Ionic Bonding (Part I) One Atom’s Loss (of an Electron) is Another Atom’s Gain

Chemical Bonds The forces that hold groups of atoms together and make them function as a unit. Ionic Bonds: the transfer of electrons Covalent Bonds: the sharing of electrons

Chemical Bonding Characteristics Ionic –Metal with Non-metal –Transfer of electron(s) –Strong bond…high melting point Covalent –Non-metal with Non-metal –Sharing of electron(s) Non-polar (equal distribution of electrons) Polar (uneven electron distribution) –Weak bonds…low melting points Single, double and triple bonds

Bonding Uses Valence Electrons Valence electrons are the electrons in the atom’s highest numbered energy level. They are the ones left over after the noble gas shorthand: the Lewis Dot Diagram dots!

Simple Way to Figure Lewis Dots (Before I made you do all that hard work with electron configuration and then noble gas shorthand.) Find the element’s group. Group 1A elements get 1 Lewis dot. Group 2A elements get 2 Lewis dots. Group 3A elements get 3 Lewis dots. Group 4A elements get 4 Lewis dots. Group 5A elements get 5 Lewis dots. Group 6A elements get 6 Lewis dots. Group 7A elements get 7 Lewis dots. Group 8A elements get 8 Lewis dots.

Octet Rule In forming compounds, atoms gain, lose, or share one or more valence electrons in such a way that they achieve the electron configuration of the nearest noble gas in the periodic table. This means that an ion will have either 0 or 8 Lewis dots.

Ionic Bonding  Atoms lose or gain electrons to form ions  Cations are positive ions  metals generally form cations  Anions are negative ions  non-metals generally form anions  Ionic compounds are held together by electrostatics—the positive charge of the cation attracting the negative charge of the anion.

Formation of a Cation 11p + sodium atom Na e-e- loss of one valence electron e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- sodium ion Na + 11p + e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- The same EC as Neon e-e-

Formation of a Cation Using Lewis Dot Diagrams Sodium atom loss of one valence electron Sodium ion Na + Na

Formation of Anion 17p + e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- gain of one valence electron 17p + e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- chlorine atom Cl chloride ion Cl - The same EC as Argon e-e-

Formation of an Anion Using Lewis Dot Diagrams Chlorine atom loss of one valence electron Chloride ion Cl - Cl

Formation of Ionic Bond 11p + e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- 17p + e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- sodium ion Na + chloride ion Cl -

Formation of an Ionic Bond Using Lewis Dot Diagrams NaCl + - NaCl

Ionic Bonding: Two Examples

Ionic Compound  METAL + NONMETAL  Important metal ions  group 1A - lose 1 electron (+1)  group 2A - lose 2 electrons (+2)  group 3A - lose 3 electrons (+3)  Important non-metal ions  group 7A (-1), group 6A (-2), group 5A (-3)  Transition metals also form ionic compounds  Their behavior is less predictable  Iron forms Fe +2 or Fe +3 ; Copper forms Cu + or Cu +2

The Formation of Ions Means That Negatively Charged Electrons are Transferred (Protons Stay Put in the Nucleus) Subtracting a negative charge from an atom makes the resulting ion positive. Adding a negative charge to an atom makes the resulting ion negative. Multiple subtractions or additions of negative charges results in multiply charged positive ions and multiply charged negative ions, respectively.

In Atomic Structure, Protons and Electrons Were Equal in Number For ions, protons and electrons cannot be equal in number. In the case of positive ions (cations), for each unit of positive charge, there will be one less electron than the number of protons in the nucleus. In the case of negative ions (anions), for each unit of negative charge, there will be one more electron than the number of protons in the nucleus.