CHAPTER 6 – CHEMICAL NAMES AND
FORMULA
Name : Prachayanee
Chueamsuwanna (Tangmo)
CHEMICAL FORMULA
- a chemical is a way of expressing information about the proportions of atoms that
constitute a particular chemical compound.
- there are different types of chemical formulas.
- empirical formula give the lowest whole number ratio of atoms of each element in a
compound.
- molecular formulas give the exact number of atoms of each element in a compound.
- structural formulas show the order in which atoms are bonded.
- condensed formula shows atoms arranged separately but the formula is text based.
- structural formula shows some of the bonds represented by lines in a compound and
some atoms are shown with subscripts.
- displayed (structural) formula shows all atoms and all bonds represented by lines in
a compound.
- skeleton formula apply usually to organic compounds where most hydrogen atoms
are omitted and vertices or line ends represent carbon atoms.
- perspective drawing displayed formula which shows the three dimensional array of
atoms in a compound.
- ball and stick model form of visualizing and representing molecules.
- space filling model is another form of visualizing and representing molecules.
NAMING IONS
- ions are charged atoms or groups of atoms.
- cation is a molecule or atom that has lost one or more electrons forming a positively
charged.
- anoin is a molecule or atom that has gained one or more electrons forming a
negatively charged.
- monoatomic ions are formed from charged single atoms.
- polyatomic ions are charged species or group of charged atoms; they are
comprised of more than one atom bonded to each other.
TABLE
NAMING AND WRITING FORMULAR FOR IONIC
COMPOUNDS
Ionic formulas and Ionic compounds
Because compounds are electrically neutral, one can determine the formula of a
compound this way:
- the charge on the cation becomes the subscripts on the anion
- the charge on the anion becomes the subscript on the cation
- if these subscripts are not in the lowest whole number ratio, divide them by the
greatest common factor.
NAMING AND WRITING FORMULAR FOR IONIC
COMPOUNDS
- binary ionic compounds the cation is named first and then the anion.
- ternary compounds are comprised of three elements. The suffixes –ate and –ite are
used for more complex anions. When cations occur with two different charges the
suffix –ous and –ic were used to designate the lower and higher oxidation states
respectively.
- hydrates are compound that bind water in when crystallized. They are named with
the number of water molecules indicated afterwards.
NAMING AND WRITING FORMULAS FOR
MOLECULAR COMPOUNDS
- a molecule is comprised of atoms held together by chemical bonds.
- several elements occur naturally as diatomic molecules such as hydrogen, oxygen,
nitrogen, fluorine, chlorine, bromine, iodine.
- molecular compounds are composed of different atoms bonded together by
covalent bonds and almost always contain only nonmetals.
- polyatomic molecules are molecules where more than two atoms bonded.
- molecule bear no charge.
- are usually comprised of non metals.
BINARY COMPOUNDS
- the compounds are named based on the order of the elements listed in he formula.
- the first element keeps its name. the first element gets a prefix if it has a subscript
in the formula.
- the ending on the more electronegative element is changed to –ide.
- if the prefix ends with a or o and the name of the element begin with a vowel, the
two successive vowels are often elided into one.
NAMING AND WRITING FORMULAS FOR ACIDS
AND BASES
To name an acids, follow the below general rules:
1. when the name of the anion ends in –ide, the acid names begins with the prefix
hydro. The stem of the anion has the suffix –ic followed by the word acid.
2. when the anion name ends with in –ite the acid name is the stem of the anion with
the suffix –ous followed by the word acid.
3. when the anion name ends with an –ate, the acids name is the stem of the anion
with the suffix –ic, followed by the word acid.
ACIDS
An acid produces a hydrogen cation(proton) when dissolved in water.
- anions whose names end in –ide form acids that are prefixed with “hydro” and the
anion’s suffix becomes “ic”
- gaseous HCI is “hydrogen chloride”
- different number of oxygen atoms may surround the central atom, complicating
nomenclature. The main acids usually has the “ic” suffix. If all protons from the “-ous”
acid is removed the suffix is –ite.
- if only some of the hydrogen atoms are removed, the number of hydrogens left must
be indicated.
BASES
A base is yields an OH- when dissolves in water.
- ammonia, when dissolved in water, also produces hydroxide ions abd is classified as
a base.
- to write the formula for a base, first write the symbol for the metal cation followed
by the formula for the hydroxide ion. Balance the ionic charges like in ionic
compounds.
NAMING AND WRITING FORMULAS FOR SIMPLE
ORGANIC COMPOUNDS
- the rules in the naming of compound help us to know what the compound is from its
name.
- organic compounds are the compounds that are comprised of carbon and hydrogen
primarily, plus whatever other elements are entailed.
- inorganic compounds are all the non-organic compounds.
- organic chemistry is the study of carbon.
- organic chemistry has its own system of nomenclature.
- functional groups determine the chemistry of organic compounds.
NAMING AND WRITING FORMULAS FOR SIMPLE
ORGANIC COMPOUNDS
Introduction to organic compounds
- organic compounds are the compounds that are comprised of carbon and hydrogen
primarily, plus whatever other elements are entailed.
- inorganic compounds are all the non organic compounds.
- organic chemistry is the study of carbon.
- organic chemistry has its own system of nomenclature.
- straight chain hydrocarbons are named with the Greek numerical prefix for the
number of carbon atoms, and the suffix “-ane.”
- the first four, do not use the Greek prefix: Methane, Ethane, propane, and butane.
-functional groups determine the chemistry of organic compounds.
NAMING AND WRITING FORMULAS FOR SIMPLE
ORGANIC COMPOUNDS
The three common hydrocarbons are shown:
- single bond (alkane) : suffix is “ane”, are formula
proprane, and butane
- double bond (alkene) : suffix is “ene”, formula
etc.
- triple bond (alkyne) : suffix is “yne”, formula
etc.
eg. Methane, ethane,
eg. Ethane, propene, butane
eg. Ethyne, propyne, butyne
- when a hydrogen in an alkane is replaced with something else the name is derived
from the name of the alkane.
- the ending denotes the type of compound.