Name:
Introduction to Ions Activity
Using the ion puzzle pieces, complete the following compounds.
1.
Na + Br
Charge of Na:
Picture:
How many Na:
Formula:
2. K + S
Charge of K:
Picture:
How many K:
Formula:
3. Ga + Cl
Charge of Ga:
Picture:
How many Ga:
Formula:
4. Cs + O
Charge of Cs:
Picture:
How many Cs:
Formula:
5. Ca + N
Charge of Ca:
Picture:
How many Ca:
Formula:
Charge of Br:
How many Br:
Charge of S:
How many S:
Charge of Cl:
How many Cl:
Charge of O:
How many O:
Charge of N:
How many N:
Ionic Bonding and Chemical Formulas
When a chemical formula for a compound is written correctly, it shows the number of each type
of atom in the compound. These numbers, called subscripts, are determined by the bonding between
atoms.
The table shows two columns of elements. The element in the first column usually give up
electrons when they form compounds. The elements in the second column usually gain electrons when
they form compounds. The column next to the elements gives the number of electrons found in the
outer level of each element. Using this information, determine the charge on the ion after the exchange
of electrons. Remember, atoms that give up electrons become positive ions (called cations), while
elements that gain electrons become negative ions.
Now, show how the positive ion would combine with the negative ion to make a neutral
compound. For example, Sodium (Na) has one electron in its outer level. It gives up this electron and
becomes a 1+ ion. Sulfur (S) having six electrons in its outer level gains two electrons to fill this outer
level with eight electrons. Sulfur becomes a 2- ion. These two ions then combine to form Na2S. This
formula is correct because it takes two sodium ions to match the 2- charge on one sulfur ion.
Element
Sodium
Valence
Electrons
1
Charge on
the Ion
+1
Element
Sulfur
Magnesium
Bromine
Sodium
Oxygen
Lithium
Oxygen
Calcium
Phosphorus
Barium
Chlorine
Beryllium
Sulfur
Strontium
Fluorine
Sodium
Astatine
Aluminum
Oxygen
Valence
Electrons
6
Charge on
the Ion
2-
Formula
Na2S
Answer the following questions in complete sentences.
1. Consider the formula Na2S in the above example. It tells us that two Na+ ions are bonded to
one S2- ion. What is the overall charge for Na2S? Is it positive, negative, or neutral?
2. Consider MgBr2. This formula tells us that one Mg2+ ion bonds with two Br- ions. What is the
overall charge on MgBr2?
3. What is the overall charge on any ionic compound? Why?
4. Why is calcium nitride written like Ca3N2 and not something like CaN2 or Ca2N3? In other words,
why do exactly three calcium ions bond with exactly two nitride ions?