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

When was Radioactivity Discovered?
What is a Nuclear Change?
Involves changes in nuclear structure, such as fission (splitting) of a nucleus or an atom, or fusion (combining) of neutrons and protons to form heavier atoms. This involves about 1,000,000 times as much energy as a chemical change
Why do some atoms undergo radioactive decay and others don’t?
The atoms with unstable nuclei undergo change
Why are some radioactive isotopes more harmful than others?
Which radioactive by-product is most penetrating?
Gamma Rays
How is the nucleus of an isotope changed after beta decay?
It changes into a proton
The mass number of an isotope will decrease by 4 after which type of decay?
Alpha Decay
What is a Positron?
A particle equal in mass but opposite in charge to the electron
Who Discovered Gamma Rays?
Paul Villard
How long will it take for a 92 gram sample of copper-64 to decays to 23 grams, given the half life as 12.9 hours?
92/23 = 4
92x(1/4) = 23
2 half lives
2 x 12.9 = 25.8 hrs
Name two uses of radioisotopes?
Therapeutic and Diagnostic
With the half-life of about 6 hrs, how much Tc-99 would remain in a person’s body after 18 hours if 12.0 grams was injected?
18/6 = 3 half lives = 1/(2^3) = 1/8
12 x (1/8) = 1.5 grams
Which Nuclear Energy Process produces the least amount of radioactive waste?
Describe differences in Fusion and Fission
Fusion = combining
Fission = splitting
Why irradiate food stuff?
What are ionic bonds?
A type of chemical bond formed through an electrostatic attraction between two oppositely charged ions. Ionic bonds are formed between a cation, which is usually a metal, and an anion, which is usually a nonmetal
*the attraction between positive and negative ions
What are the names and formulas for ionic compounds?
What are polyatomic ions?
Compounds formed from more than one element having an overall change
What are covalent bonds?
A bond where atoms share some or all of their valence electrons in such a manner as to achieve a noble gas configuration about each atom
What are the names of covalent compounds?
How do we predict the shape of molecules?
Determined from the number of bonding pairs and the number of ion pairs on the central atom
*use Lewis structures to determine shape
What are the properties on ionic and covalent bonds?
What are intermolecular forces?
In a molecular compound, the attractions between individual molecules
*include hydrogen bonding and dipole-dipole
What are the states of matter?
Solid, Liquid, Gaseous
What makes water unique?
The attractive forces between positive and negative ions in a crystal lattice are called ______ bonds.
Positive ions are formed from neutral atoms by:
a)losing elections
b)gaining electrons
What change is expected when the following atoms form ions?:
a)Lithium (L)
b)Aluminum (Al)
c)Sulfur (S)
d)Bromine (Br)
Which of the following atoms form positive ions?:
a)Potassium (K)
b)Bromine (Br)
c)Nitrogen (N)
d)Sodium (Na)
Negative ions are formed from neutral atoms by:
a)losing electrons
b)gaining electrons
The name of SO2 is _____
The formula for sulfur trioxide is _____
The name of HBr is ______
The formula of dichlorine monoxide is _____
The formula for sulfur dichloride is _____
The name of SiCl4 is ______
How many electrons are shared in:
Which is the strongest bond?:
An example of a molecule with covalent bonds in which the electrons are
a)equally shared between the atoms is _____.
b)unequally shared between the atoms is _____.
What is the geometry of CH4?
Which is a more polar molecule?:
a)H-H or H-F
b)C-H or C-O
c)H-N or C-N

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