How can ionic compounds be neutral

This gives it a single negative charge, and it is now a chloride ion Cl — ; note the slight change in the suffix -ide instead of -ine to create the name of this anion. Fig 3. On the left, a chlorine atom has 17 electrons. On the right, the chloride ion has gained an extra electron for a total of 18 electrons and a 1 — charge. Note that the chloride ion has now filled its outer shell and contains eight electrons, satisfying the octet rule. Group VIA elements gain two electrons upon ionization, obtaining -2 charges and reaching the electron configurations of the noble gases that follow them in the periodic table.

Whereas, Group VA elements gain three electrons, obtaining -3 charges and also reaching the electron configurations of the noble gases that follow in the periodic table. When nonmetal atoms gain electrons, they often do so until their outermost principal energy level achieves an octet.

This process is illustrated below for the elements fluorine, oxygen, and nitrogen. All of these anions are isoelectronic with each other and with neon. They are also isoelectronic with the three cations from the previous section. Under typical conditions, three electrons is the maximum that will be gained in the formation of anions. It is important not to misinterpret the concept of being isoelectronic.

A sodium ion is very different from a neon atom because the nuclei of the two contain different numbers of protons. One is an essential ion that is a part of table salt, while the other is an unreactive gas that is a very small part of the atmosphere. Neon atoms and sodium ions are isoelectronic. Neon is a colorless and unreactive gas that glows a distinctive red-orange color in a gas discharge tube. Sodium ions are most commonly found in crystals of sodium chloride, ordinary table salt.

The transition metals are an interesting and challenging group of elements. Predicting how they will form ions is also not always obvious. Transition metals belong to the d- block, meaning that the d- subshell of electrons is in the process of being filled with up to ten electrons.

Many transition metals cannot lose enough electrons to attain a noble-gas electron configuration. In addition, the majority of transition metals are capable of adopting ions with different charges. According to the Aufbau process, the electrons fill the 4 s sublevel before beginning to fill the 3 d sublevel. However, the outermost s electrons are always the first to be removed in the process of forming transition metal cations.

This is the case for iron above. This is because a half-filled d subshell d 5 is particularly stable, which is the result of an iron atom losing a third electron. It has been known since ancient times as green vitriol and was used for centuries in the manufacture of inks. Some transition metals that have relatively few d electrons may attain a noble gas electron configuration. Scandium is an example. Others may attain stable configurations with a full d-subshell , such as zinc and copper.

The resulting configuration above, with 18 electrons in the outermost principal energy level, is referred to as a pseudo noble-gas electron configuration. For elements that have more than one common ionic state, both states are listed. For the printable PDF version of this table with the common polyatomic ions , click the link below:. Periodic Table with Ions. An ionic compound is an electrically neutral compound consisting of positive and negative ions.

You are very familiar with some ionic compounds such as sodium chloride NaCl. Anions and cations have opposing charges. Because of this, they are attracted to one another.

When an anion and a cation are drawn together due to this electrostatic attraction, they can form an ionic bond. This kind of bond is the result of opposing charges attracting one another, and is distinct from other types of bonding. Two or more ions bound by electrostatic attraction make an ionic compound. The simplest ionic compounds are binary ionic compounds or those that only contain two atoms, one acting as the cation, and one acting as the anion.

Thus, we will focus on the formation of binary ionic compounds first. Sodium chloride, or table salt, is an ionic compound. During the formation of sodium chloride, the electron given off by sodium is taken by chlorine, forming the chloride ion.

The chloride ion has one excess electron, giving it a -1 charge. The result of this electron transfer is that the sodium cation and chloride anion become bound through electrostatic attraction, forming sodium chloride, an ionic compound.

Ionic reactions can be represented by electron dot diagrams, as shown below for sodium chloride. It is conventional to show the cation without dots around the symbol to emphasize that the original energy level that contained the valence electron is now empty. The anion is now shown with a complete octet of electrons. The final formula for sodium chloride is NaCl. Notice that both ions are represented but their charges are not shown. This is because within ionic compounds the overall charge on the compound is zero, i.

Also note that in chemical formulas that the cation always comes first and the anion is always placed second in the formula. For a compound such as magnesium chloride, it is not quite as simple. Because magnesium has two valence electrons, it needs to lose both to achieve the noble-gas configuration.

Therefore, two chlorine atoms will be needed. The final formula for magnesium chloride is MgCl 2. Note that the subscript 2 next to the chloride ion, indicates that there are two chloride ions paired with each magnesium cation. When there is only one ion present in a formula, i. As in the case of NaCl, there are no charges shown in the final formula of MgCl 2. To predict and write correct chemical formulas, the key fundamental steps that are required, are 1 knowing the charge states of the ions and 2 using basic math to help you determine how many cations and anions are needed to reach a zero charge state, 3 writing the chemical forumulas with the cation first followed by the anion, and 4 writing the formula with the lowest ratio of cations and anions to create a net neutral compound.

Overall, ionic bonding occurs between a cation electron donor and an anion electron acceptor to form a compound that has an overall neutral net charge.

Of note, ionic bonds usually occur between a metal and a nonmetal. This will help you recognize ionic compounds more easily, once we learn about covalent bonding which occurs most commonly between two nonmetals, or between a nonmetal and a semimetal metalloid. What is the correct ionic formula? To begin this type of problem, I recommend drawing out a charge box or a charge table to help you keep track of the number of ions used, the charges of those ions, and the overall positive and negative charges on the molecule.

Drawing out the electron dot symbols can also be helpful. Here is an example of a generic charge box. So now we have our charge box set up with our known information. Now we need to figure out how many atoms of the cation and the anion are required to cancel out the overall positive and negative charge on the resulting molecule. To do this, it is often useful to use the cross-multiplication strategy, where you try using the charge number for the cations, as the number of atoms of anion required, and the charge number for the anion as the number of atoms of the cation required.

Multiply each of the ion charges by the number of atoms to calculate the total ion charges of the cation s and anion s present and then add these numbers together to find the total charge on the compound. This will usually get you to the stable ionic formula that has a net neutral charge of zero. The of atoms column then becomes the subscripts that you need to use to construct the correct ionic formula.

In this case 1 atom of iron Fe with 3 atoms of chlorine Cl for a formula of FeCl 3. The previous example is pretty straight forward, and you may have been able to construct the formula in you head. However, as the complexity of formula making increases, it is good to be able to use the charge box method to double check your work.

For example, what would the correct ionic formula be for aluminum sulfide? First, identify the two atoms involved Aluminum and Sulfur and start building your charge box with what you know from the periodic table. From the periodic table in Figure 3. For Step 2: Use the cross multiply rule to predict how many atoms will be needed from each type and multiply through the total ion charge for both the cation and anion.

Ionic solids are typically represented by their empirical formulas. In formula notation, the elements are represented by their chemical symbols followed by numeric subscripts that indicate the relative ratios of the constituent atoms.

The complete formula for an ionic compound can be determined by satisfying two conditions:. For example, in the reaction of calcium and chlorine, the compound is called calcium chloride. Its ionic formula is written as CaCl 2 , the neutral combination of these ions. Polyatomic ions are a set of covalently bonded atoms that have an overall charge, making them an ion. For example, the hydroxide ion has the formula OH Because you will use them repeatedly, they will soon become familiar.

Note that there is a system for naming some polyatomic ions; -ate and -ite are suffixes designating polyatomic ions containing more or fewer oxygen atoms. The nature of the attractive forces that hold atoms or ions together within a compound is the basis for classifying chemical bonding.

When electrons are transferred and ions form, ionic bonds result. Ionic bonds are electrostatic forces of attraction, that is, the attractive forces experienced between objects of opposite electrical charge in this case, cations and anions.

Covalent bonds are the attractive forces between the positively charged nuclei of the bonded atoms and one or more pairs of electrons that are located between the atoms. Compounds are classified as ionic or molecular covalent on the basis of the bonds present in them. When an element composed of atoms that readily lose electrons a metal reacts with an element composed of atoms that readily gain electrons a nonmetal , a transfer of electrons usually occurs, producing ions. The compound formed by this transfer is stabilized by the electrostatic attractions ionic bonds between the ions of opposite charge present in the compound.

A compound that contains ions and is held together by ionic bonds is called an ionic compound. The periodic table can help us recognize many of the compounds that are ionic: When a metal is combined with one or more nonmetals, the compound is usually ionic.

This guideline works well for predicting ionic compound formation for most of the compounds typically encountered in an introductory chemistry course. However, it is not always true for example, aluminum chloride, AlCl 3 , is not ionic. You can often recognize ionic compounds because of their properties. Ionic compounds are solids that typically melt at high temperatures and boil at even higher temperatures. When molten, however, it can conduct electricity because its ions are able to move freely through the liquid Figure 3.

Figure 3. In every ionic compound, the total number of positive charges of the cations equals the total number of negative charges of the anions. Thus, ionic compounds are electrically neutral overall, even though they contain positive and negative ions. We can use this observation to help us write the formula of an ionic compound. The formula of an ionic compound must have a ratio of ions such that the numbers of positive and negative charges are equal.

What is the formula of this compound? Figure 4. Although pure aluminum oxide is colorless, trace amounts of iron and titanium give blue sapphire its characteristic color.

Because the ionic compound must be electrically neutral, it must have the same number of positive and negative charges.

The formula would be Al 2 O 3. Many ionic compounds contain polyatomic ions Table 1 as the cation, the anion, or both.

As with simple ionic compounds, these compounds must also be electrically neutral, so their formulas can be predicted by treating the polyatomic ions as discrete units. Consequently hydrogen does not form a cation, but can result in an acid, which is a polar covalent bond. If chlorine was to try and remove the electron from hydrogen, it would not be able to as the resulting nucleus would pull it back, this results in the acid HCl, where the chlorine can not completely remove the electron from the hydrogen.

Monatomic Anions: when atoms typically non-metals gain one or electrons to become negatively charged anions. For example, when a neutral fluorine atom gains one electrons, it becomes the fluoride ion as shown by the following shorthand notation:. Another example is the formation of the sulfide ion when a neutral sulfur atom gains two electrons picking up a -2 charge. As you may have inferred, the position of the main group non-metal on the periodic table can also be used to predict its charge.

If you subtract eight from the group number of the element in groups 5A-7A, you will be able to predict the charge of the anion. This allows the atoms of a given nonmetal to gain enough electrons so as to have the same number of electrons as the noble gas following the element.

When sulfur gains two electrons, it will have 18 electrons, like argon. We will go into the reasoning behind this in later chapters. Finally, when monatomic anions are named, you must change the -ine end of the element's name to the -ide ending following by the word ion. For example, F - is named as fluoride ion to differentiate it from F, the fluorine atom.

To help you remember these patterns, think about metals everything to the left of the stairs as positively charged, and think about the non-metals everything to the right of the stairs as negatively charged.

You may have noticed that the transition metals have more than one charge. The charge of the transition metals is not as easily determined as the main group elements. Because they can potentially have more than one charge, it is important to differentiate between ions of the same element by adding a Roman Numeral in parenthesis after the element name following by the word ion.

Note, the older system assigned the ion with the lower charge with the -ous ending and the ion with the greater charge with the -ic ending. When more than one type of atom is covalently bonded and has an overall charge, this is known as a polyatomic ion. When forming a stable crystal, these compounds have both covalent bonds holding the polyatomic ion s together and ionic bonds holding the different ions together in a stable neutral lattice. Below is a list of polyatomic ions that you will be required to know.

The formula of an ionic compound represents the lowest whole number ratio of cations to anions, it is as simple as that. What is the case when we write ionic formula that include polyatomic ions?