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Chapter 2: Chemical Context - Coggle Diagram
Chapter 2: Chemical Context
2.1 Matter
Made up of elements
Element: pure substance
92 elements
20-25% are essential elements
Necessary elements for an organism
Compounds: 2 or more elements
NaCl
Water
Trace elements
Small amounts required
Evolution of tolerance
species adapted
Takes up space, has mass
Metals
Gases
Oils
Living Organisms
Rocks
2.4 Chemical Reactions
Reactions
Cannot create/destroy
Rearrange electrons
Photosynthesis
takes place in green plant tissue
example of matter rearrangement
foundation of life in most ecosystems
sequence of many chemical reactions
Products
resulting materials
Theoretically reversable
two opposite-headed arrows
products become reactants, vice versa
Reactants
starting material
Reactant concentration
greater concentration
molecules collide frequently
react and form products
same with products
products accumulate
frequent reverse reactions
Chemical Equilibrium
state in which the rate of the forward reaction equals the rate of the reverse reaction
stabilized concentration at a ratio
does
not
mean reactant & products are equally concentrated
affects reaction rate
Chemical Reactions
Making/breaking bonds change composition in matter
2.2 Element's Properties
Isotopes
same # of protons, more neutrons
radioactive isotope
unstable isotope
half-life
50% of parent isotope decays
radiometric dating
method to find the age of rocks/fossils
Atomic Number/Mass
atomic #: # of protons
mass # = # of protons + # of neutrons
Energy Levels
Energy: capacity to cause change
Potential energy:
energy resulting from the location
more distance from nucleus, more P.E.
electron absorbs energy, moves from nucleus
determined by energy levels
electron shell:
energy level
less distance, less P.E.
electron loses energy, moves to nucleus
Subatomic particles
electrons
negative charge
form 'cloud' around nucleus
protons
positive charge
in the atomic nucleus
1.7 x 10^-24 g
1 dalton
neutrons
no electrical charge
in the atomic nucleus
1.7 x 10^-24 grams
1 dalton
Chemical Properties
electron shells
1st shell holds 2 electrons
2nd shell holds 8 e
valence shell
valence electron
if complete, atom is inert (unreactive)
Atom
Smallest unit
mostly empty space
Electron Orbitals
orbital
where e is found 90% of the time
concentric circle
average distance
2.3 Molecules and Ionic Compounds
molecular formula
H_2
Covalent Bonds
chemical bond where atoms share a pair of valence electrons
molecule: atoms held together
electronegativity
attraction of a given atom
more electronegative, stronger pull on shared electrons
Nonpolar covalent bonds
electrons are shared equally between two atoms of similar electronegativity
Ionic compounds
ionic bonds are the strongest
are weak in water-based solutions
compound resulting from the formation of an ionic bond; also called a salt
Incomplete valence shells
Chemical bonds
share/transfer electrons
atoms stay together
covalent bonds are the strongest
bonds
double bonds
two covalent bonds
single bond
pair of shared electrons
atom's valence:
bonding capacity
compound
2 or more
different
elements
Ions
Anions
negatively charged ion
Atom that gained/lost e
Cations
positively charged ion
Ionic Bond
results from opposite charged ions attracting
Structures/Models
Structural Formula
H - H
the line is a single bond
Lewis dot structure
H:H
Space-filling model
most accurate representation
Weak Chemical Interactions
Hydrogen Bonds
when a hydrogen atom, which is covalently bonded, is attracted to another electronegative atom
Van der Waals
attraction between molecules or parts of molecules that are close
Ionic bonds in water
Shape and Function
Size
Shape
Tetrahedron
Linear
V-shaped
Determines how molecules respond/recognize