Biology = Chemistry

What do you know?

• What is matter?• What is an element?• What is pH?• What is a subatomic particle? Name them.• Sodium is an explosive metal, chlorine is a toxic gas.

What do you get when they are combined?• What is the building block of life? Why?• What is a polymer?

Atoms and Elements

• What is an atom?• -the smallest unit of an

element defined by its number of subatomic particles

• Subatomic Particles

Proton Neutron Electron

Symbol p+ n e-

Charge +1 0 -1

Elements

• Made entirely of 1 type of atom• Defined by number of protons in the atoms

# protons = Atomic Number of the element, determines place on the periodic table

• Number of protons = number of electrons (why would this be?)

Isotopes

• Electrons determine chemical properities

• Two atoms of the same element with different numbers of neutrons are isotopes

Example: Carbon 12, 13 and 14

Compounds

• Two or more elements together = compound• Can have greatly different properties from the

elements that make them

Example: Dihydrogen monoxide

O2= reactive gas

H2= explosive gas

2H2 + O2 2H2O

• Example 2 Sodium chloride (table salt)

Na (sodium) = explosive metal

Cl2 (chlorine gas) = toxic (mustard) gas

2Na (element) + Cl2 (element) = NaCl (compound)

Chemical Bonding

• General Rule (usually true, not always) : Atoms want 8 valence electrons look like a noble gas

• Ionic Bonds

- 1 or more electrons are transferred from one atom to another

- Creates charged atoms or ions

- Ions are strongly attracted to each other like a balloon and static

- Example : Formation of NaCl

• Covalent Bonding

- Instead of swapping, atoms share electrons to form compounds

- Still form octets but through shared electrons

- Example : formation of water

Strength of Bonds (StrongestWeakest)

• 1. Covalent• 2. Ionic• 3. Hydrogen• 4. Van der Waals forces