Properties of Matter, Elements,

Compounds, and Bonding.

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Chemical Properties.A chemical change pemanantly changes the conpound into another.Basic unit of matter is an atomSubatomic particles- protons (+), neutrons, and electrons (-)

AtomsProtons neutrons in the nucleusElectrons travel around the nucleus in orbits or clouds or levels of energy.Atom is neither positive or negative in charge - it is neutral.ION- An atom that has lost or gained an electron(s)

Identifying ElementsAtomic number- number of protonsThe number of protons (atomic number) determines the identity of an elementAn element- only one type of atomRepresented by a chemical symbol such as O for oxygen or Na for sodiumCHNOPS- Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorous, Sodium main elements of human body

IsotopesAtoms of the same element that have a different number of neutronsMany (not all) are unstable and break down, emitting energy – radioactive isotopesUsed for determining the age of fossils, treatment of diseases, and even to sterilize food.

Chemical CompoundsCompounds- Chemical combination of

two or more elements Represented by a chemical formula that indicated the elements in the compound and their proportions.

Chemical BondingIn order to become stable, an atom will either gain, lose, or share electrons. Each level can hold only a certain number of electrons. (2,8,8)Ionic, covalent, and polar covalent bond

Covalent BondingEqual Sharing of electronsEach atom fills it’s outermost energy levelSmallest particle of a compound is a molecule

Ionic BondingAn ionic bond forms when one atom gains electrons and the other loses electronsIons are held together by their opposite chargesInvolves atoms of very different sizes

Chemical reactionsThe making or breaking of bonds is called a chemical reactionReactants (chemicals that enter a reaction) & products (compounds that are produced)A chemical reaction is indicated by a chemical equation.Na (+) + Cl (-) ---> NaClO2 + 2H2 2H2O

Polar CovalentThe unequal sharing between two atoms (usually one much larger than the other)Creates slight charge on either side of the molecule.

Hydrogen bondBetween hydrogen and another atom such as nitrogen or oxygenWeak attractive force that forms temporary, easily broken bonds

Waterimportance for living things

Water has an unusual chemical structureWe are over 70% water

Properties of water1. less dense as a solidFound in all three states (solid, liquid and gass) on the earth

2. Water is a good solvent. Many compounds dissolve in water.3. Water is slow to heat and slow to cool.4. water is cohesive – water molecules will attract other molecules5. water is adhesive- water adheres to other molecules

Why?The bonds are covalent, but the sharing is unequalThe water molecule carries a slight chargeIt is polar

Hydrogen BondsThe slight charge attracts other water moleculesThis forms weak temporary hydrogen bonds

As water changes state it adds or breaks apart hydrogen bonds. This slows changes in temperature

solventSome hydogen bonds will pull strongly enough to break off a hydrogen ionH2O H(+) + OH (-)This will ionize a small portion of the water creating equal numbers of hydrogen and hydroxide ions solution (solute and solvent) NaCl Na+ Cl -

PHIn a liter of water only 0.0000001 m/l of water has ionized. (That’s 1x10 ^-7) (PH=7)PH stands for the percent of hydrogen ions in solution in relation to hydroxide ions

More hydrogen ions are added the ph will go down (example hcl)If more hydroxide ions (OH) are added then the PH wil go up (example. NaOH)