Compounds and Bonding

CompoundsCompounds = contains two or more different elements chemically bonded together

Most elements are in the form of a compound, very rarely as a single element

Mixture = contains two or more elements or compounds that ARE NOT bonded together

Common CompoundsSalt – NaCl (sodium + chlorine = sodium chloride)Sugar – made up of Carbon, Hydrogen, and oxygen

Sucrose, glucose, fructose…

Properties of CompoundsProperties come more from the structure and composition rather than the elements themselves Example: Aspirin – made up of oxygen, hydrogen and carbon. So is

formaldehyde and polyethlyene (plastic wrap). They even have the same chemical formulas. The properties of aspirin as a pain reliever come from the combination the shape and the bonds

Chemical Bonds

There are two types of chemical bonds:1. Covalent Bonds: valence electrons are shared between two or more elementsNONMETALS

2. Ionic Bonds: valence electrons are transferred from one element to anotherMetal and a Nonmetal

Bonds will be shown by lines or dots. Each line or dot represents and electron

Chemical Formulas Identifies the number and element of each type of

atom in a compound. CH4

H2O

CO2

Covalent BondingSHARED ELECTRONSA group of covalently bonded compounds is called a MOLECULETypically non-metals bonding to other gasses or non-metals

Double and Triple Bonds – represent multiple electrons

Ionic BondingWhen an electron is either lost or gained (transferred)ALMOST ALWAYS includes one metal (metals are conductors – they will always LOSE their electron!)

One electron is transferred from a metal to a non-metal

The bond is based on electrical attractivenessPositive attracting a negative

Ionic Bonding Cont’dWhen an element gains or loses an electron, it becomes an

IONFor example: Salt!

Sodium (Na) is a metal. When it bonds with Chlorine (Cl), Na will lose its one valence electron. Na becomes a positively charged ion, because it lost an electron Cl becomes a negatively charged ion, because it gained an

electron

Another example: MgCl2

DOES NOT BECOME A MOLECULE! Ionic bonds are not limited to one element each, because of the charges, they will be attracted to all neighboring ions.

Hints to remember An element will bond with as many other elements as it has valence

electrons 4 valence electrons means it can make 4 other bonds (wants to get to 8 and

be happy!) 3 valence electrons means it can make 5 other bonds

Covalent bonds are SHARED and form MOLECULES Typically non-metals bonding together in long, complex chains and

compounds

IONIC bonds form IONS!!! Based on charges and gaining and losing electrons Metals bonding with non-metals

Energy in BondingFree atoms contain a large amount of energy

This energy is lost when they bond to another element

Energy is released when chemical bonds formSome elements are more reactive (willing to form bonds and compounds) then others.The closer you are to the noble gasses, the more reactive!Na is highly reactive (1 electron away) and so is Cl (1

electron away). But these elements in pure form together create an explosion!