1. Chapter 2 Chemical Context of Life
Wakefield
2014

2. EVERYTHING IS MADE UP OF MATTER
ANYTHING THAT TAKES UP SPACE & HAS MASS
MADE UP OF PURE SUBSTANCES CALLED ELEMENTS
ELEMENTS COMBINE TO FORM COMPOUNDS; MANY HAVING EMERGENT PROPERTIES
Example: NaCl
EVERYTHING IS MADE UP OF MATTER

3. M A T T E R

4. M A T T E R ABOUT 92 NATURALLY OCCURRING ELEMENTS
25 OF THESE ARE CONSIDERED ESSENTIAL TO LIFE
4 OF THESE MAKE UP 96% OF LIVING MATTER
CARBON – C
HYDROGEN – H
OXYGEN – O
NITROGEN – N
REMAINING 4% OF LIVING MATTER IS COMPOSED OF P, S, Ca, & K
TRACE ELEMENTS – REQUIRED IN MINUTE AMTS
Fe, I, Mg etc.

5. Sub-Atomic Particles Neu = Neutral Pro = Positive Elec = Negative
Nucleus = Center

6. Atomic Number & Mass
Atomic # = # of Protons in the nucleus of the atom – never changes for each individual element
Atomic Mass = Total of protons and the average # of neutrons of all Isotopes in the nucleus of an atom
Isotope = Varying forms of an element due to varying #’s of neutrons

7. Isotopes

8. Isotopes All atoms of an element have the same # of protons
Some atoms of an element have varying #’s of neutrons – isotopes of that element
The more neutrons an isotope has the less stable it is
Radioactive isotopes occurs when the nucleus of the atom decays spontaneously, giving off particles and energy – This decay leads to a change in the # of protons which eventually transforms it into another element due to the change in protons.

9. Radioactive Isotopes Many Useful Applicaitons: Date fossils Tracers
Metabolism
Production of DNA
Cancer detection
Kidney disorders
Imaging
PET Scans
Hazardous – Radiation Poisoning
Using Radioactivity

10. Energy Levels of Electrons
Energy is the potential to do work
Potential Energy – energy that matter and electrons possess because of its location or structure
The different amounts of potential energy of an atom depends on the structure of the atom / the # and locations of its electrons
Electrons are located in electron shells (electron levels or orbits)
Each shell has a specific # of electron capacity
See Page 36 of Text

11. Energy Levels of Electrons

12. Electron Configuration

13. Electron Configuration
Chemical behavior depends mostly on the # of electrons in the atom’s outermost shell
Valance Electrons - located in the outermost shell or valence shell
If the atom’s valence shell is full it is unreactive otherwise it will readily react with other atoms
Examples are the inert gases – He, Ne, Ar, etc.

14. Chemical Bonding
Chemical Bond – achieved when atoms with incomplete valence shells interact with other such atoms
Covalent Bond – occurs when the atoms share electrons in their valence shells – creates a molecule
Ionic Bond – occurs when the atoms transfer valence electrons – form ionic compounds or salts

15. Chemical Bonding
Molecule – formed when 2 or more atoms bond together by a covalent bond and has its own specific molecular formula (H2O)
Compound – formed when the 2 atoms of a molecule are of different elements
Single bond – 1 pair of shared valence electrons
Double bond – 2 pairs of shared valence electrons
Valence – bonding capacity of an atom

16. Chemical Bonding
Electronegativity – attraction of a particular kind of atom for the electrons of a covalent bond

17. Covalent Bonding
Nonpolar Covalent Bond – all electrons are shared equally

18. Covalent Bonding Nonpolar Covalent Bond
Van der Waal Interaction - Example of weak nonpolar covalent bond
So weak they only occur when atoms and molecules are VERY close together
Biomimicary

19. Covalent Bonding
Polar Covalent Bond – occurs when one atom is bonded a more electronegative atom; hence the electrons, though shared, are not shared equally

20. Ionic Bonding
Occurs when electrons within the molecule are NOT shared but transferred –
may create an ion – (+) or (-) charged particle
Ions are critical in the energy transfer of cellular respiration
Product - ionic compounds or salts
Often found in nature as crystals
The ratio of the molecular formula never changes but the shape of the crystal may

21. Ionic Bonding
Occurs when electrons within the molecule are NOT shared but transferred –
may create an ion – (+) or (-) charged particle
Ions are critical in the energy transfer of cellular respiration
Product - ionic compounds or salts
Often found in nature as crystals
The ratio of the molecular formula never changes but the shape of the crystal may

22. Molecular Shape & Function
Each molecule has a unique shape and size
Its precise shape is critical to its function
Shape determines how biological molecules recognize and respond to one another

23. Chemical Reactions Always has a specific formula
Make and break chemical bonds
Energy is always involved – either used or released
Reactants – starting materials
Products – resulting materials
Activation Energy – energy needed to initiate reaction

24. Chemical Reactions
Chemical Equilibrium – occurs when reactions offset one another completely