Electron Configuration Shorthand electron configuration

Using shorthand electron configuration Na 1s2 2s2 2p6 3s1 Ca 1s2 2s2 2p6 3s2 3p6 4s2 Shortcut of electron configuration using noble gases [Ne] 3s1 [Ar] 4s2 Normal electron configuration Shorthand electron configuration

Ions

What are Ions? Atoms can gain or lose electrons. If an atom gains or loses electrons, it will obtain a charge Ions are charged atoms.

Types of Ions: Cations and Anions If Na lost an electron what is its charge? If Ca lost 2 electrons what is its charge? Atoms with a positive charge Atoms that have lost electrons Na+ Ca 2+

Types of Ions: Cations and Anions If S gains two electrons, what is its charge Atoms with a negative charge Atoms that have gained electrons S2-

Valence Electrons

What is a valence electron? Valence electrons are the electrons in the highest occupied energy level of an element’s atoms. Cl = 1s2 2s2 2p6 3s2 3p5 Cl has 7 electrons in its last energy shell. Number of valence electrons largely determines the chemical properties of an element.

What is a valence electron? Valence electrons are also related to the group numbers of the periodic table. 1A --- 1 valence electron 2A --- 2 valence electrons 3A --- 3 valence electrons 4A --- 4 valence electrons 5A --- 5 valence electrons 6A --- 6 valence electrons 7A --- 7 valence electrons 8A --- 8 valence electrons Helium is the exception It has 2 valence electrons

Ca : Valence electrons What is the electron dot structure of S ? Valence electrons are usually the only electrons used in chemical bonds. Valence electrons are usually shown in electron dot structures. Example: Ca Ca : .. : S :

Electron Configuration in Chemical Bonding The Octet Rule In forming compounds, atoms tend to achieve the electron configuration of a noble gas. Octet = a set of eight ns2 np6

Electron configurations for Cations Cations are atoms with a positive charge Metals tend to become cations. Metals tend to lose their valence electrons, leaving a complete octet in the next-lowest energy level. What is a Cation? Metals

Electron Configurations for Anions Nonmetals Nonmetals tend to gain electrons since they have their last energy level almost full, it is easier to gain electrons than to lose them. Nonmetals tend to form anions Anions are atoms with a negative charge