Introduction to Chemistry
CHEMISTRY
Matter occupies space and has mass
Elements - 92 naturally occurring substances
fundamental substance that cannot be broken down to a different substance
ORGANIZATION OF MATTER
Most of the human body is made up of only four kinds of elements
HYDROGEN--------- H
CARBON------------- C
NITROGEN---------- N
OXYGEN-------------- O
TRACE ELEMENTS
P-----------Phosphorus
Mg---------Magnesium
K-----------Potassium
Ca---------Calcium
Cu---------Copper
S-----------Sulfur
Fe----------Iron
I------------Iodine
Na---------Sodium
Cl----------Chlorine
COMPOUNDS
two or more elements combine
ex: H20 C6H12O6 H2SO4
atoms--smallest unit of matter that is unique to a particular element
subatomic particles
protons
neutrons
electrons
ATOMS
atomic number---number of protons
atomic weight---protons + neutrons
atomic charge---protons - electrons
ELECTRON SHELLS
Electrons exist in specific numbers at certain distances from the nucleus of an atom
electron shells or orbitals
1st orbital = 2 electrons
2nd orbital = 8 electrons
3rd, 4th, 5th etc
ISOTOPES
isotopes--atoms in which the number of neutrons are different from the number of protons
C12 = 6 protons + 6 neutrons
C14 = 6 protons + 8 neutrons
RADIOISOTOPES
Radioisotopes-radioactive isotopes
unstable, tend to break apart (decay) into more stable atoms
used in fossil dating and as medical tracers
IONS
Ion--atoms which have lost or gained electrons and thus gained a positive or negative charge
ex: Na+ 11 protons 10 electrons
ex: Cl- 17 protons 18 electrons
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http://www.pbs.org/wgbh/aso/tryit/atom/builder.html
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CHEMICAL BONDING
union of the electron structure of atoms to form molecules (compounds)
1) Ionic bonding
2) Covalent bonding
3) Hydrogen bonding
IONIC BONDING
bond formed between ions due to their mutual attraction of opposite charges
ex: Na+ and Cl-
form NaCl (table salt)
COVALENT BONDING
electrons are shared
ex: H-H O=O N N
H2 O2 N2
1) Non-polar covalent
2) Polar covalent
NON-POLAR
COVALENT BOND
1) Non-polar covalent bond
electrons are shared evenly
ex: H-H
H2
COVALENT BONDING
2) Polar covalent bonding
electrons are more attracted to one atom than another
ex: O H H
electrons are more attracted to oxygen than hydrogen
electrons spend more time around oxygen than hydrogen
HYDROGEN BONDING
hydrogen atom reacts weakly with another atom or molecule bonds are easily broken
ex: water molecules are held together by hydrogen bonds
ex: DNA--strands are held together by hydrogen bonds
PROPERTIES OF WATER
H 2O carries a partial charge
due to the extra amount of time that the electron (in its figure eight pattern) spends around oxygen
PROPERTIES OF WATER
Hydrophilic- (water loving) polar substances
able to mix with water
water-----sugar
Hydrophobic- (water dreading) non-polar substance
unable to mix with water
water----salad oil
PROPERTIES OF WATER
water acts as a solvent
Na+ Cl- dissolved in water
salt is the solute and water is the solvent
ACIDS, BASES, AND SALTS
ACIDS
Substances dissolved in water release a proton (H+)
HCl
BASE
substances dissolved in water release a hydroxide ion (OH-)
NaOH
SALTS
precipitate formed by the reaction of an acid and a base
NaCl
pH SCALE
measures the concentrations of free H+ ions
0-----------------------7--------------------------14
acid base
pH of 7
the concentration of H+ ions and OH- ions are equal to each other
ex: water
the greater the H+ ions the lower the pH