U1Q1 Elements and Compounds

Front

What is an element?

Back

An element is a pure substance that cannot be broken down into simpler substances by chemical means. It consists of only one type of atom.

Front

What is a compound?

Back

A compound is a substance formed when two or more different elements are chemically bonded together. For example, water (H2O) is a compound made of hydrogen and oxygen.

Front

What is a molecule?

Back

A molecule is the smallest unit of a chemical compound that retains its chemical properties. It can consist of two or more atoms of the same or different elements.

Front

What is the difference between a chemical symbol and a chemical formula?

Back

A chemical symbol represents a single element (e.g., O for oxygen), while a chemical formula represents a compound and shows the elements and their ratios (e.g., H2O for water).

Front

Give an example of a molecule made of two atoms of the same element.

Back

O2 (oxygen gas) is a molecule made of two oxygen atoms.

Front

Give an example of a compound.

Back

CO2 (carbon dioxide) is a compound made of one carbon atom and two oxygen atoms.

Front

What does the chemical formula NaH represent?

Back

NaH represents sodium hydride, a compound made of sodium and hydrogen.

Front

What does the chemical symbol Cl represent?

Back

Cl represents chlorine, which is an element.

Front

What is the chemical formula for water?

Back

The chemical formula for water is H2O.

Front

What is the chemical formula for table salt?

Back

The chemical formula for table salt is NaCl.