Naming Chemical Compounds

What is a compound? A compound is any combination of atoms that are bonded together There are two basic types Ionic compounds and true molecules The type of compound is determined by the type of bonds that hold them together The major types of bonds are ionic and covalent

Ionic bonds In basic terms, ionic bonds are when an atom that is short one or more electrons is electromagnetically attracted to another atom that has too many electrons ionic bonds form between a metal and a non-metal For example, sodium and chlorine

The Octet Rule Think of it this way, atoms want to be stable or satisfied To be satisfied they need a certain number of electrons In the first shell The number is 2 All elements have 2 electrons in the first shell EXCEPT hydrogen, it only has one This means that hydrogen will make chemical bonds in an attempt to get one more electron

The next element on the chart is helium, it has 2 electrons in its shell so it is satisfied and stable so it does few to NO reactions All the elements after helium want 8 electrons in there outer-most shell If they don’t, they will form bonds in an attempt to get eight, hence the “octet rule”

The easiest, least energy consuming method to achieve stability will be employed This means its easier for sodium to give 1 electron to chlorine than it is for chlorine to give sodium 7 electrons This donating of electrons is an ionic bond Thus making NaCl an ionic compound This means it breaks apart into Na ions and Cl ions when put into water

Covalent Bonds These are bonds that form between two non-metals Covalent bonds tend to be stronger than ionic These bonds form when the two atoms share electrons the octet rule still holds true here except that the electrons are shared not “borrowed”

example Carbon can be used to illustrate this Carbon is a non-metal It has a total of 6 electrons Two are found in the first shell that leaves 4 remaining electrons in the outer shell How many does it want to have? Correct, 8

This arrangement means that carbon can make up to 4 different bonds or share electrons with 4 different atoms as long as the arrangement totals 8

Something else to consider The type of bond is a result of the forces of attraction between the protons and electrons in the atom itself and the atom it is bonding to. Also, the size of the atom effects the forces of attraction The bigger the atom the further away the electrons are from the nucleus therefore the smaller the forces of attraction

Naming Compounds Compounds are named according to the elements they contain The system can get complicated But, we can sum it up with 3 guidelines

Guideline 1 The name of the element farther to the left on the periodic table is put first followed by the element farther to the right with the suffix “ide” added to the end NaCl is a compound containing sodium and chlorine Sodium is farther left so it comes first then chlorine but you substitute the “ine” with “ide” NaCl is sodium chloride

Here are a few more HCl is______________ MgO_______________ Sr 3 P 2 _______________

Guideline 2 When two or more non-metal compounds have different numbers of the same elements, prefixes are added to remove the ambiguity Here are the prefixes: –one = mono five = penta –two = di six = hexa –three = tri seven = hepta –four = tetra eight = octa –(sometimes the prefix “mono” is omitted)

examples CO =_____________________ CO 2 = ___________________ NO 2 = ____________________ N 2 O 4 = ___________________ SO 3 = _____________________

Guideline 3 Many compounds are referred to by common names and NOT their systematic name. These common names may be more convenient and/or are traditional

Examples H 2 O is water, nobody calls it dihydrogen monoxide NH 3 is ammonia CH 4 is called methane Pteroenone (compound synthesized from the sea butterfly) is a common name the systematic name is 5(s)-methyl-6(R)-hydroxy-7,9-dimethyl- 7,9-diene-4-undecanone