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Chapter Chapter 2

BIO SCI 93 Chapter Notes - Chapter Chapter 2: Ionic Bonding, Hydrogen Bond, Valence Electron

Biological Sciences
Course Code
Jorge Busciglio Kim Green Marcelo A Wood
Chapter 2

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Chapter 2: cont.
Matter- anything that takes up space and has mass
o Made up of elements- substance that can’t be broken down to other substances by
chemical reactions (periodic table)
Compound - substance consisting of 2+ different elements combined in a fixed ratio
Oxygen, carbon, hydrogen, and nitrogen make up 96% of matter
Essential elements - organisms need to live healthy life + reproduce (ie. oxygen, carbon etc)
Trace elements - required by an organism in any minute quantities
Atom is the smallest unit of matter that still retains the properties of an element
Subatomic particles - protons, neutrons, electrons
…(rest on notebook)
Ions: the resulting oppositely charged atoms (or molecules) after the more electronegative atom
strips an electron away from the other
Cation: positively charged ion
Anion: negatively charged ion
Ionic bond occurs when cations and anions attract each other
Transfer of an electron is not by itself the formation of a bond but rather it allows a bond to form
because it results in ions.
Compounds formed by ionic bonds are called ionic compounds or salts.
Ionic compounds do not consist of molecules
Ion also applies to entire molecules that are electrically charged.
Weak chemical bonds: hydrogen bonds and van der Waals interactions
Hydrogen bonds: attraction between a hydrogen and an electronegative atom
o When a hydrogen atom is covalently bonded to an electronegative atom the hydrogen
atom has a partial positive charge that allows it to be attracted to different electronegative
atom nearby
Electrons are not always evenly distributed (even in nonpolar bonds). Electron may accumulate in
one part of a molecule or another - results in van der Waals interaction
Molecules consisting of two atoms are always linear
Atoms with valence electron is both s and p orbitals often form the geometric shape of a
tetrahedron, a pyramid with a triangular base.
Chemical reaction - making and breaking of chemical bonds, leading to changes in the
composition of matter (reactants to products)
Matter is conserved in a chemical reaction - reactions cannot create or destroy atoms but can only
rearrange the electrons among them
All chemical reaction are reversible
Concentration affects reaction - more one side is concentrated the more it will react
Eventually will reach chemical equilibrium where concentration of products and reactants have
stabilized at a particular ration (equilibrium does not mean concentration is equal)
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