Transcript
Levels of Biological Organization
atom
molecule
cell
tissue
organ
organ system
organism
Basic Chemistry (Inorganic)• Atom
– Atoms are the basic units of elements– 96% of human body: OCHN
Periodic Table of The Elements
– Each atom consists of a nucleus and orbiting electrons
Helium (He)
nucleus
electron
• Nucleus– Proton: “+” charged, atomic mass = 1 unit– Neutron: uncharged, atomic mass = 1 unit
• Electron shell– Electrons: “-” charged, atomic mass 0 unit
Atoms are electrically neutral
Atomic mass = proton mass + neutron mass
Atomic number = the number of protons
All atoms of an element have the same number of protons
atomic mass 4
atomic number 2He atomic symbol
– Isotopes• Atoms of the same element that differ in the
number of neutrons
126
Carbon 12C
136
Carbon 13C
146
Carbon 14C
(radioactive)
147
Nitrogen 14Ndecay
– Electron shells• The innermost shell holds up to 2 electrons.• The outermost shell (valence shell) is most
stable with 8 electrons (rule of eights)
• Chemical bonds– Ionic bond
Electrons are transferred from one atom to another• Anion: gain electrons, negatively charged• Cation: lose electrons, positively charged
– Covalent bond: share electrons between atoms to meet the rule of eights
hydrogen gas (H2)
oxygen gas (O2)
water (H2O)
nonpolar
polar
– Hydrogen bond: attraction between electropositive H and electronegative O or N.
polar molecule
• Properties of H2O: all attribute to hydrogen bond
– High heat capacity: • Water temperature rises and falls slowly
– High heat of vaporization: • Vaporization of water requires lots of heat
– Solvent:• Dissolves ionized and polar molecules
– Cohesive and adhesive:• Water molecules adhere to each other and polar surfaces
– High surface tension:
– Ice is less dense than liquid H2O
• BufferA chemical or a combination of chemicals that keeps pH within normal limits, usually weak acids or weak bases.
– Acids • Dissociate in water and release H+
• Strong acid: Dissociation is almost complete.HCl → H+ + Cl-
• Weak acid: Dissociation is minimal.
(carbonic acid) (bicarbonate ion)H2CO3 H+ + HCO3
-
– Bases • Either take up H+ or release OH-
• Strong base: Dissociation is almost complete
NaOH → Na+ + OH-
• Weak base: Dissociation is minimal
ammonia ammonium ion
NH3 + H2O NH4+ + OH-
– pH scale• Measurement scale for hydrogen ion concentration
• pH = -(log10 [H+])
0 7 14acid base
[H+](moles per liter)
pH
1 x 10-6 6
1 x 10-7 7
1 x 10-8 8
Study Guide• Which four element make up the bulk of living matter?• Name the elements: O, C, H, N, Ca, P, K, Na, Cl, I, Fe.• What is the nucleus of an atom composed of?• What type of charge do protons carry?• Do neutrons have charge?• What type of charge do electrons carry?• What is the atomic number?• What is the atomic mass?• What are isotopes?• An atom is inert when its valence shell contain ____ electrons.• What type of chemical bond exists in table salt (NaCl) and O2?• What type of chemical bond contributes to the special properties of
water?• What is the scale of pH? What pH is acidic? What pH is alkaline?
top related