Forming ions Atoms form ions An atom has

Atoms form ions An atom has an equal number of electrons and protons. Ø

Formation of positive ions Ø If an atom loses one or more electrons, the

Formation of negative ions Ø If an atom gains one or more electrons, the

Example of Positive Ion Ø Sodium atom (Na) • 11 protons • 11 electrons

Example of Negative Ion Ø Chlorine atom (Cl) 17 protons • 17 electrons •

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Forming ions

Atoms form ions An atom has an equal number of electrons and protons. Ø Since each electron has a negative charge, and each proton has a positive charge, atoms have no overall charge. Ø An ion is formed when an atom loses or gains one or more electrons. Ø Because the number of electrons in an ion is different from the number of protons, an ion DOES have an overall electric charge. Ø

Formation of positive ions Ø If an atom loses one or more electrons, the charges are no longer balanced. Ø If there are more protons than electrons, then the ion formed is positive. Ø The size of the positive ion is smaller than the atom that formed it due to less electrons – less of a repulsion among the remaining electrons.

Formation of negative ions Ø If an atom gains one or more electrons, the charges are no longer balanced. Ø If there are less protons than electrons, then the ion formed is negative. Ø The size of the negative ion is larger than the atom that formed it due to more electrons causing repulsion and expansion.

Example of Positive Ion Ø Sodium atom (Na) • 11 protons • 11 electrons When sodium loses an electron, it becomes a positive ion because it now has 11 protons and only 10 electrons.

Example of Negative Ion Ø Chlorine atom (Cl) 17 protons • 17 electrons • When chlorine gains an electron, it becomes a negative ion because it now has 17 protons and 18 electrons.