Adv Biology

Chapter 2Inorganic and Organic

Chemistry

Levels of chemical organization

• Matter• Atoms• Elements, Molecules, and

Compounds

Matter …is anything that occupies space and

has mass.

Molecules are particles of matter that are composed of one or more smaller units called atoms.

Classification of substances• elements- are pure substances• molecules-are united atoms forming

larger chemical units• compounds- are substances whose

molecules have more than one element in them.

The AtomName the parts of

an atom1. ?2. ??3. ???4. ????

Parts of an atomIdentify the

charge of the particles of the atom– Proton– Electron– Neutron

Parts of an atom

The charges of the particles of the atom:– Proton + positive

– Electron - negative

– Neutron 0 no charge

Elements A symbol is one

or two letters used to represent an element

– C for Carbon– Al for aluminum– S for sulfur– Cu for copper

Did you know?• Elements are substances consisting

of one type of atom, for example Carbon atoms make up diamond, and also graphite.

• Pure (24K) gold is composed of only one type of atom, gold atoms.

• Atoms are the smallest particle into which an element can be divided.

and Elements differ from each other in

the number of protons they have, e.g. Hydrogen has 1 proton; Helium has 2.

Arranging the elements• The elements are arranged by their

atomic number which is equal to the number of protons for each element. The number of protons is equal to the number of electrons.

• The atomic mass is equal to the number of protons and neutrons in the nucleus.

• The periodic table is used in the study of chemistry.

The Periodic Table of the Elements

• Each Roman numeraled column on the label (at least the ones ending in A) tells us how many electrons are in the outer shell of the atom.

• Each numbered row on the table tells us how many electron shells an atom has. Thus, Hydrogen, in column IA, row 1 has one electron in one shell.

• Phosphorous in column VA, row 3 has 5 electrons in its outer shell, and has three shells in total.

Human elements…• Four kinds of atoms make up 96% of

the human body. The major elements include– oxygen– carbon– hydrogen– nitrogen

• There are traces of about 20 other elements in the body and known as trace elements

Compounds… are substances

whole molecules have more than one element in them. Examples include– carbon dioxide– sodium chloride– water

Formula… for a compound

contains the symbols for the elements in each molecule

     Saccharin's chemical formula is C7H5O3NS

Aspartame's chemical formula is C13H18O5N2

Electron orbitals

• Negatively charged electrons surround the nucleus at a distance.

• They move about within certain limits called orbitals.

• Orbitals are arranged into energy levels (shells), depending on their distance from the nucleus.

Ionic bonds• Ionic bonds are formed when atoms

become ions by gaining or losing electrons. • Chlorine is in a group of elements

having seven electrons in their outer shells.

• Members of this group tend to gain one electron, acquiring a charge of -1.

• Sodium is in another group with elements having one electron in their outer shells.

Covalent bonds• Covalent bonds form when atoms share

electrons. • Since electrons move very fast they can be

shared, effectively filling or emptying the outer shells of the atoms involved in the bond.

• Such bonds are referred to as electron-sharing bonds.

• An analogy can be made to child custody: the children are like electrons and tend to spend some time with one parent and the rest of their time with the other parent.

Ways of representing covalent bonds.

Hydrogen bonds• Hydrogen bonds result from the weak

electrical attraction between the positive end of one molecule and the negative end of another.

• Individually these bonds are very weak, although taken in a large enough quantity, the result is strong enough to hold molecules together or in a three-dimensional shape.

Examples of hydrogen bonds

Chemical reactions and molecules

Molecule versus Mixture: Molecules are compounds with elements in definite, fixed ratios. Those atoms are held together usually by one of the three bonds discussed above. For example: water, glucose, ATP.

Mixture ~ Molecule Mixtures are compounds with variable

formulas/ratios of their components. For example: soil.

Molecular formulas are an expression in the simplest whole-number terms of the composition of a substance. For example, the sugar glucose has 6 Carbons, 12 hydrogens, and 6 oxygens per repeating structural unit. The formula is written C6H12O6.