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Define: Qualitative Analysis
Testing an entity to determine the chemical contituants - what's in it?
Define: Quantitative Analysis
Measurment of the quantity of a chemical entity - how much of something is in it?
The ability of a substance to conduct electricity, a physical property of matter.
A compound that, when dissolved in water, produces a solution that conducts electricity.
Define: Non Electrolyte
A compound that, when dissolved in water, does not create a solution that conducts electricity.
Define: Octet Rule
Atoms gain or lose electrons in their outer most shells in order to attain a noble gas configuration.
An atom, or group of atoms, that has lost or gained one or more electrons.
An atom that carries an overall negative charge because it has more electrons than protons.
An atom that carries an overall positive charge because it has more protons than electrons.
Define: Valence Electrons
Electrons found in the outermost shell of an atom.
Define: Lewis Symbol
A diagram composed of a chemical symbol and dots, depicting the valence electrons of an atom.
Define: Monatomic Ions
An ion that is composed of only one atom.
Define: Polyatomic Ion
An ion that is composed of two or more atoms.
Define: Ionic Bonds
The bond that results from the electrostatic force of attraction that holds positive and negative ions together.
Define: Ionic Compound
A compound that consists of cations and anions held together by ionc bonds.
Define: Ionic Crystals
A solid that consists of large number of cations and anions arranged in a repeating 3D pattern.
Define: Formula Units
The smallest amount of a substance having the composition given by its chemical formula.
Small indivisible particles that have all the properties of the element they make up.
A substance comprised of only one type of atom.
An atom that contains the same number of protons but a different number of neutrons.
ex: Cl-35 and Cl-37 are two naturally occurring isotopes of Cl. Both have 17 protons but Cl-35 has 18 neutrons while Cl-37 has 20 neutrons
Democratus - 2000BC
First to suggest that all matter is composed of tiny particles - atoms
Dalton - 1804
"Billiard Ball Model"
- Elements are compost of identical indivisible atoms.
- Discovered subatomic particles showed that atoms were not indivisible.
J.J. Thomson - 1900
"Raisin Bun Model" or "Plum Pudding Model"
Revised Dalton's model
- An atom can be described as a sphere of positive electricity in which negative electrons are embedded like raisins in a bun.
- Most of the mass of the atom is associated with the positive electricity.
Rutherford - 1912
"Gold Foil Experiment"
- Atom has a nucleus in which its positive charge (protons) & mass are concentrated.
- The majority of the atom's volume would be empty space occupied only by moving negatively charge electrons.
- - The existance of uncharged particles (neutrons)
Rutherford's Gold Foil Experiment
- Experiment:Shot a beam of positively charged subatomic particles of radioactive Polonium (Po) at a piece of gold foil contained within a circular florescent screen.
- Majority of protons passed through the gold foil uninfluenced, but 1 in every 10,000 experienced some kind of change in their path of travel. Thus, since some of the protons were deflected, there must be an area in the atom with a large positive charge (the nucleus)
Bohr - 1913
"Orbit Model" or "Solar System Model"
- Carried out the flame test of the elements & explained that the different colours that resulted were due to the position of the electrons around the nucleus of the atoms.
- Electrons curcle the central nucleus in orbits (energy levesl) called shells.
- Each shell is a different distance from the nucleus.
- - Each shell has a maximum number of electrons that it can hold.
- 1st: 2
- 2nd: 8
- 3rd: 8
- 4th: 18
Quantum Mechanical - 1920s
Mostly supports Bohr except:
- Electrons do not exist in fixed orbits / do not have a fixed or definite path. May exist anywhere within an electron cloud.
- Determining exactly where an electron will be at any given moment is very difficult and can only be theorized using mathematical equations.
Structure of the Atom
Three types of particles:
- ( + ) or ( p )
- - Found in the nucleus (center) of the atom & have a charge of +1.
- - Particles are very dense and have a large mass compared to electrons.
- ( 0 ) or ( n )
- - Found in the nucleus of the atom and have a charge of 0.
- - Have the same mass as protons.
- ( - ) or ( e )
- - Found in shells or orbits surroundign the nucleus and have a charge of -1.
- - Have a small mass.
- - In a neutral atom, are equal to the number of protons in the nucleus.
- Makes the element unique & is equal to the number of protons in the nucleus.
- In a neutral atom, it is also equal to the number of electrons in the shells.
- - In the periodic table, this number is usually found in the upper right corner of the element box (whole number)
- Is equal to the number of protons and neutrons combined (p + n = mass)
- Usually found in the bottom of the element box as a decimal.
Atomic Mass Unit - unit of measurement
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