U of S. Carolina – Chemistry 105 – Test 2 Flashcard

Name of Element that is Named After Mary Cluric
Polonium
Henri Becquerel (1896)
Experimented with phosphorescence of certain materials (uranium)
Earnest Rutherford (1899)
Found that alpha rays could be stopped by thin pieces of paper. Whereas beta rays were only stopped by at least 0.5 cm of lead
Paul Villard (1900)
Discovered the high energy, extremely penetrating gamma ray having characteristics of light waves. Very damaging to human tissue
Madame (Marie) Curie
(1859-1906)
Won the noble prize along with Henri Bacquerel for their work on radioactivity

She discovered that some elements are more radioactive than others

Radioactivity
The result of a natural change of an isotope of one element into an isotope of a different element resulting in a nuclear reaction
Nucleons
Protons and Neutrons

During a nuclear reaction the number of nucleons is conserved but the identity of the element changes by emitting a particle or a ray

Alpha Emitters
Radioactive decay of an atom resulting in the release of an Alpha particle ad changing the identity of the atom
Alpha Particle
Helium Nuclei (He)

Decreases an element’s electrons by 2
Decreases an element’s atomic mass by 4

Beta Emitters
Radioactive decay of an atom resulting in the release of a Beta particle and changing the identity of the atom
Beta Particle
An electron

Adds 1 electron to an element

Gamma Rays
Highly energetic protons that is released by the excess energy remaining after a nucleus emits an alpha or beta particle
Positron Emission
A proton is converted to a neutron

An element loses 1 electron

Stability of Atomic Nuclei
Based on relative number of protons and neutrons
*Mass number as least twice as large as the atomic number (with the exception of Hydrogen isotopes)
**When a greater neutron/proton ratio exists (beta decay occurs)
**When a greater proton/neutron ratio exists (positron emission occurs)
**For elements greater than atomic number 83 (alpha emission occurs decreasing the number of protons and neutrons by 2)
Half Life
The time required for exactly 50% of the original material to decay
Radio Carbon Dating
Determining the age of a sample using the carbon-14 isotope
Gamma Rays (Applications of Radioactivity)
From cobalt-60 and cesium-137 are used to irradiate food
Food Radiation
Retards the growth of organisms such as molds, bacteria, and yeasts
Two Ways Radioactive Isotopes Are Used
Diagnosis and Therapy
Diagnosis
Radioisotopes are inserted into the patients body allowing an image to be produced of the problem area
Fission
Large amounts of energy are released when heavy atomic nuclei split
Fusion
Large amounts of energy are released when small atomic nuclei are combined
*Releases as much energy as fission with fewer radioactive by-products
Octet Rule
In forming bonds, main-group elements gain, lose, or share electrons to achieve a stable electron configuration with eight valence electrons
Ionic Bond
The attraction between positive and negative ions
Ionic Compounds
Compounds composed of positive and negative ions
Formula Unit
In ionic compounds, the simplest ratio of oppositely charged ions that gives an electrically neutral unit
Lewis Dot Symbols
The valence electrons, represented by dots, are placed around the symbol until they are used up or until all 4 sides are occupied

**Can be used along with the octet rule to predict formulas for ionic compounds

Binary Compound
Chemical compound composed of one metal and one non-metal
**Cation = metal = common name
**Anion = non-metal = name ends in -ide

Example: NaCl Sodium Chloride

Polyatomic Ion
A group of atoms with a net charge that behaves as a single particle
Covalent Bond
A bond in which 2 atoms share electrons to achieve a noble gas configuration
Lewis Structure
Electron dot representation of valence electrons in a molecule
Bonding Pair
Pair of electrons shared between 2 atoms in a molecule
Nonbonding Pair
Unshared pair of valence electrons in a molecule
Hydrocarbons
Compounds containing only carbon and hydrogen
Alkanes
Hydrocarbons with carbon-carbon single bonds
Saturated Hydrocarbons
Hydrocarbons that are alkanes
Double Bond
A bond in which 2 pairs of electrons are shared between atoms
Triple Bond
A bond in which three pairs of electrons are shared between atoms
Electronegativity
The ability of an atom to attract electrons toward itself
**Increases from left to right on the periodic table and from top to bottom
Non-Polar Bonding
Describes a bond or molecule in which charge is evenly distributed, with no positive or negative regions
Polar Bonding
Describes a bond or molecule in which charge is unevenly distributed, creating positive and negative regions. Based on differences in electronegativity
Shapes of Molecules
Determined from the number of bonding pairs and the number of Ion pairs on the central atom
Electrolyte
A compound that conducts electricity when melted or dissolved in water
Non-Electrolyte
A compound that does not conduct electricity when melted or dissolved in water, or does not separate into ions in water
Intermolecular Forces
Attractive forces that act between molecules; weaker than covalent bonds
Dipole-Dipole Forces
Attractive forces between polar molecules
London Dispersion Force
*Very weak small molecules
*Very strong large molecules
*All molecules contain it
Hydrogen Bonding
Attraction between a hydrogen atom bonded to a highly electronegative atom (O,N,F) and an electronegative atom in another or the same molecule
Solids
Fixed shape and fixed volume, non-compressible, very strong intermolecular forces
Liquids
Variable shape but fixed volume, strong intermolecular forces, non-compressible
Gases
Variable shapes and volume, compressible, weak intermolecular forces

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