SPM Form 4 Chemistry Notes — Chapter 5『5.2』Formation of Ionic Bonds

Formation of Positive Ions/Cations (Metals)

Atoms of elements in Group 1，2 and 13 with valence electron 1，2 and 3 will form POSITIVE ION （+，2+ and 3+）by donating electrons to attain a stable duplet/octet electron arrangement.

Na = 2.8.1 (proton no.和electron no.一样)

Na⁺ = 2.8 (因为捐了1 electron，是好人所以positively charge)

Mg = 2.8.2 (proton no.和electron no.一样)

Mg²⁺ = 2.8 (因为捐了2 electrons，所以2+)

Formation of Negative Ions / Anions (Non-Metals)

Atoms of elements in Group 15，16 and 17 with valence electron 5，6 and 7 will form NEGATIVE ION （-，2- and 3-）by receiving electrons to attain a stable duplet/octet electron arrangement.

O = 2.6 (还欠2 electrons)

O^2- = 2.8 (所以当从别的atom拿走2 electrons，就变negatively charge)

Cl = 2.8.7 (还欠1 electron)

Cl^- = 2.8.8 (因为从别的atom拿走1 electron)

Name for Atoms and Ions of Non-Metal Elements

Atoms	Ions
Oxygen, O	Oxide, O2-
Fluorine, Fl	Fluoride, Fl-
Chlorine, Cl	Chloride, Cl-
Bromine, Br	Bromide, Br-
Iodine, I	Iodide, I-

Positively charge的ions，名字的结尾是“ium”

Negatively charge的ions，名字的结尾是“ide”

至于要如何分辨Metals和Non-Metals，可以参考我的Periodic Table

Formation of Ionic Bonds

• Formed through the transfer of electrons between atoms of metal and non-metals. 『如果一个compound是由金属和非金属结合而成，那么一定会有转移electon』
• Metal atom donates an electron to form a positive ion (cation). 『好人捐东西，所以+』
• Electrons are transferred from metal atoms to non-metal atoms.
• Non-metal atom accepts electron to form a negative ion (anion). 『拿了别人的东西，所以-』
• The cation and anion are attracted to each other by strong electrostatic forces. 『正负互相吸引，这个吸引力称为electrostatic forces』
• The ionic bond is formed.

Formation of Sodium Chloride

• The electron arrangement of the sodium atom is 2.8.1.
• A sodium atom donates 1 electron to achieve the stable octet electron arrangement, 2.8.
• A sodium ion is formed. (Na → Na⁺ + ē)
• The electron arrangement of the chlorine atom is 2.8.7.
• A chlorine atom accepts 1 electron from the sodium atom to achieve the stable octet electron arrangement, 2.8.8.
• A chloride ion is formed. (Cl + ē → Cl^-)
• The sodium ion and chloride ion are attracted to each other by a strong electrostatic force.
• An ionic compound sodium chloride, NaCl is formed. (The strong electrostatic force between the oppositely-charge ions is called ionic bond or electrostatic bond)

Formation of Calcium Oxide

• The electron arrangement of the calcium atom is 2.8.8.2.
• A calcium atom donates 2 electrons to achieve the stable octet electron arrangement, 2.8.8.
• A calcium ion is formed. (Ca → Ca²⁺ + 2ē)
• The electron arrangement of the oxygen atom is 2.6.
• An oxygen atom accepts 2 electrons from the calcium atom to achieve the stable octet electron arrangement, 2.8.
• An oxide ion is formed. (O + 2ē → O^2-)
• The calcium ion and oxide ion are attracted to each other by a strong electrostatic force.
• An ionic compound calcium oxide, CaO is formed. 

Formation of Magnesium Fluoride

• The electron arrangement of the magnesium atom is 2.8.2.
• A magnesium atom donates 2 electrons to achieve the stable octet electron arrangement, 2.8.
• A magnesium ion is formed. (Mg → Mg²⁺ + 2ē)
• The electron arrangement of the fluorine atom is 2.7.
• A fluorine atom accepts 1 electron from the magnesium atom to achieve the stable octet electron arrangement, 2.8.
• A fluoride ion is formed. (Fl + ē → F^-)
• The magnesium ion and fluoride ion are attracted to each other by a strong electrostatic force.
• An ionic compound magnesium fluoride, MgF₂ is formed. 

Formation of Lithium Oxide

• The electron arrangement of the lithium atom is 2.1.
• A lithium atom donates 1 electron to achieve the stable duplet electron arrangement, 2.
• A lithium ion is formed. (Li → Li⁺ + ē)
• The electron arrangement of the oxygen atom is 2.6.
• An oxygen atom accepts 2 electrons from the lithium atom to achieve the stable octet electron arrangement, 2.8.
• An oxide ion is formed. (O + 2ē → O^2-)
• The lithium ion and oxide ion are attracted to each other by a strong electrostatic force.
• An ionic compound lithium oxide, Li₂O is formed.