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4th Qtr Test

4th Quarter review test for 8th Grade Science (Chemistry)

The breakdown of a nucleus when the strong force is not large enough to overcome repulsion of positive (+) charges in protons Radioactivity
Atoms of the same elements that have different masses (different numbers of neutrons) like C-12 and C-14 Isotope
What do we use to determine whether an atom is stable? The proton/neutron ratio (p/n)
What ratios are considered stable? 1 for small atoms (top rows); .67 for large atoms (bottom rows)
How would you determine the number of neutrons in Radium 222? Subtract the atomic number (protons) from the mass number: 222 – 88 = 134 neutrons
What type of radiation emits a Helium nucleus (2 protons/2 neutrons) and is stopped by paper? Alpha
What type of radiation emits an electron (negative) and is stopped by a thin foil of metal Beta
This is a penetrating electromagnetic radiation, stopped only by thick concrete or lead Gamma
In finding how much of a sample of an isotope is left after x half-lifes, what must you do? Repeatedly divide by 2 (100/2 => 50/2=>25 – 2 half-lives)
The splitting of a large nucleus is called Fission
The combining of 2 smaller nuclei to make a large nucleus is called fusion
The Sun is an example of what type of nuclear reaction? Fusion (H atoms fuse to create He)
What type of nuclear reaction are power plants an example of? Fission (splitting nuclei and creating radioactive waste)
What tells how many atoms of an element are in a molecule? Subscripts (small numbers found after the symbols)
What tells how many molecules of a compound are in a reaction? Coefficient (Large number found before groups of symbols – multiplies all elements in the molecule)
Why do atoms form chemical bonds? Atoms need to have a full outer energy level to be stable. This is eight (8) electrons for most elements, two (2) for H and He.
Which type of bonding occurs between a metal and a nonmetal? Ionic
Which type of bonding occurs between two nonmetals covalent
Which type of bonding occurs when elements gain or lose electrons? Ionic
Which type of bonding occurs when metals give up their electrons and share them? metallic
Which type of bonding occurs when elements share electrons? Covalent
What are the steps in Ionic Naming? 1. Write the name of the first element 2. Write the name of the second element, ending with “ide” or the polyatomic ion 3. Check oxidation numbers (if there is more than one, balance charges to determine which one)
What are the steps in Covalent Naming? 1. Write the first element with a prefix that indicates how many of that element are in the compound (no mono-) 2. Write the second element with a prefix (including mono-), and ending in “ide.”
What must you check in naming ionic compounds? You must balance the charges
Why do some compounds include Roman numerals (ex: Copper (I) Oxide)? Some metals have multiple oxidation numbers. The numeral is determined by balancing charges.
In what type of reaction do two or more substances combine to form one new compound? Synthesis
In what type of reaction does one substance break down into two or more substances? Decomposition
When an element reacts with a compound to produce a new compound and a different element, that is a ______ reaction single displacement
When two compounds react to form two DIFFERENT compounds, that is a ______ reaction double displacement.
How can you tell when equations balance? Both sides of the equation have the same number of each element.
Created by: judi829