What are the key properties and reactivity of the acylium ion?

The acylium ion is a positively charged molecule with a carbon atom double bonded to an oxygen atom. It is highly reactive due to its electron deficiency, making it prone to nucleophilic attack. The key properties of the acylium ion include its electrophilic nature, ability to form stable complexes with nucleophiles, and participation in various organic reactions such as acylation and Friedel-Crafts reactions.