Biochemistry – the study of the compounds and processes occurring in living things

Table 2.1 Naturally Occurring Elements in the Human Body

Distribution of Subatomic Particles:

Protons – Positive Charge (+)Neutrons – Neutral ChargeElectrons – Negative Charge (-)

*Both protons and neutrons are located in the nucleus of the atom*Electrons are located in energylevels or shells around the nucleus

Two Simplified Models of a Helium (He) Atom

This model was first proposed byNiels Bohr.

Figure 2.9 Energy levels of an atom’s electrons

Electron Distribution in Energy Levels:

First Level: 2 maximumSecond Level: 8 maximumThird Level: 18 maximum

Figure 2.10 Electron configurations of the first 18 elements

Electron Configurations of the First 18 Elements

Isotopes: Atoms of the same element with the same numberof protons but different numbersof neutrons

Examples: Carbon 13 (7 neutrons), Carbon 14 (8 neutrons)

Bond formation and chemical reactions involve the electrons that surround each atom.

What types of bonds are weak?

• van der Waals interactions• hydrogen bonds

Van der Waals Interactionsoccur when transiently positive and negative regions of molecules attract each other

Figure 3.1 Hydrogen bonds between water molecules

What types of bonds are strong?

• Covalent bonds

• Ionic bonds

What sort of covalent bonds are seen here?

Figure 2.14 Electron transfer and ionic bonding

Electron Transfer and Ionic Bonding

Figure 2.15 A sodium chloride crystal

A Sodium-Chloride CrystalThis compoundhas 2 or more elements in definite proportions

A molecule is the smallest part of a compound.

• Water is an example of a polar molecule.

Figure 2.13 Polar covalent bonds in a water molecule

Polar Covalent Bonds in a Water Molecule

Unnumbered Figure (Page 38) Chemical reaction between hydrogen and oxygen

Chemical Reaction Between Hydrogen and Oxygen

Hydrogen Bonds• Oxygen is one of the most

electronegative elements• In a water molecule

electronegative oxygen “hogs” electrons.

• This “hogging” of electrons results in which type of bond between oxygen and hydrogen within the water molecule?

Polar covalent

• Hydrogen bonds

occur between two polar molecules, or between different polar regions of one large macro-molecule.

• One “relatively” negative region is attracted to a second “relatively” positive region.

Figure 3.1 Hydrogen bonds between water molecules

II. Properties of Water

• What are the five characteristics of water that emerge due to this hydrogen bonding?

A. Water is Cohesive and Adhesive

• Cohesion

• Adhesion

• Why is it that a person who jumps off a bridge into water, dies?

Figure 3.2 Water transport in plantsWater Transport in Plants

Figure 3.3 Walking on water

Water has a great surface tension!

B. Moderation of Temperature

• Why is it beneficial if water has a high specific heat?

• Where do we see this characteristic in our lives?

• Pacific Ocean

• Boiling water

C. Water has a High Heat of Vaporization

What does this property of water do?

• Moderates the Earth’s climate

• Stabilizes the temperature of aquatic ecosystems, which effects the life that lives there.

• Allows for evaporative cooling

Figure 3.0 Earth

EvaporativeCooling

D. Water Expands When It Freezes

Important factors that result from water’s expansion as it freezes:

• Prevents deep bodies of water from freezing from the bottom up.

• As water freezes it releases heat to water below and insulates it.

• As water freezes H bonds form releasing heat. As ice melts H bonds break absorbing heat. Both of these factors make seasonal transitions less abrupt!

Why ice really does float:

Figure 3.5 The structure of ice (Layer 2)

The Structure of Ice

E. Water is a Versatile Solvent

• Polar compounds dissolve in water.

• Nonpolar compounds do not dissolve in water.

Figure 3.9 The pH of some aqueous solutions

The pHScale ofSome AqueousSolutions

Review:1) How many protons are in a Nitrogen atom? How many neutrons?2) What do the elements in a family have in common? 3) In Chlorine, the number of electrons in each of the shells is: 4) What is meant by a metalloid?5) What is the atomic mass of Na?6) What is the only subatomic particle that is involved in a chemical reaction?

The type of bond that forms betweenpotassium and fluorine (F) is a/an _________ bond.

How many oxygen atoms are required for photosynthesis to take place?

How many hydrogen and oxygen atoms are in two molecules of carbonic acid, 2H2CO3?

What is the difference between anatom and an element?

Who invented the first periodic table?

A slight attraction or force that results from oppositely charged regions of nearby molecules is called a/an:

Atoms of the same element canhave different numbers of neu-trons. These are called ______of the element.