U1 7.6ab elements & compounds, atoms, chemical formulas

Front

What is an element?

Back

An element is a pure substance that cannot be broken down into simpler substances by chemical means. Each element is made up of atoms that have the same number of protons.

Front

What is a compound?

Back

A compound is a substance formed when two or more elements chemically bond together in fixed proportions. For example, carbon dioxide (CO2) is a compound made of carbon and oxygen.

Front

What is the atomic number?

Back

The atomic number is the number of protons in the nucleus of an atom, which determines the element's identity.

Front

What is a chemical formula?

Back

A chemical formula is a way of representing a chemical substance using symbols for its constituent elements and numbers to indicate the ratio of atoms.

Front

How many atoms are in a molecule of water (H2O)?

Back

A molecule of water (H2O) contains 3 atoms: 2 hydrogen (H) atoms and 1 oxygen (O) atom.

Front

What does the subscript in a chemical formula indicate?

Back

The subscript in a chemical formula indicates the number of atoms of the element that are present in the molecule. For example, in H2O, the '2' indicates there are 2 hydrogen atoms.

Front

What is the difference between an atom and a molecule?

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An atom is the smallest unit of an element, while a molecule is a group of two or more atoms bonded together.

Front

What is the symbol for zinc and its atomic number?

Back

The symbol for zinc is Zn, and its atomic number is 30.

Front

How many oxygen atoms are in sulfuric acid (H2SO4)?

Back

There are 4 oxygen atoms in sulfuric acid (H2SO4).

Front

How many carbon atoms are in the chemical formula C2(H4O2)3?

Back

There are 2 carbon atoms in the chemical formula C2(H4O2)3.