1 / 55

Chapter 2: The Chemical Context of Life

Chapter 2: The Chemical Context of Life. Matter. Anything that has mass and occupies space. Smallest particle of an element (still retains elemental properties). Atom. Element. Matter made up of only one type of atom. 92 natural elements. Each element has a symbol.

marcos
Download Presentation

Chapter 2: The Chemical Context of Life

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 2:The Chemical Context of Life

  2. Matter • Anything that has mass and occupies space. • Smallest particle of an element (still retains elemental properties) Atom

  3. Element • Matter made up of only one type of atom. • 92 natural elements. • Each element has a symbol.

  4. Compound • Compound - Elements combined in fixed ratios. • A compound has characteristics beyond those of its combined elements.

  5. Question? • What elements are necessary for life? • Life requires about 25 chemical elements.

  6. Macroelements • Elements needed in large amounts or quantities. • Macro = Large • Examples: C HOPKNS CaFe Mg NaCl

  7. Microelements • Elements needed in very small quantities. • Also known as trace elements. • Micro = small • Examples: Cu, Co, Zn, Mo, I, Mn

  8. Atomic Subparticles • Protons + charge, 1 Dalton mass • Neutrons no charge, 1 Dalton mass • Electrons - charge, essentially no mass

  9. Atomic Model

  10. Atomic Number • The number of protons in the nucleus. • Each element has its own atomic number. • If you change the atomic number, you no longer have the same element.

  11. Atomic Mass • The number of protons and neutrons in the nucleus. • The atomic mass can change.

  12. Isotopes • Atoms of the same element with different atomic mass • Caused by changes in the number of neutrons • Used as “tracers”, used to kill cancer/bacteria cells, used to determine age of fossils/geological formations

  13. Types of Isotopes • Radioactive • Where the nucleus decays spontaneously, giving off particles and energy. • Heavy • Has a stable nucleus, but masses more than the standard isotope for the element.

  14. Energy • The ability to do work • THINK = ATP • ATP is how living organisms have the ability to do work • They USE ATP!!!

  15. Potential Energy • Is the energy that matter stores simply because of its position or location • Electrons have potential energy because of their position relative to the nucleus

  16. Electron Energy Levels • Energy levels around the nucleus of an atom • 1st level can have 2 electrons and has the lowest potential energy • Other levels can hold more than 2 electrons and have higher energy levels

  17. Electron Orbitals • The three dimensional space where an electron is found 90% of the time. • Different orbitals have different shapes. • Each orbital can hold only 2 electrons.

  18. Electron Orbitals

  19. Chemical Behavior Of An Atom • Is determined by its electron configuration in the energy levels and orbitals • This determines who is can bond with (if anyone!)

  20. Valence Electrons • The electrons in the outermost energy level • Electrons available chemical bonds • Atoms/Elements with same # of valence electrons will react similarly and will have similar characteristics

  21. Octet Rule • The most stable condition is to have an outer level of 8 electrons • Exception - 1st level is stable with only 2 electrons • When stable - no chemical reactions will take place • Ex: Ne, He, (Noble gases)

  22. Electrons of the first elements

  23. Chemical Bonds • Forces that join atoms together to form molecules • Usually caused by sharing or transferring valence electrons

  24. Bond Formation Depends On: • The number of valence electrons that must be gained, lost, or shared to reach the stable condition.

  25. Chemical Bond Types • Nonpolar Covalent • Polar Covalent • Ionic • Hydrogen • van der Waals forces

  26. Electronegativity • The attractiveness of a specific kind of atom towards e- in another atom • Important in covalent bonds • Periodic Table trend: • More electronegativity = stronger pull of e- • He has highest EN • Increases as you go right and up the table

  27. Nonpolar Covalent • When electrons are shared equally between atoms • Very strong bond • Important in many molecules found in living things • Ex: carbon to hydrogen, hydrogen to hydrogen, oxygen to oxygen

  28. Nonpolar Covalent • Can be single, double, or triple between two atoms • Each nonpolar covalent bond involves a pair of electrons

  29. Polar Covalent • When electrons are shared unequally between atoms • Results in “polar” molecules that have charged areas • Use δ symbol • Ex: Water, H to O bonds

  30. Ionic Bonds • Formed when electrons are transferred from one atom to another and ions are formed • Ex: NaCl • Why? Two atoms electronegativity are SO different that one atom gains e- completely

  31. Two Types of Ions • Cations - have lost electrons (p+ > e-) giving them a positive charge. • Ex: Sodium (Na+) • Anions- have gained electrons (p+ < e-) giving them a negative charge. • Ex: Chlorine (Cl-)

  32. Ionic Bonds • Formed when cations (+) and anions (-) attract each other • Weak chemical bond • Why? Environment easily affects strength of this bond • Ex: Salt  Solid in air/gas; Dissolves in liquid

  33. Ionic

  34. Hydrogen Bonds • When a hydrogen atom bonded to one molecule is attracted to the slightly negative area (often N or O) of another molecule • Very weak individual bond • Can be a “strong” force if there are many H bonds.

  35. Hydrogen bonds • Remember: • H bonds occur BETWEEN MOLECULES (not b/t atoms within ONE molecule) • Ex: H bonds hold water molecules together

  36. Hydrogen Bonds

  37. Van der Waals • Result of e- ability to move at high speeds • Creates “spots” where there are “pools” of + and – charges • Weak chemical “bond” • Ex: gecko’s feet

  38. Molecular Shape • Each molecule on Earth has a characteristic shape • Determined by the positions of the atom’s orbitals • Shape related to function

  39. Molecular Shape • Molecular shape is crucial because it determines how most molecules of life recognize and respond to one another. • Ex: • Viruses (reproduction), bacteria (reproduction), hormones/cell recognition

  40. Chemical Reactions • The making and breaking of chemical bonds • Reactions do not destroy matter, they only rearrange it

  41. Chemical Equations • A way to represent what is happening in a chemical reaction Ex: 2 H2+ O2 2 H2O

  42. Parts of the Equation • Reactants: - the starting materials • Products: - the ending materials • Note - all atoms of the reactants must be accounted for in the products 2 H2+ O2 2 H2O

More Related