You can check your periodic table to see that the cations are monatomic ions formed from metals, and the anions are monatomic ions formed from nonmetals. How do you determine if a pair of elements will most likely form an ionic compound? Chemistry Ionic Bonds Ionic Compounds. Apr 11, Explanation: The chart below shows monatomic ions formed when an atom loses or gains one or more electrons, and the ionic compounds they form.
Individual atoms can gain or lose electrons. When they do, they become monatomic ions. When atoms gain or lose electrons, they usually gain or lose a characteristic number of electrons and so take on a characteristic overall charge. Table 3. There are several things to notice about the ions in Table 3.
First, each element that forms cations is a metal, except for one hydrogen , while each element that forms anions is a nonmetal. This is actually one of the chemical properties of metals and nonmetals: metals tend to form cations, while nonmetals tend to form anions. Second, most atoms form ions of a single characteristic charge.
Thus, if you commit the information in Table 3. In Chapter 9 "Chemical Bonds" , we will discuss why atoms form the charges they do. Third, there are some exceptions to the previous point. A few elements, all metals, can form more than one possible charge. Unfortunately, there is little understanding which two charges a metal atom may take, so it is best to just memorize the possible charges a particular element can have. Note the convention for indicating an ion.
The magnitude of the charge is listed as a right superscript next to the symbol of the element. An element symbol without a charge written next to it is assumed to be the uncharged atom. Naming an ion is straightforward. If the element has more than one possible charge, the value of the charge comes after the element name and before the word ion.
In print, we use roman numerals in parentheses to represent the charge on the ion, so these two iron ions would be represented as the iron II cation and the iron III cation, respectively. For a monatomic anion, use the stem of the element name and append the suffix -ide to it, and then add ion.
This is similar to how we named molecular compounds. Chemical formulas for ionic compounds are called ionic formulas The chemical formula for an ionic compound.
A proper ionic formula has a cation and an anion in it; an ionic compound is never formed between two cations only or two anions only.
The key to writing proper ionic formulas is simple: the total positive charge must balance the total negative charge. Because the charges on the ions are characteristic, sometimes we have to have more than one of a cation or an anion to balance the overall positive and negative charges.
It is conventional to use the lowest ratio of ions that are needed to balance the charges. Each ion has a single charge, one positive and one negative, so we need only one ion of each to balance the overall charge. When writing the ionic formula, we follow two additional conventions: 1 write the formula for the cation first and the formula for the anion next, but 2 do not write the charges on the ions. The formula Na 2 Cl 2 also has balanced charges, but the convention is to use the lowest ratio of ions, which would be one of each.
By convention, the formula is MgO. To balance the charges with the lowest number of ions possible, we need to have two chloride ions to balance the charge on the one magnesium ion. Rather than write the formula MgClCl, we combine the two chloride ions and write it with a 2 subscript: MgCl 2.
What is the formula MgCl 2 telling us? Thus, the charge of a cation formed by the loss of all valence electrons is equal to the group number minus Exceptions to the expected behavior involve elements toward the bottom of the groups.
Transition and inner transition metal elements behave differently than main group elements. Although the d orbitals of the transition elements are—according to the Aufbau principle—the last to fill when building up electron configurations, the outermost s electrons are the first to be lost when these atoms ionize. Write the electron configurations of these cations. Solution First, write the electron configuration for the neutral atoms:. Next, remove electrons from the highest energy orbital.
For the transition metals, electrons are removed from the s orbital first and then from the d orbital. For the p -block elements, electrons are removed from the p orbitals and then from the s orbital. Chromium is a transition element and should lose its s electrons and then its d electrons when forming a cation.
Thus, we find the following electron configurations of the ions:. Check Your Learning Potassium and magnesium are required in our diet. Write the electron configurations of the ions expected from these elements. Most monatomic anions form when a neutral nonmetal atom gains enough electrons to completely fill its outer s and p orbitals, thereby reaching the electron configuration of the next noble gas. Thus, it is simple to determine the charge on such a negative ion: The charge is equal to the number of electrons that must be gained to fill the s and p orbitals of the parent atom.
Oxygen, for example, has the electron configuration 1 s 2 2 s 2 2 p 4 , whereas the oxygen anion has the electron configuration of the noble gas neon Ne , 1 s 2 2 s 2 2 p 6.
The two additional electrons required to fill the valence orbitals give the oxide ion the charge of 2— O 2—. Determining the Electronic Structure of Anions Selenium and iodine are two essential trace elements that form anions.
Determine the moles of calcium chl Watch concept videos about Naming Ionic Compounds. Question What is the formula of the ionic compound expected to form between the elements Al and Cl? Submit Comment. Sign up to view answer. Sign up for free to see the solution Continue with Gmail Continue with Facebook or continue watching with email "Clutch really helped me by reinforcing the things I learned in class and making exam reviews a breeze.
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