Naming ionic compounds.
Binary, polyatomic, Transition metal
Positively charged ions are called cations and Negatively charged ions are called anions. An ionic compound is a compound held together by ionic bonds. A binary (bi meaning two) compound simple compound with two elements in it.
Binary compounds are easy to name. The cation is always named first and gets its name from the name of the element. For example, K+ is called a potassium ion. An anion also takes its name from its element, but it adds the suffix -ide to it. So Cl- is called a chloride ion; O2- is an oxide ion.
Take the binary compound NaCl. The Na+ is a sodium cation. The Cl- is a chlorine anion, which gets the suffix -ide added to it. When you put them together, it becomes sodium chloride.
Here are some examples for you.
NaBr - sodium bromide
KBr - potassium bromide
NaCl - sodium chloride
NaF - sodium fluoride
KI - potassium iodide
KCl - potassium chloride
CaCl2 - calcium chloride
K2O - potassium oxide
MgO - magnesium oxide
Most of the Polyatomic ionic compound that contains oxygen. If the polyatomic anion contains oxygen, it is called an oxyanion. If it can form more than one form of oxyanion, it gets a suffix of either -ate or -ite. There are some common oxyanions that most people memorize.
For example:If an oxyanion can form only two different kinds of oxyanions, the name of the ion with the greater number of atoms ends in -ate and the smaller number of atoms ends in -ite.
NO2- is nitrite, with the ending -ite
NO2- is nitrate, with the ending -ate
SO₃2− is sulfite, with the ending -ite
SO₄2−. is sulfate, with the ending -ate
If the ion forms four different kinds of oxyanions, then they get a prefix along with their suffix. The first and lowest size ion gets hypo- as its prefix. The largest size ion gets per- as its prefix. EX-
Transition metal is a metal that can use the inner shell before using the outer shell to bond. These are the elements in the middle of the periodic table, things like zinc and iron and copper. Naming polyatomic ionic compounds that have transition metals in them is also fairly easy. It follows the same naming rules as the simple binary compounds but with an extra rule added in, so you still name the cation first, followed by the anion with the suffix -ide added to the end of it.
The new rule is that transition metals form more than one ion, so this has to be accounted for in the naming. We do this by using Roman numerals to denote which ion it is. The Roman numeral will equal the charge on the ion. For instance, Fe2+ is iron (II). Fe3+ is iron (III).
When compounds are formed with these metals, the different ions still have to be accounted for. If I told you the compound was iron chloride, that wouldn't give you the full story. You wouldn't know if it was iron (II) or iron (III), which means you don't know how many chlorine atoms are in the compound to bond with the iron, since two chlorines would be needed for iron (II) and three for iron (III). If I instead told you that the compound was iron (II) chloride, you would know that it was Fe 2+ in there, which means you have two chlorine atoms bonding with it. The formula would be FeCl2. If I said it was iron (III) chloride, the formula would be FeCl3.
If I told you I had Ag2S, you would know I had silver (I) sulfide. If I gave you FeF2, you would know it was iron (II) fluoride.
What relationship do we see between elements in the same group/family of the Periodic table.
Periods in the periodic table
In each period (horizontal row), the atomic numbers increase from left to right. The periods are numbered 1 through 7 on the left-hand side of the table.
Elements that are in the same period have chemical properties that are not all that similar. Consider the first two members of period 3: sodium (Na) and magnesium (Mg). In reactions, they both tend to lose electrons (after all, they are metals), but sodium loses one electron, while magnesium loses two. Chlorine (Cl), down near the end of the period, tends to gain an electron (it’s a nonmetal).
Families in the periodic table
Members of the families (vertical columns) in the periodic table have similar properties. The families are labeled at the top of the columns in one of two ways:
The older method uses Roman numerals and letters. Many chemists prefer and still use this method.
The newer method uses the numbers 1 through 18.
So why do the elements in the same family have similar properties? You can examine four families on the periodic table and look at the electron configurations for a few elements in each family.
The figure below lists some important families that are given special names:
The IA family is made up of the alkali metals. In reactions, these elements all tend to lose a single electron. This family contains some important elements, such as sodium (Na) and potassium (K). Both of these elements play an important role in the chemistry of the body and are commonly found in salts.
The IIA family is made up of the alkaline earth metals. All these elements tend to lose two electrons. Calcium (Ca) is an important member of the IIA family (you need calcium for healthy teeth and bones).
The VIIA family is made up of the halogens. They all tend to gain a single electron in reactions. Important members in the family include chlorine (Cl), used in making table salt and bleach, and iodine (I).
The VIIIA family is made up of the noble gases. These elements are very unreactive. For a long time, the noble gases were called the inert gases, because people thought that these elements wouldn’t react at all.
A scientist named Neil Bartlett showed that at least some of the inert gases could be reacted, but they required very special conditions. After Bartlett’s discovery, the gases were then referred to as noble gases.