Page 2: Chromium and Manganese

This page delves into the chemistry of chromium and manganese, focusing on their various oxidation states and important reactions.

Chromium exhibits multiple oxidation states, with +3 and +6 being the most common. Chromium$III$ compounds, such as Cr₂O₃ and Cr$OH$₃, display amphoteric properties.

Highlight: Chromium$VI$ compounds, like chromates $CrO₄²⁻$ and dichromates $Cr₂O₇²⁻$, are strong oxidizing agents.

The page outlines several key reactions involving chromium compounds:

1. Formation of chromium$III$ hydroxide
2. Amphoteric behavior of Cr$OH$₃
3. Thermal decomposition of ammonium dichromate

Example: $NH₄$₂Cr₂O₇ → Cr₂O₃ + N₂ + 4H₂O $decomposition of ammonium dichromate$

Manganese is presented with its various oxidation states, ranging from +2 to +7. The stability and acid-base properties of manganese compounds vary with the oxidation state.

Vocabulary: Redox - A type of chemical reaction involving the transfer of electrons between species.

Important reactions of manganese compounds are discussed, including:

1. Disproportionation of potassium permanganate
2. Amphoteric behavior of MnO₂
3. Reaction of MnO₂ with hydrogen peroxide

Example: 2KMnO₄ → K₂MnO₄ + MnO₂ + O₂ $disproportionation of potassium permanganate$

Page 3: Iron, Hydrogen, Aluminum, and Silicon

This page covers the chemistry of iron, hydrogen, aluminum, and silicon, focusing on their properties, reactions, and applications.

Iron undergoes passivation when exposed to concentrated nitric or sulfuric acid, forming a protective oxide layer. The page outlines important reactions of iron, including its reaction with hydrochloric acid and chlorine.

Vocabulary: Passivation - The formation of a protective layer on a metal's surface, preventing further corrosion.

Hydrogen production methods are discussed, including:

1. Reaction of active metals with acids
2. Steam reforming of methane
3. Water-gas shift reaction
4. Electrolysis of water or brine

Example: CH₄ + H₂O → CO + 3H₂ $steam reforming of methane$

Aluminum's passivation and its amphoteric nature are explored. The aluminothermic reaction, used in welding, is also mentioned.

Highlight: Aluminum forms a protective oxide layer $Al₂O₃$ when exposed to air, preventing further corrosion.

Silicon, an important element in the earth's crust, is discussed in terms of its inorganic compounds. Silicon dioxide $SiO₂$ exhibits weak acidic properties and reacts with hydrofluoric acid.

Example: SiO₂ + 4HF → SiF₄ + 2H₂O $reaction of silicon dioxide with hydrofluoric acid$

The page concludes with a brief mention of silicic acid $H₂SiO₃$ and its properties.

Page 1: Alkali Metals and Alkaline Earth Metals

This page focuses on the properties and reactions of alkali metals $lithium, sodium, potassium$ and alkaline earth metals $beryllium, calcium, strontium, barium$. It covers their reactions with oxygen, formation of hydroxides, and characteristic tests.

Highlight: Alkali metals are highly reactive, forming oxides, peroxides, and superoxides when exposed to oxygen.

The Blok s elements, particularly lithium, sodium, and potassium, demonstrate increasing reactivity down the group. Their reactions with oxygen produce different products:

• Lithium forms lithium oxide $Li₂O$
• Sodium forms sodium peroxide $Na₂O₂$
• Potassium forms potassium superoxide $KO₂$

Example: 2Na + O₂ → Na₂O₂ $sodium peroxide formation$

The page also discusses the Trommer's test, which involves the reaction of copper$II$ hydroxide with reducing sugars, resulting in a color change.

Vocabulary: Hygroscopic - A substance that readily absorbs moisture from the air.

Alkaline earth metals, including beryllium, calcium, strontium, and barium, are discussed in terms of their oxides and hydroxides. Beryllium oxide and hydroxide exhibit amphoteric properties, while the others are basic.

Definition: Amphoteric - A substance that can act as both an acid and a base.

The chemical activity of alkaline earth metals increases down the group, with calcium carbonate being a significant compound found in limestone.

Example: CaCO₃ + CO₂ + H₂O → Ca$HCO₃$₂ $formation of calcium bicarbonate in hard water$