Periodic Table

1
Periodic Table

• Section 18.3

2
Periodic Table

• Periodic- Repeated in a pattern
• Elements are ordered by
• increasing atomic number
• changes in physical chemical properties
• Mendeleev- Ordered elements by atomic mass
• Left blank places in his table to line up
  elements according to their properties
• Elements were later discovered and fit into the
  places he left blank

3
Mendeleev
4
Periodic Table

• Moseley- organized elements by atomic number
  rather than atomic mass
• Same arrangement as today
• Groups/Families- vertical columns of the periodic
  table
• Rows of Periodic Table- periods
• Electrons
• Around the nucleus in an electron cloud
• Energy levels dictate location of electrons
• Closer to nucleus less energy
• Fill energy levels from inner to outer levels

5
Electrons

• Electrons in outer shell determine chemical
  properties of elements
• Complete outer shell- needs 8 electrons to be
  stable
• Energy levels and of electrons in each
• Level 1 Holds 2
• Level 2 Holds 8
• Level 3 Holds 18
• Level 4 Holds 32

6
Energy levels of electrons

• Sublevel e in sublevel Shape
• s 2 sphere
• p 6 dumbbell
• d 10 double dumbbell
• f 14 complex
• http//library.thinkquest.org/3659/structures/shap
  es.html

7
Energy levels of electrons

• Level 1 s 2 electrons
• Level 2 s p 2 6 8 electrons
• Level 3 s, p, d 2 6 10 18 e-
• Level 4 s,p,d,f 2 6 10 14 32 e-
• Valence Electrons
• Group 1A 8A have 1-8 valence electrons

8
Periodic Table, Valence electrons, and Diatomics
9
Dot Diagrams

• Electron dot diagram (or Lewis dot diagram) - A
  symbol of an element surrounded by dots to
  represent electrons in the outer energy level
• First 2 electrons go together
• Next electrons go one on each side, then start to
  double up

10
Valence electrons

• http//www.ausetute.com.au/lewisstr.html
• Properties of elements in the same group- similar
  due to same of valence electrons
• Alkali metals- group 1A- very reactive metals
• Alkaline metals- group 2 A- less reactive than
  alkali
• Halogens- group 7A
• Likely to react with Alkali metals- group 1A

11
Arrangement of Periodic Table

• Noble Gases- group 8A- not reactive- dont form
  compounds