N Order for a Negative Ion to Become Stable Again It Must Lose an Electron

Learning Objective

• Predict whether an cantlet will undergo ionization to provide an anion or cation based on its valence crush electron configuration.

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Key Points

• The electronic configuration of many ions is that of the closest element of group 0 to them in the periodic table.
• An anion is an ion that has gained one or more electrons, acquiring a negative charge.
• A cation is an ion that has lost one or more electrons, gaining a positive charge.

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Terms

• cationA positively charged ion, equally opposed to an anion.
• ionizationAny process that leads to the dissociation of a neutral cantlet or molecule into charged particles (ions).
• anionA negatively charged ion, equally opposed to a cation

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Cations and Anions form from Neutral Atoms

Every cantlet in its basis state is uncharged. It has, co-ordinate to its atomic number, the same number of protons and electrons. Electrons are rather labile, however, and an atom will often gain or lose them depending on its electronegativity. The driving force for such gain or loss of electrons is the energetically optimal state of having a full valence (outermost) shell of electrons. In such a land, the resulting charged cantlet has the electron configuration of a noble gas.

Addition of an electron will disrupt the proton-electron residual and get out the cantlet negatively charged. Removal of an electron will, conversely, leave the atom positively charged. These charged atoms are known equally ions.

Formation of Monatomic Ions

Monatomic ions are formed by the improver or removal of electrons from an cantlet's valence shell. The inner shells of an cantlet are filled with electrons that are tightly bound to the positively charged diminutive nucleus and then do not participate in this kind of chemical interaction, just the valence beat can be very reactive depending on the atom and its electron configuration. The process of gaining or losing electrons from a neutral atom or molecule is called ionization.

Atoms can exist ionized by bombardment with radiation, but the more than purely chemical process of ionization is the transfer of electrons between atoms or molecules. This transfer is driven by the stabilization that comes by obtaining stable (total shell) electronic configurations. Atoms volition gain or lose electrons depending on which activeness takes the least energy.

For example, Group 1 chemical element sodium (Na) has a single electron in its valence shell, with total shells of 2 and 8 electrons beneath. Removal of this i electron leaves sodium stable: Its outermost shell now contains viii electrons, giving sodium the electron configuration of neon. Having gained a positive accuse, the sodium ion is called a cation. The ionization of sodium can be chemically illustrated as follows:

Na → Na⁺ + e⁻

Sodium could gain electrons, but it would crave seven more to achieve a full valence trounce. Removing one electron is much easier than gaining seven, and thus sodium volition in every chemical scenario achieve its octet by becoming a cation.

On the other paw, a chlorine atom (Cl) has vii electrons in its valence shell, which is one short of a stable, full shell with eight electrons. Thus, a chlorine atom tends to gain an extra electron and reach a stable 8-electron configuration (the same as that of argon), becoming a negative chloride anion in the process:

Cl + e− → Cl⁻

Combining the propensity of sodium to lose an electron and of chloride to proceeds an electron, we observe complimentary reactivity. When combined, the uncharged atoms can commutation electrons and in doing so, reach complete valence shells. The resulting ions stick together due to ionic bonds (opposite charges attract), leaving a crystal lattice structure of NaCl, more normally known as rock salt. The reaction is equally follows:

Na⁺ + Cl⁻ → NaCl

Polyatomic and Molecular Ions

Ionization is non express to individual atoms; polyatomic ions tin can as well be formed. Polyatomic and molecular ions are often created by the add-on or removal of elemental ions such as H⁺ in neutral molecules. For example, when ammonia, NH_three, accepts a proton, H⁺, it forms the ammonium ion, NH_iv ⁺. Ammonia and ammonium have the same number of electrons in essentially the aforementioned electronic configuration, but ammonium has an actress proton (the H⁺) that gives it a net positive charge.

Chemical Note

When writing the chemical formula for an ion, its cyberspace charge is written in superscript immediately after the chemic construction for the molecule or atom. The net accuse is written with the magnitude before the sign, that is, a doubly charged cation is indicated equally ii+ instead of +2. However, the magnitude of the charge is omitted for singly charged molecules or atoms; for example, the sodium cation is indicated as Na⁺ and not Na^ane+.

An alternative way of showing a molecule or atom with multiple charges is by drawing out the signs multiple times; this is often seen with transition metals. Chemists sometimes circle the sign; this is only ornamental and does not alter the chemical meaning. A twice-positively charged fe cantlet tin also be expressed as Fe²⁺ or Fe⁺⁺.

In the example of transition metals, oxidation states can be specified with Roman numerals; for example, Iron^two+ is occasionally referred to as Atomic number 26(II) or Atomic number 26^II. The Roman numeral designates the formal oxidation state of an element, whereas the superscripted numerals denotes the net charge. The 2 notations are therefore exchangeable for monatomic ions, but the Roman numerals cannot exist practical to polyatomic ions. Even so, it is possible to mix the notations for the individual metal center with a polyatomic circuitous, as demonstrated using the uranyl ion (UO_ii) as an example.

It should be noted that it is possible to remove many electrons from an atom. The free energy required to do so may be recorded in a successive ionization free energy diagram.

First ionization free energyPeriodic trends for ionization energy (IE) vs. diminutive number: notation that within each of the 7 periods the IE (colored circles) of an element begins at a minimum for the start column of the Periodic table (the brine metals), and progresses to a maximum for the terminal column (the noble gases) which are indicated past vertical lines and labelled with a element of group 0 chemical element symbol, and which also serve equally lines dividing the 7 periods. Annotation that the maximum ionization energy for each row diminishes every bit one progresses from row 1 to row 7 in a given column, due to the increasing distance of the outer electron shell from the nucleus every bit inner shells are added.

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Source: https://courses.lumenlearning.com/introchem/chapter/electron-configuration-of-cations-and-anions/

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