By the end of this section, you will be able to: Explain the formation of cations, anions, and ionic compounds Predict the charge of common metallic and nonmetallic elements, and write their electron configurations As you have learned, ions are atoms or molecules bearing an electrical charge. A cation a positive ion forms when a neutral atom loses one or more electrons from its valence shell, and an anion a negative ion forms when a neutral atom gains one or more electrons in its valence shell. Compounds composed of ions are called ionic compounds or saltsand their constituent ions are held together by ionic bonds:
Ionic compounds always contain a metal and a non-metal. Predicting composition A compound is always neutral, and so charges of the ions in the compound must balance out.
We always  know the charges on the ions from the periodic table. So the next stage is to determine the correct ratio of ions that will produce charge neutrality. Basically the total number of positive charges must equal the total number of negative charges. Elements with variable ionic charge We have shown that the periodic table can be used to predict ionic charges.
However, there are some elements that are not susceptible to this approach. Some of the heavier A-type elements like tin and lead show two ionic charge possibilities: The transition metals also show a high degree of variable ionic charges: You are not expected to remember all of these different ions, but be able to predict a composition if given the ion, and write the composition with the correct notation.
Covalent bonding The ionic bonding model works very well for metals and non-metals, but for compounds made exclusively from non-metals, which dominate chemistry in terms of numbers, it fails completely.
This is because non-metals form negative ions and never positive ions. It would also be impossible to describe the bond between the atoms in the diatomic elements like F2, O2 and N2 using the ionic model. In these elements and compounds, covalent bonding operates.
A covalent H—H bond is the net result of attractive and repulsive electrostatic forces. The nucleus—electron attractions blue arrows are greater than the nucleus—nucleus and electron—electron repulsions red arrowsresulting in a net attractive force that holds the atoms together to form an H2 molecule.
The sharing of electrons effectively increases the electron count around the atom. Alone, each fluorine atom has seven electrons in the outer shell. Sharing two electrons in a single covalent bond means that each atom now appears to have eight — it has satisfied its octet demand.
The same principle applies to describing bonds between unlike atoms, such as hydrogen and oxygen in water. Multiple bonds For some molecules, the sharing of two electrons is not sufficient to satisfy the octets of the atoms.
Consider the series F2, O2 and N2. The elements are in groups 7A, 6A and 5A respectively. The atoms have 7, 6 and 5 electrons in the valence shell respectively. It seems pretty obvious that, if the sharing of two electrons in F2 satisfied the octet, then the sharing of two electrons will not do so in O2 or N2.
However, more electrons can be shared, leading to multiple covalent bonds. There is a class of compounds, many of them very familiar, which contain more than two elements and also both ionic and covalent bonding.
The compound is an ionic compound which contains either or perhaps both ions in the form of a polyatomic ion held together by covalent bonds. Most polyatomic ions are negatively charged; only the hydronium ion and the ammonium ion are positively charged.
The rules for balancing the charges in compounds containing polyatomic ions are the same as for binary ionic compounds.
The composition of the polyatomic ion does not change at all.Draw a dot and cross diagram to show how the ionic compound barium chloride is formed from barium and chlorine atoms. Lewis Dot Structures Worksheet - Miss DiSpigna's Chemistry.
Most of the rocks and minerals that surround us are made of ions held together through ionic bonding, the electrical attraction between oppositely charged ions. May 10, · Hence, the writing of Lewis structures corresponding to a given molecular formula is an important exercise for them.
The ability of students to write these structures correctly and then to calculate the formal charges of the atoms involved, is a prerequisite to understanding such topics as: Ionic bonding occurs between metals and.
List the six basic steps used in writing Lewis dot Structures. 5. Explain how to determine Lewis structures for molecules containing single _____ Compared with the neutral atoms involved in the formation of an ionic compound, the crystal lattice that results is weaker than the attractive forces among formula units in ionic bonding.
(c. a Predicting Ionic Formulas. Formula Writing. b Sizes of Ions. Ionic radius vs. Atomic radius. Formation of Binary Ionic Compounds. (Enthalpy) Bond Energ y and Enthalpy DH. The Localized Electron Bonding Model.
Lewis Structures. 70 Lewis Dot Structures Videos. Exceptions to the Octet Rule. Exceptions to the Octet. Bond Formation An ion will form bonds based on how many valence e - ’s (dots) it has: l Less than 4 dots, each dot is an available bonding site.
l 4 or more dots, each missing dot is an available bonding .