chem intro

7/23/2019 Chem Intro

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Elementsare made of a single kind of atom

and cannot be broken down by chemical means intosimpler substances.Atomsare composed of protons, neutrons, and electrons.Smallest part of an element that has the property of

that element.Compoundsare substances consisting of 2 or more elementscombined in a fixed ratio. Compounds can be separate

elements that make them up.

Elements and Atoms



ElectronsElectronsmove about the nucleus in orbitals.

Anorbitalis a three-dimensional region around a nucleus thatindicates the probable location of an electron.



IsotopesAtoms of the same element that have a differentnumber of neutrons are calledisotopes.



Ionic BondsAnionic bondis formed when one atom gives up an electron toanother. The positive ion is then attracted to a negatito form the ionic bond

.



Oxidation Reduction ReactionsA chemical reaction in which electronsare exchanged between atoms is called an

oxidation-reduction reaction.



Covalent BondsAcovalent bondis formed when two atoms

share electrons.



Hydrogen Bonding

Ahydrogen bondis the force of attractionbetween a hydrogen atom with a

partial positive charge andanother O or N with a partial orfull negative charge.



Water is considered to be apolarmolecule due to an uneven distribution of charge.

The electrons in a water molecule are sharedunevenly between hydrogen and oxygen.

The polarity of water makes it effective atdissolving other polar substances such as sugars, ionicompounds, and some proteins



Hydrogen bonds are classified

asweak bondsbecause they are easily andrapidly formed and broken under

normal biological conditions.Hydrogen bonds have polarity.One example involves thehydrogen bonding between watemolecules.



Cohesion and Adhesion

Cohesionis an attractive force that holdsmolecules of a single substance together, sucwater molecules.

Adhesionis the attractive force between twoparticles of different substances, such as watmolecules and glass molecules.



The cohesive forces between liquid molecules are responsiblefor the phenomenon known as surface tension. The molecules at t

surface do not have other like molecules on all sides of them andconsequently they cohere more strongly to those directly associaton the surface. This forms a surface "film" which makes it moredifficult to move an object through the surface than to move it whcompletely submersed.



Acids and Bases

Ionization of Water

Water ionizes intohydronium ions(H3O+) andhydroxide ions(OH–).

AcidsAcidic solutionscontain more hydronium ions than hydroxideions.

BasesBasic solutionscontain more hydroxide ions than hydroniumions.



pHScientists have developed a scale for comparingthe relative concentrations of hydronium ions andhydroxide ions in a solution. This scale is called the pH sand it ranges from 0 to 14.



All organic chemistry is based upon unique

properties of the carbon atom.



Isomerization-same molecular formula, but differentstructure. Also creates different properties for the molecu

The number of possible isomers increases rapidly as the

length of the chain increases

n-butaneisobutane



Isomers



Isomers

Pentose



Pentose

chem intro

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