Elements and Compounds - Unit 3 - Review Sheet

What is a compound?

A compound is when two or more elements combine chemically

How does a group differ from a period on the periodic table? How many groups are there? How many periods?

A group is a column on the periodic table( up and down), there are 18. A period is a row on the periodic table (left to right), there are 7

Element

An element is a pure substance that cannot be separated into simpler substances.

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

Compounds are put together and separated chemically(electrolysis, heat). You cannot pick apart a compound or filter out the parts.

Why is an element considered a pure substance?

It is considered "pure" because it cannot be broken down into any other ingredients.

Calculate the amount of atoms of each element within the compound

Li2O Li-2 O-1 2 NaOH Na-2 O-2 H-2 Li2(SO4)2 Li-2 S-2 O-8 Al(OH)3 Al-1 O-3 H-3

What are the three categories of elements?

Metals, Nonmetals, Metalloids.

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

When elements combine to form a compound they go through a chemical change. Sp the properties that make up the original elements are different than the properties of the compound they make.

Can a compound be considered a pure substance?

Yes because a compound is ONLY made up of particle of itself. Water is made of water molecules.

Nonmetals

dull, brittle, nonmalleable, non ductile, gas, poor conductors

Metaloids

shares characteristics of both metals and nonmetals, semiconductors

Metals

shiny, malleable, ductile, good conductor, solid