Valence Electrons & Group Properties

5.3

Valence ElectronsElements in a group have similar properties

because they have the same number of valence electrons.

A valence electron is an electron that is in the highest occupied energy level of an atom.

Valence Electrons & Group NumberWhen the A groups in the periodic table are numbered from 1 through 8, the group number matches the number of valence electrons in the electron configuration of an element in that group.

• Valence electrons play a key role in chemical reactions.

• Properties vary across a period because the number of valence electrons increases from left to right.

Alkali MetalsGroup 1A1 Valence ElectronExtremely Reactive and thus found only in

nature as compounds

Alkaline Earth MetalsGroup 2A2 Valence ElectronsHighly Reactive

Spinach plant

Oyster shell with pearl

Plaster cast

Boron FamilyGroup 3A3 Valence ElectronsEx: Aluminum =

Most abundant metal in Earth’s Crust

Lab Glass materials

Carbon FamilyGroup 4A4 Valence Electrons

Nitrogen FamilyGroup 5A5 Valence ElectronsElements with a wide range of physical

propertiesUsed a lot in fertilizer

Oxygen FamilyGroup 6A6 Valence

ElectronsEx: Oxygen is the

most abundant element in the Earth’s crust

HalogensGroup 7A7 Valence ElectronsFound as gas, liquid or

solidDespite these differences,

chemical properties are the same

Noble GasesHe has 2 valence electronsAll the others have 8Colorless, odorless and extremely unreactive

= STABLE

Noble GasesBut, when electric

current passes through noble gases, they emit different colors. Helium emits pink, neon emits orange-red, argon emits lavender, krypton emits white, and xenon emits blue.

Electron Dot DiagramWhen is an atom unlikely to react?When the highest occupied energy level of an atom is filled with electrons, the atom is stable and not likely to react.

Electron Dot DiagramThe chemical properties of an

element depend on the number of valence electrons. An electron dot diagram is a model of an atom in which each dot represents a valence electron. The symbol in the center represents the nucleus and all the other electrons in the atom.

Electron Dot Diagram

Electron Dot Diagram

Electron Dot Diagram

Electron Dot Diagram

Electron Dot Diagram

Electron Dot Diagram

Electron Dot Diagram

Electron Dot Diagram

Electron Dot Diagram