What makes ionic compounds neutral
Monatomic Cations: When atoms typically metals lose one or more electrons to become positively charged cations. So, why does sodium lose one electron while magnesium loses two electrons?
The charge of main group elements can be determined by the group number with the "A" designation. Metals in groups 1A-3A lose the same amount of electrons as in their group number. This results in atoms with the same number of electrons as the noble gas directly preceding the element more details on this when we do electron configurations later in this text.
When we name monatomic cations ions that form only on charge like those in Groups 1A-3A, we simply identify the name of the element followed by the word ion.
Although hydrogen has one electron in its outer shell like all the alkali metals , it only has one electron and so completely removing it would leave behind a bare nucleus which would not be stable. 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? The substances described in the preceding discussion are composed of molecules that are electrically neutral; that is, the number of positively-charged protons in the nucleus is equal to the number of negatively-charged electrons. In contrast, ions are atoms or assemblies of atoms that have a net electrical charge.
Ions that contain fewer electrons than protons have a net positive charge and are called cations. Conversely, ions that contain more electrons than protons have a net negative charge and are called anions.
Ionic compounds contain both cations and anions in a ratio that results in no net electrical charge. In covalent compounds, electrons are shared between bonded atoms and are simultaneously attracted to more than one nucleus. In contrast, ionic compounds contain cations and anions rather than discrete neutral molecules. Ionic compounds are held together by the attractive electrostatic interactions between cations and anions.
The electrostatic energy is negative only when the charges have opposite signs; that is, positively charged species are attracted to negatively charged species and vice versa. Ionic compounds contain both cations and anions in a ratio that results in zero electrical charge. These energetic factors are discussed in greater quantitative detail later.
If the electrostatic energy is positive, the particles repel each other; if the electrostatic energy is negative, the particles are attracted to each other. In forming chemical compounds, many elements have a tendency to gain or lose enough electrons to attain the same number of electrons as the noble gas closest to them in the periodic table. They then have the same number of electrons as the nearest noble gas: neon. This particular resource used the following sources:. Skip to main content.
Atoms, Molecules, and Ions. Search for:. Ionic Bonds. Learning Objective Summarize the characteristic features of ionic bonds. Key Points Ionic bonds are formed through the exchange of valence electrons between atoms, typically a metal and a nonmetal. The loss or gain of valence electrons allows ions to obey the octet rule and become more stable. Ionic compounds are typically neutral. Therefore, ions combine in ways that neutralize their charges.
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