Earth Science Chemistry Review I

1.  An atom has 7 protons, 7 electrons and 8 neutrons. Fill in the blanks for the following characteristics of this atom:

Atomic number: _____ Atomic mass: _____ Charge: _____

This atom belongs to which element? _______________________

How many shells or orbitals are present in the electron cloud? _____

2.  In the blanks below write the name of the element which corresponds to each of the following atomic numbers:

Atomic number 6: _____________________

Atomic number 10: _____________________

Atomic number 92: _____________________

Atomic number 26: _____________________

Atomic number 20: _____________________

Atomic number 4: _____________________

3.  An oxygen ion has a valence (electrical charge) of –2. How many protons and electrons does this ion have?

Protons: _____ Electrons: _____

4.  An ion of potassium (K) has a valence (electrical charge) of +1. How many protons and electrons does this ion have?

Protons: _____ Electrons: _____

5.  The mineral fluorite is composed of fluorine and calcium. Use the periodical table of the elements to determine what the valence of each of these elements will have when they combine to form a chemical compound (hint: determine how many electrons the element will have to gain or loose so that the outermost electron shell resembles the closest noble gas on the table).

Valence for fluorine (F): _____ Valence for calcium (Ca): ______

To form a compound, these elements must combine in a ratio which is electrically neutral (in other words the valence numbers must add up to zero). In the space below write the chemical formula for the compound which is formed into the mineral fluorite:

6.  In solid earth materials we can assume that the element oxygen will always have a valence of –2 (it will combine with 2 extra electrons to fill the outer electron shell or orbit). The chemical formula for the mineral quartz is SiO₂. What is the valence on the silicon (Si) in this compound?

Valence on Si: _____

7.  In some cases several atoms may bond to form a structure in which the electrical charge remains unbalanced. Such a structure is called a complex ion. One common complex ion is the carbonate ion, which consists of one carbon bonded with 3 oxygen atoms. Write the formula for the carbonate ion in the space below, and indicate the valence (net electrical charge) with a superscript in the upper right:

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