Unit 2 Test Review

Which is an example of a new substance being formed during a chemical change?

• glass breaking
• metal melting
• water freezing
• wood burning

Students combined baking soda and vinegar to demonstrate a chemical reaction. What indicates that a chemical reaction has occurred?

• the formation of bubbles
• a reduction in total mass
• the disappearance of atoms
• an increase in the number of atoms

______________- means written above (Ex: K+, I-)

• superscript
• subscript
• valence electron

_____________ ____________- when an element’s outer energy level is complete (8 electrons in outer level for most elements).

• stable energy
• chemical bond
• chemically stable

______________- the number written after a symbol that tells how many atoms of that element are in a unit of the compound.

• superscript
• subscript
• coefficient

The ____ tells you how many electrons an atom must gain, lose, or share to become stable.

• atomic mass
• atomic number
• ionic number
• oxidation number

If a symbol has no subscript, the number ________ is used.

• 1
• 2
• 0

A nitrogen and nitrogen bond contains 3 pairs of __________ electrons – triple bond.

• shared
• transferred

Which of the following statements best explains why atoms bond?

• Atoms bond to make new substances.
• Atoms bond to become less chemically stable.
• Atoms bond to change from a liquid to a solid.
• Atoms bond to be more chemically stable

Which of the following are most directly involved in chemical bonding?

• protons
• neutrons
• valence electrons
• quarks