Putting Elements Together

1
Putting Elements Together
Chemical Bonding
Chemical bonding allows atoms and molecules to
stick together.

• If a sample of matter contains two or more
  elements chemically combined in a certain ratio,
  it is called a compound.
• Examples water (H2O), salt (NaCl), and glucose
  (sugar) C6H12O6
• Compounds have properties that are different from
  the elements it contains.

2
Types of Chemical Bonding
STRONG

• Covalent Bonding Atoms share electrons.
• Ionic Bonding Atoms gain or lose electrons to
  form charge particles called ions. Ions then
  bond together because opposite charges attract.
• Hydrogen Bonding Molecules stick together
  because certain parts of them are charged. The
  oppositely charged parts stick together.

WEAK
3
Covalent Bonding
Covalent Bonds form when atoms SHARE a pair of
electrons. This fills their outer valence shell.
Two or atoms held together by covalent bonds is a
molecule. Ex. H2O, O2, HCl, O3
They may share more than one bond between two
atoms
4
Water molecules attract by weak hydrogen bonds
Inside the Molecule covalent bonds
Cohesion like molecules stick together Adhesion
unlike molecules stick together
Water Water Water
5
Importance of Water

• Water molecules are polar
• Electronegativity
• Hydrophobic vs. hydrophilic
• Water molecules are cohesive
• Hydrogen bonds
• Water has a high specific heat
• Water can resist temp. change
• Important to cells regulates
• ecosystem climate
• Water is the universal solvent
• Dissolves/carries nutrients
• Cellular Transport

6
Strong cohesive forces between water molecules
create surface tension in water - droplets
Capillary action is created by the adhesion of
water to vessel walls and creates surface tension
(meniscus curve)
Special Properties of Water
7

• Knowing about the structure of atoms can help us
  understand the functions of certain elements in
  living things.

8
IONIC BONDING
how does salt form?
Na (1 valence e-) Cl (7 valence e-)
Na Cl-

• Ionic bonds form between metals and non-metals,
• Ionic compounds dissolve easily in water and
  other polar solvents
• In solution, ionic compounds easily conduct
  electricity,

9
Covalent vs. Ionic Bonding