Upload
others
View
3
Download
0
Embed Size (px)
Citation preview
Ions & Lewis Dot
Structures
Electrons
� Valence electrons – electrons in the highest occupied energy level of an element’s atoms
� Outermost energy level
� Only the electrons in the s & p orbitals
� Remember Bohr Diagrams?
Valence Electrons� Lithium: 1s22s1
� 2 electrons in 1st energy level
� 1 electron in 2nd energy level – Highest energy level
� 1 valence electron
� Fluorine: 1s22s22p5
� 2 electrons in 1st energy level
� 7 electrons in 2nd energy level
� 7 valence electrons
� Aluminum: 1s22s22p63s23p1
� 2 electrons in 1st energy level
� 8 electrons in 2nd energy level
� 3 electrons in 3rd energy level
� 3 valence electrons
Valence Electrons
�We can also use the group number as a shortcut to determine the number of valence electrons:
� Lithium: Group 1: 1 valence electron
� Fluorine: Group 17: 7 valence electrons
� Aluminum: Group 13: 3 valence electrons
� Valence electrons are the only electrons involved in creating chemical bonds.
� Lewis Dot Structures show just the valence electrons.
Lewis Dot Structures
� Element symbol is drawn with dots surrounding it representing valence electrons.
�Move clockwise around the atom adding a dot for each electron
Lewis Dot Structures
� All elements within a group have the same valence electrons, therefore the same electron dot structure.
Octet Rule
�Octet rule - When forming compounds all elements want to achieve the electron configuration of a noble gas.
�Everyone wants 8 electrons!!!! (except H, He, Li, Be and B - they only need 2)
�During reactions:
�Metal atoms tend to LOSE electrons
�Nonmetal atoms tend to GAIN electrons.
Cation
�When a metal loses an electron, it forms a cation.
� Cation - positively charged ion
� Na· � Na+ + e- Sodium Ion
� 11 protons (+)
� 10 electrons (-)
� · Mg· � Mg2+ + 2e- Magnesium Ion
� 12 protons (+)
� 10 electrons (-)
+1
+2
Anion
� When a nonmetal gains an electron, it forms an anion.
� Anion - negatively charged ion
� + e-�
� 17 protons (+)
� 18 electrons (-)
� + 2e- �
� 8 protons (+)
� 10 electrons (-)
-1
-2
Isoelectronic
� Isoelectronic – two atoms/ions that have the same electron configuration
� Cl-1 – 1s22s22p63s23p6
� Ar - 1s22s22p63s23p6
� Ca2+ - 1s22s22p63s23p6
� F-1 – 1s22s22p6
� Ne - 1s22s22p6
� Na+1 - 1s22s22p6