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Homework Help: How are ions formed from atoms?

  1. Sep 2, 2008 #1
    1. How are ions formed from atoms?

    Attempt at Solution: From reading books and browsing on the internet I've collected a good amount of information, but I don't completely understand them.

    "An ion is formed when an atom gains or loses an electron in bonding with another atom, causing the atom to become a positive or negative ion. Since electrons are negative, if an atom loses an electron, there are more protons (which are positive) than electrons, which causes the atom to become a positive ion (sometimes called a cation.) If an atom gains an electron it becomes a negative ion (or anion.) Ions are most commonly formed when two elements undergo ionic bonding, in which the elements 'give and take' electrons to gain full outer shells."

    Can someone interpret that into a simpler format or give an example of an equation to demonstrate.

  2. jcsd
  3. Sep 2, 2008 #2


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    when Na loses an electron,e, it becomes Na+

    Eq'n: Na - e-->Na+
  4. Sep 2, 2008 #3
    So Na has 11 protons and 11 electrons. If my teacher gave me a problem like,

    Cl-, then the answer would be 17 protons and 18 electrons right cause you add one more?
    So I have to know the charges of the groups of the periodic table to figure it out right?
  5. Sep 3, 2008 #4


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    Well you usually you are given a periodic table. But you should learn how the table is put together, for example, all the elements in group 7, in ionic form have a -1 charge [halid ions].
  6. Sep 3, 2008 #5


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    The basic principle is that most (but not all) atoms will strive to have the same number of electrons as the nearest noble gas. Chlorine gains one electron to become the negatively charged chloride ion because gaining an electron gives it the same number of electrons as argon.

    Having the same number of electrons as a noble gas (or more importantly, the same electron configuration) makes the atom much more stable.
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