1. The Chemical Context of Life
Chapter 2
The Chemical Context of Life

2. Chemistry Definition Matter Transformations
Study of matter and its transformations
Matter
Has mass and occupies space
Transformations
Chemical reactions
Break or form chemical bonds

3. Units of Matter Element Compound Molecule
Substance that cannot be broken down further by chemical means
Compound
Substance composed of more than one element
Molecule
Substance composed of more than one atom
Includes diatomic elements

4. Elements found in Living Organisms
98 % of living mass composed of 4 elements
Oxygen
Carbon
Hydrogen
Nitrogen
Minerals
Trace elements

5. The Atom Basic Unit of Elements
Most fundamental unit of an element that retains the properties of the element
Structure determines properties of element
Composed of sub atomic particles

6. Subatomic Particles
Proton
Neutron
Electron

7. Protons Composed of quarks Positive charge of +1
2 ups and a down
Positive charge of +1
Mass of 1 AMU or Dalton
Resides in atomic nucleus
Confers identity
Atomic number

8. Neutrons Composed of quarks Electrically neutral Mass of 1 AMU
2 downs and an up
Electrically neutral
Mass of 1 AMU
Resides in atomic nucleus
Stabilizes atomic nucleus
Contributes to atomic mass
Number varies
Isotopes

9. Quarks and Leptons both Fermions

10. Isotopes Forms of an element that differ in the number of neutrons
Atomic mass changes but atomic number does not
May be radioactive if atomic nucleus is over crowded

11. Isotopes

12. Common Radioactive Isotopes

13. Electrons
Fundamental particle called a lepton
Electrical charge of -1
Mass negligible(1⁄1836 of that of the proton)
Located outside the atomic nucleus in the electron cloud
Neutralizes the charge of the protons
Participates in chemical bonding

14. Electron location within the Electron Cloud
Distance from atomic nucleus indicates electron energy level
The farther from the nucleus, the higher the energy
Levels called shells (1st quantum number,N)
Named as numbers (1,2,3…)
Maximum number of electrons in each shell= 2N2
Outer shell=valence shell
Outer shell electrons most readily available for chemical bonding

15. Electron location within the Electron Cloud
Orbitals (2nd quantum number (l)
Specific region in which an electron is likely to be found
Named with letters
s- sharp
p-principal
d- diffuse
f-fundamental
Named after groups of lines in the spectra of alkali metals

16. Electron location within the Electron Cloud
Shapes of orbitals
s spherical- 2 electrons
p party balloons- 6 e-
d complex 10 e-
f complex 14 e-
Energy increases from s-f
Electrons usually fill from s→f with some exceptions
3rd quantum number is the axis or magnetic orientation of the orbital (m)

17. Electron Fill Electron configuration of an element
Fill from lowest energy to highest energy location
Opposite spins for electrons in same orbital (Pauli exclusion principle)
Spin is the 4th quantum number (s)

18. Periodic table Periods Horizontal rows
Represent electron filling of a shell
Fill from left to right
s 1st 2 groups
p transition metal
d right block, metaloids, non metals
f lanthides and actinides

20. Electron configurationsLi Cl F Ne

21. Bohr Model C N O Li Cl F Ne

22. Chemical bonding Forms by interactions between valence shell electrons
Goal- full valence shell
Two main types
Ionic
Covalent
Type determined by electro negativity differential

23. Ionic Bonds Electron transfer Large electro negativity differential
Between metals and non metals
Ions formed
Cation
Anion
Attraction between oppositely charged ions

24. Covalent Bonds Electrons shared between atoms
Low electro negativity differential
Hybrid orbitals
Electron timeshare
Single
Double
Triple

25. Polar Covalent Bonds Electrons not shared equally Creates a dipole
Rotates in electrical field
Fosters dipole interactions

26. Non-Polar Covalent Bonds
No separation of charges
Equal electron sharing
Even distribution of charges
Fosters induced dipole interactions

27. Dipole Interactions Occur between polar covalent molecules
Stronger than interactions between non-polar molecules
Slightly negative region of one molecule is attracted to slightly positive region of a neighboring molecule
Cohesive

28. Hydrogen Bonds Special type of dipole interaction
Involves H as the slightly + component
Very significant in biological systems
2 strands of DNA
Protein shape
Genetic code

29. Induced Dipole Interactions
May be referred to as Van der Waals interactions
Very weak
Between non-polar covalent molecules
Volatility of non-polars compared to polars

30. Induced Dipole Interaction

31. Solubility Like dissolves like
Test for polar substance- dissolve in water
Non polar solvents clean non polar stains
Polar solvents clean polar stains
Oil and water