3-1 Atomic Theory of Matter
Atoms, Elements, and Compounds
Structure of Atoms
Atoms, Elements, Compounds
Basic chemistry is needed
Building blocks - atoms
Elements - only one kind of atom
112 different elements
two or more kinds of atoms combined in definite proportions
O 2, C O 2
Shorthand and symbols
first letter capitalized
second letter lower case
Look at figure 3-3 page 35 of text
Structure of Atoms
2500 years ago, ancient Greece
recent research finds atoms consisting of smaller particles
protons, + charge, inside nucleus, mass = 1 amu
neutrons, no charge, inside nucleus, mass = 1 amu
atomic number = number of protons
mass number = sum of protons + neutrons
electrons, - charge, outside nucleus, mass less than + or neutron
Atoms of an element may have different numbers of neutrons.
Are not exactly alike
behave the same chemically
all elements have isotopes
same atomic number, different mass numbers
16O, 17 O, 18 O or Oxygen - 18
Isotope nuclei are unstable
emits charged particles
radiation that can not be predicted
Radioactivity = nuclear process
discovered in 1896
elements of Uranium
detect abnormalities, treatment cancer, study chemical reactions ( tracers )
Oxygen - 18 not radioactive
study process of photosynthesis
3-2 Chemical Bonding and Chemical Reactions
Sharing of a pair of electrons by two atoms creates a force of attraction that holds the atoms together.
When a chemical bond is formed by sharing of electrons, it is covalent.
Electron structure of elements
oxygen, 8 protons, 8 electrons, 8 neutrons
O2 , double bond
H, O, N, Cl, F
Ion - atom that has an excess charge
Ionic bond - the force of attraction between two ions.
Na + Cl2 -----> 2NaCl
Na, 11 protons, 11 electrons ( + 1 )
Cl, 17 protons, 17 electrons ( - 1 )
Sodium Chloride - crystal form
Every compound consists of atoms combined in definite proportions.
Glucose = C6H12O6
Is a kind of chemical formula
shows only the number and kind of atoms in a molecule but also how the atoms are bonded together to one another.
H - C = C - H Acetylene, triple bond
go to page 43 of the text
Chemical bonds can be broken
atoms can form new bonds in new combinations
arrow -----> means produces or yields
example: hydrogen + oxygen -----> water
H2 + O2 -----> H2O
balance the above equation ( page 44 )
Law of Conservation of Mass
States: that mass can be neither created nor destroyed in chemical reactions.
Because atoms have mass.
They are just rearranged.
A balanced equation for the breakdown of glucose.
C6H12O6 + 6O2 -----> 6CO2 + 6H2O
different substances retain physical properties
Sodium chloride and iron fillings
Homogeneous mixture - same throughout
N, O, CO2, water vapor and others
heterogeneous mixture - different throughout
Any homogeneous mixture can be called a solution
used for mixtures that are liquids.
solvent - dissolves the solute
solute - dissolved in the solvent
may be solids, liquids, or gases
most common solute is water
dissociation - breaks into sodium and chlorine ions
NaCl -----> Na+ + Cl--
A mixture that separates on standing
sand in water
shake the container of sand and water, let the container sit for a period of time, the sand will settles out.
Gravity will cause the sand to settle.
Another type of mixture
the particles are larger than the molecules or ions but too small to settle out.
Medium does not to be a liquid, can be a gas or solid.
smoke - carbon dioxide in air.
Milk, mayonnaise, whipped cream ( gas in a liquid )
Any compound that produces hydrogen ions in solution.
Hydrogen covalently bonds to another atom or group of atoms.
HCl - hydrochloric acid
important to life activities
dissolved in water: HCl -----> H+ + Cl--
Compounds that produce hydroxide ions when dissolved in water
dry state many are ionic compounds
NaOH - sodium hydroxide
NaOH -----> Na+ + OH --
Process of reacting an acid and a base to produce a neutral solution.
Neither an acid or a base.
H + + OH - ----> HOH ( or H2O )
Acid neutralizes a base
Base neutralizes an acid
Ionic compound produced from neutralization reaction between and acid and base
NaCl = Sodium Chloride
HCL + NaOH -----> Na + + Cl - + HOH
Hydrochloric acid plus sodium hydroxide yields sodium plus chlorine and water.
Provides essential ions for body processes
The pH Scale
pH = power of Hydrogen
acids = very acidic 0 to 6.9
neutral = 7.0
base = 7.1 to 14 very basic
indicators - shows acid, base, neutral, actual pH value
litmus paper, red and blue
methyl orange = turns yellow to red ( moderate acid )
phenolphthalein = turns red ( base )
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