightarrow KO_2(s)$ (Super oxide) - $Rb(s) + O_2(g) \rightarrow RbO_2(s)$ (Super oxide) - $Cs(s) + O_2(g) \rightarrow CSO_2(s)$ (Super oxide) The reaction of alkaline earth metals with oxygen takes place at high temperature. However, on oxidation, beryllium, magnesium and calcium form normal oxides while strontium and barium form peroxides. - $2M + O_2 \rightarrow 2MO$ (Where M = Be, Mg, Ca) - $M + O_2 \rightarrow MO_2$ (Where M = Sr, Ba) ### With Water Alkali metals react with water to produce metal hydroxides with the liberation of hydrogen gas. The intensity of reaction increases from lithium to cesium, until a violent reaction is observed often accompanied by an explosion when cesium is put into water. - $2M(s) + 2H_2O(l) \rightarrow 2MOH(aq) + H_2(g) \uparrow$ (Where M = Li, Na, K, Rb, Cs). Among alkaline earth metals, beryllium does not react with either cold or steam, but magnesium reacts with steam. The reason is that these two elements form a stable oxide layer that acts as a barrier preventing direct contact between water and metal. The rest of the members of this group react with water easily and form hydroxides. - $M(s) + 2H_2O(l) \rightarrow M(OH)_2(aq) + H_2 \uparrow$ (Where M = Mg, Ca, Sr and Ba). ### With Halogens Alkali metals react vigorously with halogens to form metal halides. The reaction involves the transfer of electron from an alkali metal to a halogen. - $2M(s) + X_2(g) \rightarrow 2MX(s)$ (Where M = Li, Na, K, Rb, Cs) Alkaline earth metals also react with halogens although to a lesser extent when compared with alkali metals. - $M(s) + X_2(g) \rightarrow MX_2(s)$ (Where M = Be, Mg, Ca, Sr, Ba) ### With Nitrogen Nitrides are formed when both alkali metals and alkaline earth metals react with nitrogen. The general formula for the nitrides of alkali metals is $M_3N$ and for the nitrides of alkaline earth metals is the formula $M_3N_2$. - $6M(s) + N_2(g) \rightarrow 2M_3N(s)$ (M = Li, Na, K, Rb, Cs) - $3M(s) + N_2(g) \rightarrow M_3N_2(s)$ (M = Be, Mg, Ca, Sr, Ba) ### With Hydrogen Alkali and alkaline earth metals react with hydrogen at different temperatures to produce ionic hydrides. - $2M(s) + H_2(g) \rightarrow 2MH(s)$ (M = Li, Na, K, Rb, Cs) - $M(s) + H_2(g) \rightarrow MH_2(s)$ (M = Ca, Sr, Ba) ### With Alcohols Elements of group IA react vigorously with alcohols to form metal alkoxide with the liberation of hydrogen gas. - $2M(s) + 2C_2H_5OH(aq) \rightarrow 2C_2H_5OM(aq) + H_2(g)$ (M = Li, Na, K, Rb, Cs) Alkaline earth metals have a very limited reactivity with alcohols. ### With Acids Alkali metals react vigorously with acids to produce salt with the liberation of hydrogen gas. This reaction is highly exothermic and violent. - $2M(s) + 2HCl(aq) \rightarrow 2MCl(s) + H_2(g)$ (Where M = Li, Na, K, Rb, Cs) Alkaline earth metals can react with acids but their reactivity is generally lower compared to alkali metals. # Flame Test for S-Block Elements "Flame test is a qualitative method used to identify the presence of alkali metals based on their characteristic flame colours". When an alkali metal or its compound burn in flame, the electron in the lower energy orbital jumps to higher energy orbital due to the absorption of energy from the flame. This electron upon returning to lower energy orbital, releases energy in the form of light of a specific colour which can be observed as a colour flame. | Elements | Flame Colour | |---|---| | Lithium | Red | | Sodium | Yellow | | Potassium | Violet | | Rubidium | Red Violet | | Cesium | Blue Violet | | Beryllium | No characteristic flame colour | | Magnesium | Silver white | | Calcium | Orange red | | Strontium | Deep Red | | Barium | Pale Green | # Chemistry of Important Compounds of S-Block Elements There are various naturally occurring compounds of alkali and alkaline earth metals found in the earth's crust in the form of minerals and ores. However, many useful compounds of s-block elements are synthesized in industries, such as caustic soda, soda ash, bleaching powder etc. ## Sodium Hydroxide (NaOH) Sodium hydroxide is a highly versatile and widely used chemical compound. It is commonly known as caustic soda due to its ability to cause burns and damage tissues severely. Caustic soda is manufactured by an electrolytic process in a specially designed cell known as Castner Kellner cell. The cell consists of an upper rectangular vessel and a lower pipe like portion. In the upper part, there are titanium blocks which are submerged in an aqueous solution of sodium chloride acting as an anode. The lower section is filled with mercury which circulates constantly with the help of a pump and serves as cathode. The upper part of the cell is connected to the lower part by a graphite made chamber known as denuder where the separation of sodium from amalgam takes place. The aqueous solution of sodium chloride in the upper portion consists of mainly sodium ions (Na+) and chloride ions (Cl¯). On passing electricity through the cell, all Cl- ions migrate toward titanium anode where they get oxidized. The chlorine gas liberated in this electrolytic process is collected as a by-product. - $2Cl(aq) \rightarrow Cl_2(g) + 2ē$ (Oxidation) OH ions of water which are in very low quantities, are also oxidized on titanium anode. - $40H(aq) \rightarrow 2H_2O(l) + O_2(g)$ (Reduction) Sodium ions on the other hand discharge over mercury surface where an amalgam of Na/Hg (alloy) is formed. - $2Na (aq) + 2ē \rightarrow 2Na(aq)$ - $Na(1) + Hg(l) \rightarrow Na/Hg(e)$ Amalgam is then sent to denuder where sodium reacts with water to form sodium hydroxide. - $2Na/Hg + 2H_2O(l) \rightarrow 2NaOH(aq) + H_2(g) + Hg(l)$ The mercury is recycled to dissolve more sodium and the sodium hydroxide is collected for marketing. Compared with other processes for the preparation of caustic soda, the Castner Kellner process is more preferable because the two products of the process, sodium hydroxide and chlorine are obtained in separate portions of the cell, which prevents them to react with each other. However, one disadvantage of the process is that, in spite of strict control some mercury vapours escape from the factory. This mercury contaminates seawater. As a result mercury becomes part of tissues of marine animals and plants and thus pollutes the food chain. ## Physical Properties - **State:** It is a solid at room temperature, typically appearing as white pellets, flakes, or granules. - **Odor:** It is odorless. - **Melting Point:** Its melting point is approximately 318 °C (604 °F). At this temperature, it melts and forms a liquid. - **Solubility:** It is highly soluble in water. - **Density:** The density of NaOH depends on its concentration and temperature. For a 50% concentration at room temperature, the density is approximately 1.52 g/cm³. - **Corrosiveness:** It is highly corrosive and can cause burns and irritation to the skin, eyes, and respiratory system. ## Chemical Properties ### Reaction with acids Being a strong base, it reacts with all acids to produce sodium salt and water. - $NaOH(aq) + HCl(aq) \rightarrow NaCl(aq) + H_2O(l)$ - $2NaOH(aq) + H_2SO_4(aq) \rightarrow Na_2SO_4(aq) + 2H_2O(l)$ ### Reaction with Ferric Chloride On reaction with aqueous ferric chloride, it gives brown ppt of ferric hydroxide. - $3NaOH(aq) + FeCl_3(aq) \rightarrow Fe(OH)_3(s) + 3NaCl(aq)$ ### Reaction with Aluminum and Zinc Caustic soda can react with aluminum and zinc to form aluminate and zincate salts. - $2NaOH(aq) + 2Al(s) + 2H_2O(l) \rightarrow 2NaAlO_2(s) + 3H_2(g)$ - $2NaOH(aq) + Zn(s) \rightarrow Na_2ZnO_2(s) + H_2(g)$ ### Reaction with Chlorine The reaction of hot aqueous sodium hydroxide with chlorine gas gives sodium chloride and sodium chlorate. - $6NaOH(aq) + 3Cl_2 (g) \rightarrow NaClO_3(aq) + 5NaCl(aq) + 3H_2O(l)$ ## Uses of Sodium Hydroxide - It is a key ingredient in the production of detergents and soaps. - It is utilized in the production of bleach, such as chlorine bleach, which is commonly used as a disinfectant and stain remover. - Its strong alkaline nature makes it effective for unclogging drains and pipes by breaking down organic matter. - It is used to remove heavy metals and adjust pH levels in water, ensuring safe and clean drinking water. - It is used as a food preservative to prevent bacterial and mold growth, enhancing the shelf life of certain food products. - It is utilized in the canning process to remove the outer skin of fruits and vegetables, ensuring food safety and quality. - It plays a role in the paper making industry, where it is used for pulping wood fibers and paper recycling processes. ## Bleaching Powder(CaOCl2) Bleaching powder, also known as calcium hypochloride (CaOCl2), is a chemical compound widely used as a bleaching agent and disinfectant. Commercially, it is prepared by Hasenclever Process, as shown in figure 1.2. Dry slaked lime is fed into the Hasenclever plant from the most upper cylinder. The slaked lime is moved forward by revolving blades of rotating shaft. Chlorine gas is passed from the lower cylinder which rises upto upper cylinder and reacts with slaked lime to form bleaching powder. - $Ca(OH)_2(aq) + Cl_2(aq) \rightarrow CaOCl_2(s) + H_2O(l)$ ## Physical Properties of Bleaching Powder - Bleaching powder has a dirty white appearance. - It has a distinct chlorine odour. - It is soluble in water. ## Chemical Properties of Bleaching Powder ### Reaction with Water Bleaching powder when dissolves in water, it produces calcium hydroxide and hypochlorous acid (HOCl). Hypochlorous acid is a weak acid and commonly used for bleaching and sanitizing. - $CaOCl_2(s) + H_2O (1) \rightarrow Ca(OH)_2(aq) + 2HOCl(aq)$ ### Reaction with Acids The reaction of bleaching powder with hydrochloric acid produces calcium chloride and chlorine gas. - $CaOCl_2(s) + 2HCl(aq) \rightarrow CaCl_2(s) + 2H_2O(l) + Cl_2(g)$ ## Uses of Bleaching Powder - It is used for sterilization of water. - It is used for bleaching of cotton, linen and paper. - It is used for the preparation of chlorine gas and chloroform. # Reactions of p-Block Elements Elements of group IIIA to VIIA in the periodic table exhibit diverse chemical behavior. They can participate in various types of chemical reactions based on their unique properties. Some important chemical reactions involving p-block elements are given below. ## With Oxygen The reactions of p-block elements with oxygen produce either normal oxides or in some cases peroxides. Elements of group IIIA react with oxygen to produce oxides of the formula $M_2O_3$. - $4B(s) + 3O_2(g) \rightarrow 2B_2O_3(s)$ - $4Al(s) + 3O_2(g) \rightarrow 2Al_2O_3(s)$ In group IVA, carbon forms carbon monoxide and carbon dioxide when it reacts with oxygen while silicon form only one stable silicon oxide($SiO_2$). - $C(s) + O_2(g) \rightarrow CO_2(g)$ - $2C(s) + O_2(g) \rightarrow 2CO (g)$ (above 900°C) - $Si(s) + O_2(g) \rightarrow SiO_2(s)$ In group VA, nitrogen forms NO, $N_2O$ and $NO_2$ when reacts with oxygen depending upon the conditions applied. Phosphorus may form $P_2O_3$ in limited supply of oxygen whereas $P_2O_5$ in excess of oxygen. - $N_2(g) + O_2(g) \rightarrow 2NO(g)$ (High temp.) - $2N_2(g) + O_2(g) \rightarrow 2N_2O(g)$ (Catalyst) - $4P(s) +3O_2(g) \rightarrow 2P_2O_3(s)$ (Limited oxygen) - $4P(s) +5O_2(g) \rightarrow 2P_2O_5(s)$ (Excess oxygen) In group VIA, sulphur oxidized in air to give sulphur dioxide. - $S(s) + O_2(g) \rightarrow SO_2(g)$ Halogens can also react with oxygen however their oxides are mostly highly reactive. For example the oxide of fluorine is a highly reactive yellow gas. The oxides of halogens are very unstable. - $2F_2(g) + O_2(g) \rightarrow 20F_2(g)$ ## With Water The reaction of p-block elements with water depends on the nature of element and the group to which it belongs. - Aluminum reacts with water but the reaction is slow due to the presence of a thin oxide film on its surface. - $2Al(s) + 6H_2O(1) \rightarrow 2Al(OH)_3(s) + 3H_2(g)$ Silicon reacts with steam and forms slicondioxide. - $Si(s) + 2H_2O(g) \rightarrow SiO_2(s) + 2H_2(g)$ Phosphorus reacts vigorously with water to produce phosphoric acid and phosphine. - $2P_4(s) + 12H_2O(1) \rightarrow 3H_3PO_4(aq) + 5PH_3(g)$ (high temp.) Sulphur reacts if it is heated to a high temperature. - $S(s) + 2H_2O(1) \rightarrow SO_2(g) + 2H_2(g)$ Halogens such as chlorine and bromine react with water to form a mixture of two acids. - $Cl_2(g) + H_2O(1) \rightarrow HCl(aq) + HOCl(aq)$ - $Br_2(1) + H_2O(1) \rightarrow HBr(aq) + HOBr(aq)$ ## With Halogens Majority of p-block elements have the capability to react with halogens, resulting in the formation of binary compounds. - $2Al(s) + 3Cl_2(g) \rightarrow 2AlCl_3(s)$ - $C(s) + 2Cl_2(g) \rightarrow CCl_4(l)$ - $N_2(g) + 3Cl_2(g) \rightarrow 2NCl_3(g)$ - $O_2(g) + 2F_2(g) \rightarrow 20F_2(g)$ ## With Nitrogen The reaction of p-block elements with nitrogen can vary depending on the specific element and the reaction conditions. For example