O O− \\\\ / N+ | O−A nitrate salt forms if a positively charged ion attaches to one of the negatively charged oxygen atoms of the nitrate ion.
Nitrates are also oxidizing agentss. When mixed with hydrocarbons or carbohydrates, nitrates can form a flammable or even explosive mixture. For example, potassium nitrate is the oxidizing ingredient in black gunpowder.
In Medicine, Nitrates such as nitroglycerin and isosorbide mono- and di- nitrates are particularly useful for prevention and treatment of angina pectoris. However they can cause a dangerous reaction if taken within 24 hrs of taking Viagra or sildenafil citrate.
Nitrates covered in Wikipedia include:nitrous acid.