1. Periodic Trends

2. As we move across a period or down a chemical family, there are regular changes in elemental properties
Atomic Radius
Ionization Energy
Electronegativity
Periodic Trends

3. The outer boundary of an atom depends on the size of a cloud in which electrons spend approximately 90% of their time
The size of an atom

4. The volume of an atom is the result of a cloud of electrons.
What affects the size of an atom’s electron cloud?
The size of an atom

5. What trends do you see?

6. As we move down a family…
The number of energy levels (n) increases, the outer electrons will be further from the nucleus and so the atoms become larger
As we move down a family…

7. What trends do you see?

8. As we move across a period…
The atomic number increases and therefore the number of protons increase.
The electrons feel more nuclear charge and are pulled closer to the nucleus and the atom becomes smaller.
The charge felt by the electrons is called effective nuclear charge or “Zeff”
As we move across a period…

9. Ionic Radius

10. The energy required to remove an electron from a neutral atom
Atom  Ion+ + e-
The amount of energy required to move an electron from the outer most orbital to n = ∞
Ionization Energy

13. Ionization energy tells us how strongly an atom holds onto its outermost electrons
A large atom has outer electrons that are held less tightly (smaller atom holds onto electrons more strongly)
Ionization Energy

14. Ionization Energy As atomic radius increases…
Electrons held less tightly
Requires less energy to remove an electron
Ionization energy decreases
As atomic radius decreases…
Electrons held more tightly
Requires more energy to remove an electron
Ionization energy increases
Ionization Energy

15. Ionization Energy Trend

16. Electrons are not only REMOVED from atoms but are also ATTRACTED to form bonds between atoms
The ability for atoms to attract electrons is called…
Electronegativity

17. Electronegativity As atomic radius increases…
Nuclei further from bonding electron
Has lower ability to attract electron
Electronegativity decreases
As atomic radius decreases…
Nuclei closer to bonding electron
Has higher ability to attract electron
Electronegativity increases
Electronegativity

18. Trends in Electronegativity

19. General Trends