Iodine crystal

A solid, grey substance which sublimates when heated. Its solution in alcohol is called ´tincture of iodine´, it is a disinfectant.

Beryllium dichloride (BeCl₂)

Used in the production of beryllium and as a catalyst.

Comparison of hydrogen halides

Atoms within hydrogen halides are bound by covalent bonds, forming polar molecules.

Hydronium ion (H₃O⁺)

The presence of hydronium ions relative to hydroxide ions determines a solution´s pH.

Bromine (Br₂)

One of the halogens, it may cause skin irritation.

Fluorine (F₂)

The lightest halogen, a pale yellow-green, toxic gas, extremely reactive. Its best known compound is teflon.

Boron trifluoride (BF₃)

Colourless, heavier-than-air gas with a pungent odour. It forms white fumes in moist air.

Phosphate ion (PO₄³⁻)

A compound ion formed when a phosphoric acid molecule releases a proton.

Silver nitrate (AgNO₃)

One of the raw materials of traditional photography.

Nitrate ion (NO₃⁻)

A compound ion, the main source of nitrogen for plants.

Sulphate ion (SO₄²⁻)

A compound ion produced when sulphuric acid releases protons.

Hydroxide ion (OH⁻)

A compound ion formed when a water molecule releases a proton.

Hydrogen (H₂)

Colourless, odourless, lighter-than-air gas. The most common chemical element in the universe.

Water (H₂O)

Water is a very stable compound of hydrogen and oxygen, vital for all known forms of life. In nature it occurs in liquid, solid and gaseous state.

Ammonia (NH₃)

Ammonia is a colourless gas with a characteristic pungent smell. Its solution in water is called ammonium hydroxide or household ammonia.

Sulphur (S₈)

An odourless, yellow, solid substance, the 16th most common in the Earth´s crust. One of the best known sulphur compounds is pyrite, also known as ´fool´s...

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