1. Periodic Table Trends

2. 1. Atomic Radius
- the electron cloud surrounding the nucleus is based on probability and does not have a clearly defined edge.
- Generally, the total distance from an atoms nucleus to its outer most shell

3. - Moving from L  R the atomic radius decreases
Trend within Periods
- Moving from L  R the atomic radius decreases
- As we look from left to right the positive charge in the nucleus increases which increases the attraction between the protons and electrons
- True, we do add more electrons as well but not another shell
13 pulling tighter
17 pulling tighter

4. Trend Down a Group
The atomic radius increases moving down a group
More protons are added, more electrons are added, but are placed in another shell
- Some electrons might “shield” other electrons from proton attraction

5. Shielding: repulsion between two or more negative electrons in various shells causes the shells to be further away and therefore less strongly connected to the nucleus

6. Exception: Hydrogen has the smallest atomic radius

7. 2. Ionization Energy Trend
Atoms can gain or lose 1 or more electrons to form ions
Ion: is an atom or a bonded group of atoms that have a positive or negative charge
Cations are positively charged, meaning that they have lost electrons
- When atoms lose electrons, they always become smaller

8. - Anions are negatively charged, meaning they have gained electrons
- The protons need to distribute an attraction over a greater number of electrons making the attractions a bit weaker than that of the neutral atom
- Anions have a greater atomic radius than neutral atoms

9. Ionization Energy: the energy required to remove an electron
1st Ionization energy: the amount of energy to remove the 1st electron
2nd Ionization energy: the amount of energy to remove the 2nd electron
- More energy is required to remove the 2nd electron than that of the first.
This is because the 1st electron would have been experiencing more shielding and a lesser attraction to the positive nucleus
1st Ionization energy
2nd Ionization
Energy

10. increases moving from L  R
Trend within Periods
increases moving from L  R
Just like atomic radius, As we look from left to right the positive charge in the nucleus increases which increases the attraction between the protons and electrons
- Therefore, it takes more energy to pry them away
13 pulling tighter
17 pulling tighter
Not as strong of a pull, so it is easier to pull one away

11. Trend Down a Group
ionization energy decreases moving down a group
More protons are added, more electrons are added, but are placed in another shell
Some electrons might “shield” other electrons from proton attraction
- This means it takes less energy to remove an electron

12. Mom has too many kids to watch and can’t keep a close eye on them all
as she has less kids to watch, it would be more difficult to nab them

14. increases when moving left to right
3. Electronegativity
Electronegativity: is an atoms ability to attract the electrons of another atom to it
Trend Within Periods
increases when moving left to right
- this is because as we move to the right of the periodic table, the atoms ability to attract electrons becomes stronger as they become closer to a full octet
Boron still needs 5 e- to have a full octet
Flourine only needs 1 e- to have a full octet

15. - decreases as you go down a group
Trend Down a Group
- decreases as you go down a group
- (F) is the most electronegative element
EXCEPTION: Nobel gases have a full octet and are not looking to add e-

17. 4. Metallic Character Trend for Metals
Metallic Character – how readily an atom can lose an electron
Trend Within Period
From L  R Metallic Character decreases because the attraction between electrons and - the nucleus is stronger
- This makes it more difficult to lose an electron
Example: Which element is more likely to lose electrons?
Lose 4?
Lose 1?

18. Trend Down a Group
Metallic Character increases down a group
Again, like atomic radius trend, More protons are added, more electrons are added, but are placed in another shell
Some electrons might “shield” other electrons from proton attraction
- This makes it easier for an electron to be lost

20. 5. Reactivity for Metals Trend
Reactivity: how likely or vigorously an atom is to react with other substances
Usually determined by how easily electrons can be removed
(Same as Metal Character)
Trend Within Period
- From L  R reactivity decreases because the attraction between electrons and the nucleus is stronger
-This makes it more difficult to lose an electron, therefore less reactive

21. Halogen Reactivity Trend Down a Group
Reactivity increases down a group
Again, like atomic radius trend, More protons are added, more electrons are added, but are placed in another shell
-Some electrons might “shield” other electrons from proton attraction
- This makes it easier for an electron to be lost, or become more reactive
Halogen Reactivity

22. Reactivity
Reactivity