CHM 161 Chapter 5: Ionic and covalent chemical bonding

Ionic Bonding

A type of chemical bond where one atom transfers electrons to another, resulting in the attraction between oppositely charged ions.

Cation

A positively charged ion formed when an atom loses one or more electrons.

Anion

A negatively charged ion formed when an atom gains one or more electrons.

Binary Ionic Compounds

Compounds composed of two different elements, one being a cation and the other an anion.

Oxoanions

Polyatomic ions that contain oxygen and another element.

Electronegativity

The ability of an atom to attract electrons in a covalent bond.

Octet Rule

The principle that main-group elements tend to bond in such a way that they each have eight valence electrons.

Lewis Electron-Dot Structures

Diagrams that show the valence electrons of atoms within a molecule.

Bond Dissociation Energy (BDE)

The energy required to break a covalent bond; always a positive value.

Molecular Mass

The sum of the atomic weights of all atoms in a molecule.

Formula Mass

The mass per formula unit of an ionic compound.

Polar Covalent Bonds

Covalent bonds where the electrons are shared unequally between the two atoms, resulting in partial charges.

Bond Dipole Moment

A measure of the separation of positive and negative charges in a polar bond.

Ions

A species with an overall electric charge.

ionic compounds

A compound formed from positive and negative ions.

Remember that ions are formed only when ______ move from one atom to another;

Electrons

monatomic ions

a charged particle made of only one atom

chemical formula

A list of elements in a compound.

ionic formulas

The chemical formula for an ionic compound.

What is the key to writing proper ionic formulas

the total positive charge from the cation(s) must balance the total negative charge from the anion(s).

When writing the ionic formula, we follow two conventions, what are they?

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.

polyatomic ions

An ion that contains more than one atom. Can have an overall charge and make ionic compounds.

What is the name of the molecule PCl₃?

phosphorus trichloride

What is the name of the molecule N₂O?

Nitrous oxide

What is the name of the molecule S₂F₆?

Disulfur hexafluoride

Lewis electron dot diagram

A representation of the valence electrons of an atom that uses dots around the symbol of the element.

octet rule

The trend that atoms like to have eight electrons in their valence shell. This is generally achieved through bonding with other atoms.

Ionic bonds are caused by

electrons transferring from one atom to another.

molecules

The smallest part of a substance that has the and chemical properties of that substance. Composed of more than one atom.

diatomic molecules

A molecule with only two atoms.

molecular formula

A formal listing of what and how many atoms are in a molecule.

Chemical Bond

The connection between two atoms in a molecule.

chemical nomenclature

A very specific system for naming compounds, in which unique substances get unique names.

covalent bond

A chemical bond formed by two atoms sharing electrons.

single bond

A covalent bond composed of one pair of electrons.

bonding electron pair

A pair of electrons that makes a covalent bond.

lone electron pairs

A pair of electrons that does not make a covalent bond.

nonpolar covalent bond

The equal sharing of electrons in a covalent bond.

polar covalent bond

The unequal sharing of electrons in a covalent bond.

electronegativity

A qualitative scale for judging how much atoms of any element attract electrons.

If the Electronegativity Difference is 0 the bond is likely

a nonpolar covalent bond.

If the Electronegativity Difference is 0-0.4 the bond is likely

a slightly polar covalent bond.

If the Electronegativity Difference is 0.4-1.9 the bond is likely

a polar covalent bond.

If the Electronegativity Difference is >1.9 the bond is likely

ionic

bond energy

The approximate amount of energy needed to bread a covalent bond.

Odd-electron molecules

A molecule with an odd number of electrons in the valence shell of an atom.

Electron-deficient molecules

A molecule with less than eight electrons in the valence shell of an atom.

expanded valence shell molecules

A molecule with more than eight electrons in the valence shell of an atom.

What is the proper formula for lithium carbonate?

Li₂CO₃

What is the proper formula for calcium sulfite?

CaSO₃

The ionic compound CaCl₂ has what name?

calcium chloride

What is the name of Na₂SO₃?

Sodium sulfite

What is the name of BaCO₃?

barium carbonate

How are ions formed from neutral atoms? 

Atoms either gain or loose electrons

What is the formula for the ionic compound cobalt(III) carbonate?

Co2(CO₃)₃