Valence Electrons and ionic Bonding

1
Valence Electrons and ionic Bonding
2
Valence Electrons

• electrons in the highest occupied energy level
• always in the s and p orbitals
• normally just a draw a circle to represent these
  two orbitals
• determines the chemical properties of an element
• usually the only electrons used in chemical bonds

3
(No Transcript)
4
http//wps.prenhall.com/wps/media/objects/476/4883
16/Instructor_Resources/Chapter_09/FG09_27-06un.JP
G
5
(No Transcript)
6
http//jade.ccccd.edu/mweis/Images/Fireworks20Dra
wings/240120related20drawings/drawings20in20fi
reworks/body,20cell,20tissue/body_chem/chem_drw_
atom_generic.png
7
(No Transcript)
8
(No Transcript)
9
Lewis/Electron Dot Diagrams/Structures

• electron dot structures/diagrams are used to show
  valence electrons
• each dot around the element symbol represents a
  valence electron

10
(No Transcript)
11

• B is 1s2 2s2 2p1
• 2 is the outermost energy level
• it contains 3 valence electrons, 2 in the s and 1
  in the p
• Br is Ar 4s2 3d10 4p5How many valence
  electrons are present?

12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
http//images.google.com/imgres?imgurlhttp//hype
rphysics.phy-astr.gsu.edu/hbase/pertab/imgper/econ
fig.gifimgrefurlhttp//hyperphysics.phy-astr.gsu
.edu/hbase/pertab/perlewis.htmlh267w512sz22
tbnid__EXctBwlG0Jtbnh66tbnw128hlenstart1
prev/images3Fq3DElectron2BDot2BDiagrams26sv
num3D1026hl3Den26lr3D
16
Ionic Charge

• when forming compounds, atoms tend to achieve the
  electron configuration of a noble gas (ns2np6)
• this means they want their highest energy level
  filled with 8 electrons the easiest way possible
• atoms of metallic elements lose electrons
  producing cations (positive ions)
• Ca becomes Ca2
• atoms of nonmetallic elements gain electrons
  producing anions (negative ions)
• Cl becomes Cl1-

17
e-


-
-
18
1
2
3-
3
4/-
2-
1-
0


  ...etc.   ...etc.
As it turns out, atoms bond together for a very
simple reason atoms like to have full valence
shells.
19

• for transitional metals, charges of cations may
  vary
• iron can be Fe2 or Fe3
• other elements fill some orbitals but dont quite
  get a noble gas electron configuration

20
http//www.iun.edu/cpanhd/C101webnotes/chemical-n
omenclature/images/polyions.jpg
21
Formation of Compounds

• usually composed oppositely charged metallic
  cations and nonmetallic anions
• form a compound with overall zero charge
• know as the rule of zero charge

- anions
cations
22
Na gives Cl one electron and now both atoms
have a full valence shell (electron configuration
of a noble gas)
23
(No Transcript)
24
(No Transcript)
25
Chemical Formula

• shows the kinds and numbers of atoms in the
  lowest whole-number ratio of ions in the ionic
  compound
• Na 1 Cl 1- ? NaCl
• Ca 2 Cl 1- ? CaCl2
• Mg 2 O 2- ? MgO

26

• Mg and N?
• it takes two nitrogens to combine with three
  magnesiums
• Mg3N2
• magnesium nitride

27

• Al and O

28
(No Transcript)
29
Na 1 F 1- ? NaF
30
(No Transcript)
31
Properties of Ionic Compounds

• high melting points
• can conduct electric currents when melted or
  dissolved in water
• will shatter if impacted or crushed