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Last update: July 20, 2015

 
Chm-2
 
 
Groups of Positive and Negative Ions in the Periodic Table
 
 
Posted: May 28th, 2015
 

One of the most important ways the periodic table is ordered is by groups which refer to the columns of the table. The groups are significant because they often relate to what kind of charge the atom has, for example group 1 has a positive charge of 1, group 2 has a positive charge of 2 and group 3 has a positive charge of 3. Going backwards from the right side of the table, skip over group 8 the noble gases because they do not gain or lose electrons, and group 7 has a negative charge of 1, and group 6 has a negative charge of 2. See pdf of charges of monatomic ions

Briefly summarizing, the columns on the left side of the periodic table and the middle section are the metals, which form positive ions. Positive ions are formed because the atoms of the elements lose electrons. The flat horizontal middle section of the table are called the transition metals which also form positive ions. Positive ions are called cations pronounced (Cat-Eye-On's). The negative ions are located in the columns on the right side of the table. There is a stair step section between the transition metals and the non-metals called metalloids. Negative ions are called anions.

A connection between chemistry and math exists in the fact that the equation for an ionic compound must have a net charge of zero. That means that every ionic compound (molecule made of two or more types of atoms) will have at least one positive ion and one negative ion so that they can balance the charge of the total ion and make it equal to zero.

To understand how to write chemical formulas for ionic compounds you must know how to identify the ionic charge of each individual atom. The ionic charge is the superscript which does not appear in the final chemical formula, however it is necessary to know the ionic charge of each individual atom to determine the formula. For many of the elements, this bit of information, the value of its charge, is based on what group (column) the element is located in on the periodic table.

As already described in paragraph 1, if an element is in group 1 such as Hydrogen, Lithium, Sodium, Potassium, Rubidium, Cessium and Francium, it has a positive charge of 1 because it loses one electron and gains 1 proton. In chemistry electrons are considered negatively charged and protons are considered positively charged . Thus an element which forms an ion by losing an electron and gaining a proton is said to have a positive charge.

If the element is in Group 2, like Beryllium, Magnesium, Calcium, Strontium, Barium, and Radium, then it loses 2 electrons and gains 2 protons, giving it a positive charge of 2. These are the group 2 metals.

Group 3 works the same way, its elements are metals and they have a positive charge of 3 because they lose 3 electrons and gain 3 protons. In between group 2 and 3 on the periodic table are the transition metals. Although they are metals- which means they form cations - positive ions- their charge is not easy to predict like the groups 1 through 3 metals. There is no easy way to know what their charge is.

Charges of monatomic ions - pdf from www.gpb.org


By Andrea Boggs

 

 

 

Periodic Table

 

 

Reference list

Zumdahl, Steven S. (2004) Introductory Chemistry: A Foundation. Houghton Mifflin Company: Boston, New York.

  • p.109 "Transition metals form cations with various charges."
  • p.109 "Thus for groups 1 through 3 the charges of the cations formed are identical to the group number."

 





 

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