Depicting ElectronsELECTRON-DOT NOTATION

Inner & Outer Electrons

• Atoms consist of inner and outer electrons.

• Only the outermost electrons in an atom can participate in bonding.• Called valence electrons.

• The inner electrons do not participate in bonding.• Called non-bonding electrons.

Determining Number of Valence Electrons

• Each group on the periodic table has a set number of valence electrons.• Group 1 elements have 1 valence electron.• Group 2 elements have 2 valence electrons.• Group 13 elements have 3 valence electrons.• Group 14 elements have 4 valence electrons.• Group 15 elements have 5 valence electrons.• Group 16 elements have 6 valence electrons.• Group 17 elements have 7 valence electrons.• Group 18 elements have 8 valence electrons.

Electron-Dot Notation

• Depiction of the valence electrons of an atom.• Valence electrons are represented as dots surrounding the

elemental symbol.

• Fill in the blank periodic table with electron-dot notations. USE PENCIL.

Ions

• Ions form when atoms gain or lose electrons.• Cations form when electrons are lost.• Positively charged.• Charge is determined by number of electrons lost.

• Anions form when electrons are gained.• Negatively charged.• Charge is determined by number of electrons gained.

• Octet rule: atoms will gain or lose electrons so that they have 8 valence electrons.

Predicting Ions

• Atoms with fewer than four valence electrons will lose electrons to form cations.• A group 1 atom will lose 1 electron to form a 1+ cation.• A group 2 atom will lose 2 electrons to form a 2+ cation.• A group 13 atom will lose 3 electrons to form a 3+ cation.

• Atoms with more than four valence electrons will gain electrons to form anions.• A group 15 atom will gain 3 electrons to form a 3- anion.• A group 16 atom will gain 2 electrons to form a 2- anion.• A group 17 atom will gain 1 electron to form a 1- anion.

Predicting Ions

• Certain groups do not form ions.• Group 14 (carbon group).• Group 18 (noble gases).

Electron-Dot Notation of Ions

• Cation formation:• Remove the number of electrons appropriate for the group.• Charge is positive and equal to the number of electrons lost.

• Anion formation:• Add the number of electrons appropriate for the group.• Charge is negative and equal to the number of electrons gained.

• Edit your periodic table to show ion formation by removing or adding electrons to the electron-dot notation. Be sure to indicate the charge of the ions.