1. Periodic Trends

2. Atomic Radius Measure of how large an atom is.
Measured from the nucleus to the outer most energy level.

3. How does atomic radius change down a group?
It increases down the group.
Why?
Add energy level every time you move down.
More Energy levels = more electrons = larger atom

4. How does atomic radius change across a period?
It decreases across the period
Why?
More protons in the nucleus higher electrical force pulls electrons closer to nucleus.

5. The Periodic Table and Atomic Radius

6. Ionization energy
Ionization energy is the amount of energy needed to remove an electron from an atom

7. How does ionization energy change down a group?
The ionization energy decreases as you move down a group.
Why?
The size of the atom increases.
Electron is further from the nucleus.
Easier to get away – little attraction

8. How does ionization energy change across a period?
The ionization energy increases as you move from left to right across a period.
Why?
Attraction of the electron to the nucleus increases.
Harder to get away – Lots of attraction
Nuclear charge (protons) increases while shielding (electrons in lower E.L.) is constant.

9. Electronegativity: the ability of an atom to attract an electron.

10. Trends in Electronegativity
Electronegativity generally decreases as you move down a group.
Why?
Electrons further away from nucleus
Weaker attraction

11. Trends in electronegativity
Electronegativity increases as you move across a period.
Why?
Greater attraction of electrons to nucleus
Getting closer to full octet
Easy to attract another electron.