Terms in this set (...)

Knowledge of the atom gives us the ability to
Predict properties of matter to develop useful products
Democritus (460-370 BC)
• Atoms cause the phenomena of nature

• All atoms are made of the same basic materials but different in side & shape

• Atoms cannot be further subdivided (Discontinuous Theory)
Aristotle (384-322 BC)
• Continuous Theory : No such things as atoms, lead arguments against it (this was rule for 2200 years)

• There are four elements : Earth, Air, Water, & Fire
Dark & Middle Ages
• Catholic Church controlled much of politics, economics, & science
- Atoms against the existence of God
• Aristotle's teaching were considered to be dogma (Church believed)
• Chemical methods described in writings
EX : Distillation, Metallurgy, & Mineralogy
- Emphasis on practical
• Theoretical speculation more frequent
• Pharmacists mainly responsible for the development of chemistry as an independent science
Francis Bacon (1561-1626)
• Heat is motion by very small particles

• Stressed the importance of experiment and inductive reasoning

• Necessary to pay attention to evidence that might contradict a held belief

• Insisted on facts (truth is not derived from authority)
Galileo (1564-1642)
The appearance of new substances in chemical changes involved the rearrangement of parts too small to see
Robert Boyle (1627-1691)
• Discovered the pressure/volume relationship of gases

• Physical phenomena can be explained in terms of matter in motion

• Properties of a substance are determined by the shape, number, & motion of particles which make it up
Lavoisier (1743-1794)
• First to use systematic names for elements/compounds

• Determined that combustion involved materials reacting with oxygen

• Realized the importance of very accurate weight measurements when studying chemical changes

• Proposed the Law of Conservation of Mass
Proust (1754-1826)
• Investigated quantitative aspects of compound formation

• Proposed the Law of Definite Proportions which states that the constituent element are always present in a definite proportion by mass
- EX : Copper Carbonate is always 5 parts copper & 4 parts hydrogen & 1 part carbon by mass
John Dalton (1766-1844)
• Father of modern chemistry

• Forcefully revived the idea of the atom as the fundamental particle of matter

• Did quantitative studies of different compounds
Dalton's Atomic Theory (1808)
1. All matter is made it very small particles called atoms

2. All atoms of one element are identical & have unique set of chemical properties, different from atoms of another element

3. Atoms are indivisible & don't disappear/appear & don't change into atoms of another element

4. Compounds are formed when atoms of two or more elements combine in a fixed ratio

5. Chemical reactions occur because of rearranging atoms
What does the Atomic Theory explain?
Law of conservation of mass & Law of definite proportions = Law of multiple proportions
The idea that atoms are indivisible was challenged by what areas of study?
1) Static Electric Charge

2) Radioactivity

3) Cathode Rays
Static Electric Charge
• Had been known about since ancient times

• Two types : Positive & Negative

• Law of Electrostatic Attraction states that like charges repel & opposites attract
• Spontaneous process in which some natural materials give off some penetrating radiations

• Discovered by Becquerel in 1896

• Studied extensively by Marie Curie who worked in his labs
Types of Radioactivity
• Alpha = Positive particles

• Beta = Negative particles

• Gamma = No mass (lights, x-rays)
Cathode Rays
• Produced in cathode ray tubes (CRT)

• Cathode = Negative Electrode
• Anode = Positive Electrode

• When voltage is applied, produces cathode ray & causes gases to glow/metals to heat. Bend towards a positive charge

• Forerunners of neon signs, TV, & fluorescent lights
What is a CRT
A partially evacuated glass tube with an electrode (piece of metal) sealed in each end.
Why did scientists question the idea that atoms were the smallest particle of matter that existed?
Evidence that :

1) Atoms can be divided & some spontaneously

2) Beta/Cathode ray particles 1/1836 times as massive as the smallest atom, must be subatomic
J.J Thomson (1897)
• Determined that the cathode ray is a stream of negative particles (electrons)

• Determined the charge to mass ratio
- 1.76 x 10^8 C/g (coulomb/gram)

• Used 20 different metals and got the same results

• Concluded that electrons are common to all those metals/gases & possibly to all atoms

• Proposed the plum pudding model of the atom
- Says the atom is a ball of positive charges with embedded negative charged particles
Robert Millikan (1909)
• Did the oil drop experiment
- Conclusion : Particles have some whole number of electrons attached

• Determined the measure of the charge on the electrons & mass
- 1.60 x 10^-19 C
- mass = 9.10 x 10^-28 g
E. Goldstein
• Used a CRT with a perforated cathode
- Found a different type of beam called canal rays which are positive charged particles (protons)
Ernest Rutherford (1910)
• Did the gold foil experiment
- Shot alpha radiation at a thin sheet of gold foil & most particles penetrated straight through
- However, ~1/8000 was deflected (some even directly back at source)

• Conclusion : The atom is mostly empty space with a very small dense & positive region containing most the atom's mass (it is called the nucleus)
• Stands for atomic mass unit
• Equal to 1.66 x 10^-24 g
• The nucleus has all the mass of the atom but very little volume
Atoms are neural this means that...
Protons = Electrons
Atomic Number
• Symbol is Z
• # of protons in an atom
• Identifies the element
Mass Number
• Symbol is A
• The mass of all protons * mass of all neutrons
• Atoms with the same # of protons (same element) but different number of neurons (different mass numbers)
- EX : C-12 (6 p+ & 6n•)
C-14 (6 p+ & 8 n•)
• Atoms with unequal # of protons & electrons

• Neg. Ions = Anions & have more electrons

• Pos. Ions = Cation & have more protons
Atomic Mass (Atomic Weight)
• Not the same as atomic/mass #

• Found on the periodic table (# that isn't whole number)

• The weighted average of all the isotope masses of an element

• Based on 1 amu being 1/12 the mass of a C-/12 nuclide

• Relative massed (Assigned to each element based on how they compare to a C-12 atom)
Group 1 elements
Alkali Metals
Group 2 elements
Alkaline earth metals
Group 7 elements
Group 8 elements
Noble gases
Polyatomic Ion
A group of atoms with an overall charge
Iconic Compounds
• Units are "formula units"
• 1 metal & 1 nonmetal
• Charges
• Structure is crystal lactic
Binary Naming
• 2 elements
• 1st cation & 2nd anion
• Change ending to "ide"
Ternary Naming
• 1st metal & 2nd polyatomic ion
Molecular Compounds
• Usually only involves non-metals
• Units = Molecules
Molecular Formula
Actual number and type
Empirical Formula
Lowest whole number ratio
Structural Formula
Diagram of compound
Naming molecular compounds
• 1st nonmetal : normal
• 2nd nonmetal : -ide ending
• Attach prefixes indicating number of atoms present (UNLESS first nonmetal has only one)
• Cation is hydrogen ion
• Anion varies
If anion is a single element naming
• Hydro________ic acid
• EX : HCL = Hydrochloric acid
If anion is polyatomic "-ate" naming
• Change "-ate" to "-ic"
• EX : H2SO4 = Sulfuric Acid
If anion is polyatomic "-ite" naming
• Change "-ite" to "ous"
• EX : H2SO3 = Sulfurous Acid