Chapter 2- Concept 2.1: Matter-Organisms are composed of matter-It has three forms-Solids-Liquids -Gases- Elements and Compoundso Elements: is a substance that can not be broken down further. Ex: Sodiumo Compound: Substance consisting of two or more elements in a fixed ratio. Ex: Sodium chloride.- Elements of lifeo 20-25% of the 92 elements are essential to life.o C, H, O, N make up about 96% of living matter.o Trace Elements: required by an organism in minute quantities.- Concept 2.2: Structure of an Atomo Neutrons: No Chargeo Protons: Positive Charge, also determines Atomic Numbero Electrons: Negative Charge- Subatomic Particleso Proton Mass and Neutron mass are measured in Daltons 1 Dalton = 1 amuo Electrons form a cloud around the nucleus When electrons and protons are equal the atom is neutral.- Atomic Number and Atomic Masso Atomic number is the amount of protonso Atomic mass is neutrons + protons.o Isotopes are when there are more neutrons than protons- Electron Distributiono Valence Electrons are the electrons in the outermost shell or valence shells.o Electrons with a full valence, noble gases, are inert.o Orbitals are where electrons can be found 90%- Chemical Bondso Covalent (O2) Two elements share electrons Single Bond is a sharing of one pair of electrons Double Bond is sharing of two pairs of electrons Bonding capacity is determined by an atoms valence electrons Electronegativity is an atoms attraction for electrons in acovalent bond. (Oxygen and Nitrogen are very electronegative) Non-polar covalent bonds occur when electrons are distributed evenly. Polar covalent bonds occur when one atom is more electronegative than the other which causes a partial positive (d+) or negative (d-) charge for each atom or moleculeo Ionic (NaCl) Form when atoms give up electrons, each atom becomes an ion. Cation: Positive Ion Anion: Negative Iono Weak chemical Bonds Hydrogen Bonds When a hydrogen atom covalently bonded to oneelectronegative atom is also attracted to another electronegative atom Van der Waals interactions Attractions between molecules that are close together as a result of these charges Important in maintaining the structure of proteins and DNA- Molecular Shape and Functiono Atoms shape is very important to its functiono A molecule’s shape is determined by the positions of its atoms’ valence orbitalso Biological molecules recognize and interact with each other with a specificity based on molecular
View Full Document
Unlocking...