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- 2. a substance that takes part in and undergoes change during a reaction.
- 5. column of the periodic table. They are extremely reactive.
- 7. A chemical formula is a way of expressing information about the proportions of atoms that constitute a particular chemical compound, using a single line of chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs.
- 9. A chemical equation is the symbolic representation of a chemical reaction in the form of symbols and formulas.
- 10. Chemical changes occur when a substance combines with another to form a new substance, called synthesis or, alternatively, decomposes into two or more different substances. These processes are called chemical reactions and, in general, are not reversible except by further chemical reactions.
- 11. the result of a chemical reaction.
- 12. The alkali metals are a group of elements in the periodic table. They are all in the
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- 1. The law of conservation of mass or principle of mass conservation states that for any system closed to all transfers of matter and energy, the mass of the system must remain constant over time, as system mass cannot change quantity if it is not added or removed. Hence, the quantity of mass is "conserved" over time.
- 3. A chemical bond is a lasting attraction between atoms that enables the formation of chemical compounds.
- 4. Physical changes occur when objects or substances undergo a change that changes the physical form of a composition but not the chemical composition.
- 6. An electron in an outer shell of an atom that can participate in forming chemical bonds with other atoms.
- 8. The noble gases make a group of chemical elements with similar properties. Under standard conditions, they are all odorless, colorless, monatomic gases with very low chemical reactivity. The six noble gases that occur naturally are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn).