1

Periodic Trends

2

• Early Design

• Changes

• developed by Dmitri Mendeleev in the mid-1800s – Organized elements

by mass into rows and columns

– Found elements in the same column had similar properties

• Columns called– Groups or Families

3

• Electron Configurations

• Horizontal rows called periods

• Elements now arranged by atomic number (not mass)

• Elements in the same group have similar electron configurations– 1st family all end in s1

– 2nd group all end in s2

• Etc.

4

• Atomic Radius Trends • Atoms on the left of a period are bigger than atoms on the right.

• Why?– Electrons in same

energy level– Elements gain a

proton each step to the right

• More protons = more positive charge = closer electrons

5

• Atoms at the bottom of the table are bigger than atoms at the top.

• Why?– Outermost electron level

increases• Electrons further away

from nucleus

• An up/down move in the periodic table is a much more important change in atomic size than a left/right move.

6

• Ionic Radius

• Ionic Radius Trends

• Ionic Radius Truths

• Distance from the nucleus to the outermost electron orbital

• Same periodic trends as neutral atoms

• Positive ions are always smaller than neutral atoms – Why?

• Less electrons than protons = greater pull toward nucleus

7

• negative ions are always bigger than neutral atoms – Why?

• More electrons than protons = less pull toward nucleus

8

• Ionization Energy

• Ionization Energy Trends

• The amount of energy required to remove an electron from an atom to make a positive ion.

• I.E. increases from left to right– Why? More protons =

greater pull on the electrons

• I.E. Increases from bottom to top– Why? Electrons

closer to the nucleus

9

• Electronegativity

• Electronegativity Trends

• The tendency for atoms of an element to attract electrons when they are chemically bonded to atoms of another element.

• “How strongly they attract electrons”

• The same as Ionization energy