Elements and Compounds - Unit 3 Review

Why is an element considered a pure substance?

What are the three categories of elements?

What are the characteristics of metals?

What are the characteristics of nonmetals?

What are the characteristics of metalloids?

How does a group differ from a period on the periodic table?

Can a compound be considered a pure substance?

How are compounds put together and how are they broken down?

How do the properties of compounds compare to the elements that make them up?

Calculate the amount of atoms of each element within the compound Li2O. Li-, O-

Calculate the amount of atoms of each element within the compound 2 NaOH. Na-, O-, H-___

Calculate the amount of atoms of each element within the compound Li2(SO4)2. Li-, S-, O-___

Calculate the amount of atoms of each element within the compound Al(OH)3. Al-, O-, H-___

Elements

Elements are pure substances that cannot be separated into simpler substances.
An element is considered pure as it cannot be broken down into any other ingredients.

Categories of Elements

Elements are categorized into three groups:
- Metals: Shiny, malleable, ductile, solid, and good conductors of heat and electricity.
- Nonmetals: Dull, brittle, nonmalleable, non-ductile; can exist as gases and are generally poor conductors.
- Metalloids: Exhibit characteristics of both metals and nonmetals and function as semiconductors.

Periodic Table Structure

The periodic table consists of groups (columns) and periods (rows).
There are 18 groups and 7 periods on the periodic table.

Compounds

A compound forms when two or more elements combine chemically.
Compounds are pure substances made entirely of their own particles, such as water made of water molecules.

Formation and Breakdown of Compounds

Compounds are formed and separated through chemical processes, such as electrolysis or heat.
It is not possible to simply pick apart a compound; they cannot be filtered like mixtures.

Properties of Compounds vs. Elements

When elements combine to form a compound, they undergo a chemical change.
The resulting compound has different properties than the individual elements that compose it.

Atom Count in Compounds

For specific compounds:
- Li2O: Lithium (Li) - 2 atoms, Oxygen (O) - 1 atom
- 2 NaOH: Sodium (Na) - 2 atoms, Oxygen (O) - 2 atoms, Hydrogen (H) - 2 atoms
- Li2(SO4)2: Lithium (Li) - 2 atoms, Sulfur (S) - 2 atoms, Oxygen (O) - 8 atoms
- Al(OH)3: Aluminum (Al) - 1 atom, Oxygen (O) - 3 atoms, Hydrogen (H) - 3 atoms

Test your knowledge on elements and compounds with this Unit 3 review sheet flashcard quiz. Explore key concepts including the definition of an element, why it's considered a pure substance, and the categories of elements. Perfect for students studying chemistry.