Valence Electrons Ions

1.  What is a valence electron?

2.  Draw the Bohr diagrams for the following elements.

Na Cl Ne Ca

3.  How many valence electrons does each element have?

§  Sodium=

§  Chlorine=

§  Neon=

§  Calcium=

The number of valence electrons can be determined by the elements placement on the periodic table. For Example, group 1 has 1 valence electron. Groups 3-12 vary in the number of valence electrons.

4.  Write the number of protons and electrons for each element. Color in the valence electrons for each element.

Na Cl Ne

# p+ = # p+ = # p+ =

#e- = #e- = #e- =

An atom achieves stability when it has a full valance shell. For most atoms this is achieved by following the OCTET rule. The octet rule states that an atom will have a full valence shell with eight valence electrons. This allows the atom to be stable. There are a few exceptions to this rule. Hydrogen and Helium follow the DUET rule. The duet rule states that an atom will have a full valence shell with two valence electrons. This allows the atoms to be stable. ALL noble gases have a full valence shell.

5. 

Element
symbol / Element Name / Electrons / Valence Electrons / How many more valence electrons would it need to gain to reach stability?
He
H
Al
O
F
S
Sr
Li
Br
Ba
Ar
Mg
P

Lewis dot diagrams are a way to show the number of valence electrons of an atom. Lewis dot diagrams place the valence electrons around the element symbol. Two electrons to each side for a total of eight. When you place the valence electrons you always place one on each side before you begin to place two on a side. Exceptions:

6.  Draw the Lewis Dot Diagrams for each of the following elements.

§  Fluorine

§  Hydrogen (Duet Rule)

§  Oxygen

§  Calcium

§  Lithium

§  Sodium

§  Sulfur

§  Chlorine

§  Neon

An ion is a Charged particle. This occurs when the number of electrons(-) do not equal the number of protons(+). If the number of protons is greater than the number of electrons than the ion will have a positive charge. This is called a cation because it is positive. If the number of protons is less than the number of electrons than the ion will be negative. This is called an anion because it is negative. Atoms become charged by gaining or losing electrons. Atoms will gain or lose electrons to attain a full valence shell. If an atom loses its valence electrons it will revert to the previous shell which is full. If an atom gains valence electrons it will gain enough to fulfill the octet rule. If an atom has 3 or less valence electrons, it will lose the electrons. If an atom has 5 or more valence electrons it will gain electrons to equal eight valence electrons. An atom with 4 valence electrons can gain or lose electrons. Usually it will lose the four valence electrons.

7.  Complete the table.

Element / Valence Electrons / # of Electrons Gained / # of Electrons Lost / # of Protons
(+) / # of Total Electrons
(-) / Overall Charge / Cation
or
Anion
Calcium
Chlorine
Bromine
Sodium
Hydrogen
Sulfur
Oxygen
Aluminum
Phosphorus
Potassium
Nitrogen
Selenium
Strontium
Iodine

8.  Write the ionic symbol for each of the elements in the table from #7.

Transition Elements will use roman numerals in their name to signify the charge of the ion. For example, Iron (III) is an ion that has a charge of positive three (Fe3+). You need to know roman numerals one to ten.

9.  Complete the following table.

Element / Ionic Symbol / Metal or Nonmetal / Anion or Cation
Calcium
Bromine
Nitrogen
Iron (II)
Cobalt (III)
Tin (II)
Fluorine
Cesium
Copper (I)
Copper (II)
Aluminum
Manganese (IV)
Magnesium
Lead (IV)

Naming Ions

An anion is named by dropping the end of the element name and adding an –ide ending. Then add the word ion. Example: Cl- This is the chloride ion. A cation is named by using the element name and adding the word ion to it. Example: Ca2+ This is the calcium ion. Ions with variable charges are named by using the element name, roman numerals to signify the charge, and then the word ion. Example: Hg2+ This is mercury (II) ion.

10.  Write the names of the following ions.

Ion / Name / Ion / Name
H+ / Pb2+
K+ / N3-
O2- / Ba2+
Sn2+ / F-
S2- / Pb4+