Читать книгу Foundations of Chemistry - Philippa B. Cranwell - Страница 90

Calcium fluoride contains two elements: calcium and fluorine. Calcium is a metal on the left of the periodic table, in Group 2. Fluorine is a non‐metal and resides in Group 7 (Group 17). Because we have a metal and a non‐metal in the compound, the type of bonding present is ionic. Therefore, the main interaction between atoms will be electrostatic: i.e. a positive ion with a negative ion.

When asked a question about the type of bonding in a compound, the first thing to check is the types of elements that are bonded and whether they are metals or non‐metals.

As stated earlier, calcium is in Group 2. Therefore, to gain a full outer shell, it needs to lose two electrons. In doing this, it will have a 2+ charge.

Fluorine is in Group 7. Therefore, to gain a full outer shell, it needs to gain one electron. By doing this, it has a negative charge. To balance the two electrons given up by calcium, there need to be two fluorine atoms present that can each take one electron.