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Explore how atoms transfer electrons to form charged ions and create strong attractions.
Why does ordinary table salt form perfect little cubes instead of random blobs? The secret lies in a microscopic 'tug-of-war' where one atom completely gives up and hands over its prize.
Most atoms are 'unhappy' because their outer electron shells are not full. According to the Octet Rule, atoms are most stable when they have 8 valence electrons. Metals (like Sodium) usually have 1, 2, or 3 valence electrons, while nonmetals (like Chlorine) have 5, 6, or 7. Instead of sharing, these atoms engage in electron transfer. The metal atom 'donates' its extra electrons to the nonmetal. This isn't just a friendly gift; it's a move toward total stability. Once the transfer happens, both atoms achieve a full outer shell, similar to a Noble Gas.
Quick Check
Why do metals tend to lose electrons rather than gain them to reach a full octet?
Answer
Metals usually have only 1-3 valence electrons; it requires much less energy to lose those few electrons than to find and pull in 5-7 more.
When an atom loses or gains an electron, it is no longer neutral; it becomes an ion. Because electrons have a negative charge, losing one makes the atom positive. We call a positive ion a cation (think of the 't' in cation as a plus sign , or remember that 'cats' are 'paws-itive'). Conversely, when a nonmetal gains an electron, it becomes a negative ion, known as an anion. The magnitude of the charge depends on how many electrons moved. For example, losing two electrons creates a charge.
1. A Sodium () atom has 1 valence electron. 2. A Chlorine () atom has 7 valence electrons. 3. transfers its 1 electron to . 4. becomes (a cation). 5. becomes (an anion). 6. Both now have stable outer shells.
Quick Check
If a Magnesium atom loses 2 electrons, what is its new chemical symbol and charge?
Answer
Now that we have a positive cation and a negative anion, something magical happens: electrostatic attraction. Just like the opposite poles of magnets, the positive and negative charges pull toward each other with immense force. This attraction is the ionic bond. These ions don't just pair up in isolated couples; they stack together in a repeating 3D pattern called a crystal lattice. This rigid structure is why ionic compounds, like salt, are hard, brittle, and have very high melting points.
Consider Magnesium () and Fluorine (). 1. wants to lose 2 electrons to become . 2. only needs 1 electron to become . 3. To balance the charges, one atom must give electrons to two different atoms. 4. The resulting formula is , where the total positive charge () equals the total negative charge ().
How do Aluminum (, 3 valence electrons) and Oxygen (, 6 valence electrons) bond? 1. wants to lose 3 (). 2. wants to gain 2 (). 3. To find the lowest common multiple of 2 and 3, we need 6 electrons transferred. 4. Two atoms () bond with three atoms (). 5. The final stable compound is .
Which of the following best describes an ionic bond?
If an atom gains 3 electrons, what is its charge?
Ionic compounds usually form a repeating 3D structure called a crystal lattice.
Review Tomorrow
In 24 hours, try to explain to a friend why a ion and a ion stay stuck together without using the word 'glue'.
Practice Activity
Look at a periodic table and try to predict the ionic formula for Calcium () and Chlorine ().