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8.2 Ionic Bonding

Ionic bonds occur between metal and non-metal atoms, where electrons are transferred from the metal atom to the non-metal atom. This creates positive ions (cations) and negative ions (anions), which attract each other due to their opposite charges. Examples of ionic compounds are sodium chloride (NaCl) and calcium oxide (CaO).

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8.2 Ionic Bonding

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  1. 8.2 Ionic Bonding

  2. Ionic Bonds • Ionic bonds are made between metaland non-metal atoms • Electrons are transferred from the metal atom to the non-metal atom • Metal atoms lose electrons form positive ions called cations. • Non metal atoms gain electrons form negative ions called anions.

  3. Metals • Metals atoms lose electrons to form positive ions (an atom that loses or gains electrons) called cations. E.g., Beryllium (Be) Group 2 Neutral atom Positive ion 4+ P’s 4+ P’s 4- E’s2- E’s 0 2+ Valence Electrons The electrons in the outer shell of an atom, which determines its power to combine with other elements

  4. Non-metals • Non-metal atoms gain electrons to form negative ions called anions. E.g., Carbon (Ca) Group 14 Neutral atom Negative ion 6+ P’s 6+ P’s 6- E’s 10- E’s 0 4-

  5. Let us consider the bonding in the substance sodium chloride. Na+ + Cl-Na+Cl- In this reaction the sodium (Na) atom loses 1 electron while the chlorine atom accepts the electron in the transfer process. An example of ionic bonding…..

  6. NaCl • Thus we can say that sodium chloride is an ionic compound

  7. Na+ Sodium ion This charged atom contains: 11+ Protons + 10- Electrons - 1 Cl- Chloride ion This charged atom contains: 17+ Protons + 18- Electrons +1 NaCl

  8. Sodium Chloride • Thus NaCl • Once these two ions (An atom that has become charged be gaining or losing one or more electrons) have been formed, they will attract each other because of their opposite charges

  9. CaO • Ca2+ + O2- Ca2+O2- • In this reaction the calcium (Ca) atom loses 2 electrons while the oxygen (O) atom accepts the two electrons in the transfer process.

  10. Thus we can say that calcium oxide is an ionic compound

  11. Calcium Oxide Ca2+ Calcium ion O2- Oxide ion 20+ Protons 8+ Protons 18- Electrons10- Electrons 2+ 2- Once these two ions have been formed, they will attract each other because of their opposite charges. There is an electrostatic attractive force present (like charges repel and unlike charges attract) that creates the chemical bond in the NaCl and CaO,called an ionic bond.

  12. Let’s try one….. Magnesium and Fluorine Metal Non-metal 12+ Protons 9+ Protons 10- Electrons10- Electrons 2+ 1- Mg2+ + F1- Mg2+F1- Chemical name: Magnesium fluoride Chemical Formula: MgF2

  13. Group 1 elements form cations with one positive charge. • Group 2 elements form cations with two positive charges. • Group 3 elements form cations with three positive charges. • Group 17 elements form anions with one negative charge. • Group 16 elements form anions with two negative charges. • group 15 elements form anions with three negative charges. Group number on the periodic table indicates the number of electrons the atom will lose or gain.

  14. Figuring out Ionic Charge • For metals, it‘s the same as thegroup number (the column number). • For non metals, the charge is equal to whatever number needs to be addedto the group number to get 8. Group 8, (the noble gases), don‘t form ions asthey do not need to gain any electrons to have a full outer shell

  15. More to try…….. Potassium and Sulfur Aluminium and Chlorine Aluminum and Oxygen Calcium and Fluorine

  16. Bonding in Ionic Compounds • According to the ionic electrostatic model, solids such as NaCl consist of positive and negative ions arranged in a crystal lattice. • Each ion is attracted to neighbouring ions of opposite charge, and is repelled by ions of like charge; this combination of attractions and repulsions, acting in all directions, causes the ion to be tightly fixed in its own location in the crystal lattice. Sodium metal reacts with chlorine gas in a violently exothermic reaction to produce NaCl (composed of Na+ and Cl- ions): 2Na(s) + Cl2(g) -> 2NaCl(s)

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