The Chemical Compounds of Life

Basic chemistry

Matter

• Anything that has mass and takes up space is matter.

• There are about 103 naturally occurring different types “building materials” of matter; we call these types elements.

Atoms

• The smallest particle of an element that has all the properties of that element and that can’t be broken down by ordinary physical or chemical means.

Atom structure

http://www.classzone.com/books/earth_science/terc/content/investigations/es0501/es0501page03.cfm?chapter_no=investigation

Protons

• Atomic number gives the number of protons in an atom.

• The number of protons in an atom determine its essential character.

• Changing the number of protons changes the element.

Neutrons

• Neutrons are found in the nucleus with protons.

• The atomic mass number gives the number of neutrons PLUS the number of protons.

• Neutron number can vary somewhat.

Electrons

• Electrons carry a tremendous amount of energy.

• # of electrons is usually equal to # of protons.

• Arrangement of electrons determines how an atom will interact with other atoms.

Building an atom

• http://www.classzone.com/books/earth_science/terc/content/investigations/es0501/es0501page05.cfm

• http://www.kscience.co.uk/animations/atom.htm

Practice!

Isotopes

• An isotope is an atom with an unusual number of neutrons.

• Different elements have different numbers of possible isotopes.

• Carbon has 4 isotopes.

Isotopes of carbon

Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14

6 electrons6 protons6 neutrons

6 electrons6 protons8 neutrons

6 electrons6 protons7 neutrons

Valence electrons

• Atoms “want” to have a filled valence and will interact with other atoms to get it.

• May gain or lose electrons – ionic bond

• May share electrons – covalent bond

Ions

• An ion is an atom with an electrical charge.

• Created by gaining or losing electrons.

• Cation – positively charged ion.

• Anion – negatively charged ion.

Ionic bonds

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Sodium atom (Na) Chlorine atom (Cl)

Transferof electron

Ionic bonds

Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na+) Chloride ion (Cl-)

Transferof electron

Protons +11Electrons -11Charge 0

Protons +17Electrons -17Charge 0

Protons +11Electrons -10Charge +1

Protons +17Electrons -18Charge -1

Ionic bonds

• Transfer of an electron leaves the Na atom as a positive ion (Na+) and the Cl atom as a negative ion (Cl-).

• What happens to particles with opposite charges?

• Resulting substance is called a compound, and we can write a chemical formula for it: NaCl

Ionic bonds

• Remember that each atom wants to have a filled valence.

• Consider Magnesium (atomic # 12) and Chlorine (atomic # 17): describe the bond that forms.

Covalent bonds

• Two atoms may come close enough to share electrons.

• Each atom “feels” like it has a full valence.

• Formation of the bond releases energy and the resulting substance acts like a single unit.

• Creates molecules.

A water molecule

Covalent bond

Covalent bond

Hydrogen bonds

• Weak attractions between polar molecules that contain hydrogen atoms.

• Important in forming complex shapes in large molecules.

• More on these later…