Metals Help (page 3)

By — McGraw-Hill Professional
Updated on Aug 28, 2011

Naming Metals And Non-metals

In general, metals form positive ions (cations), while non-metals form negative ions (anions). Noble gases, remember, are happy as they are and do not form cations or anions.

When a metal cation and a non-metal anion form a compound, they are called “metal-non-metal binary compounds.” Metals with ions of only 1+, 2+, or 3+ charges in groups IA, IIA, and IIIA are called monoatomic, diatomic and polyatomic ions respectively. Lithium, potassium, and cesium all have a 1+ charge. Beryllium and strontium, in group IIA, are named with the same rules. However, when you name elements in groups IVA–VIIA, where anions of −1, −2, or −3 anions are formed, then “ide” is added to the name.

For example, in naming KCl, the metal is written first, potassium, followed by the non-metal, chloride; potassium chloride. To write the name of Co 2 S 2 , you first name the metal, which is cobalt, followed by the non-metal, sulfur, to get cobalt sulfide. See Chapter 9 for more naming examples.

Polyatomic Ions

You may wonder how to name a compound made up of two non-metals. The same rule applies. Write the non-metal that acts more like a metal, then the other non-metal. Usually, the quasi-metal (non-metal) is close to the zigzag border between metals and non-metals. Carbon is written first in carbon dioxide (CO 2 ). Hydrogen is always written first in compounds such as hydrogen fluoride (HF). Sulfur, nitrogen, and bromine are ordered in naming as in S 4 N 4 or NBr 3 . When several atoms are in a compound, Greek prefixes are used as given in Table 9.2. Examples of this are dinitrogen trioxide (N 2 O 3 ) and carbon tetrafluoride (CF 4 ).

Practice problems for these concepts can be found at – Chemisry and Metals Practice Test

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