1. TRENDS in the PERIODIC TABLE
A trend is a pattern or a repetition of particular properties.
Trends of the periodic table include
Atomic Mass, Atomic Radius, Net Nuclear Charge, Ion Size, Metallic or Non-Metallic Property, Electro-negativity,
1st ionization energy

2. The periodic table is arranged in a certain way to keep elements with similar properties close together

3. GROUPS vs. PERIODS Groups go up and down. Periods go left and right.
Groups share many similarities.
Periods show periodically (regularly) changing properties.

4. THERE ARE SEVERAL BASIC TRENDS (or patterns) THAT WE NEED TO RECOGNIZE AND UNDERSTAND.

5. These Trends are…
Atomic Mass (in amu)
Atomic Radius (size in picometers)
Net Nuclear Charge (how many protons are in the nucleus of an atom?)
Ion Size (cations and anions)
Metal Properties and Non Metallic Properties
Electronegativity
1st Ionization Energy levels

6. Demetri Mendeelev
Developed the first real periodic table which ours is based upon.
He was able to predict the missing elements and their properties once the table was put together.

7. Mendeelev was a genius!
Many of his predictions came true, such as the existence of “eka-aluminum” which we know as gallium. A missing element in his table made him believe that an element with certain properties belonged there.
By looking specifically for this missing “eka-aluminum”, chemists were able to discover gallium.
His predictions were quite close to the actual values of the various properties he quoted, such as mass, density, ionic formula, and others.

8. Our FIRST Trend Atomic Mass
Atomic mass goes higher from element to element, with few exceptions.
The Group Trend is that atomic mass increases.
The Period Trend is that atomic mass increases too.

9. Because of specific properties...
our Periodic Table has a non-regular shape. The elements are arranged by properties rather than a way just make the table be uniform in shape.

10. The Alkali Metals are in Group 1 but Hydrogen is not in this group.

11. Alkaline Earth Metals are in Group 2

12. TRANSITIONAL METALS are in Groups 3 - 12

13. INNER TRANSITIONAL METALS are at the bottom and fit in as shown

14. NON-METALS are at the right hand side of the table

15. Noble Gases are at the far right, group 18

16. OUR SECOND TREND Atomic Radius or Atom Size
If you follow along Table S for atomic radius, you find:
The Group Trend for atomic radius is that it increases down a group.
The Period Trend for atomic radius is that it decreases left to right.

17. • Period Trend for Atomic Radius Li Be B C N O F Ne 2-1 2-2 2-3 2-4
2-5
2-6
2-7
2-8 •
Atoms get smaller as you go across a period.
They gain electrons in the same energy levels, not getting bigger.
The additional positive charge from the additional protons pulls the electron orbital slightly tighter for each atom going across the period.

18. SHOWS Atomic Sizes for Groups and Periods

19. Metallic or Non-Metallic Properties
Someone, somehow, determined that “the most metallic metal” was Francium, bottom left hand corner of the Periodic Table.
They also came to the conclusion that Helium was to become known as the “most non-metallic” element.
You have to remember that, and you have to be able to compare up to 4 elements at a time and see which is closer to either Fr or He, and decide which is the most metallic, or most non-metallic.

20. The NEXT TREND is 1st IONIZATION ENERGY

21. First Ionization Energy,
It is the amount of energy needed to remove a valence electron from an entire mole of atoms and make them all into +1 ions.
For example…
To turn a mole of Li atoms into a mole of Li+1 ions, it would take (look at Table S now) kJ/mole

22. Time for an Example… Na has a first ionization energy of 496 kJ/mol
That means to take an outer electron from an entire mole of sodium atoms, it would take 496 kJ for the mole.

23. FIRST IONIZATION ENERGY FOR SOME SELECTED ATOMS
Going across the 3rd period, the trend for 1st Ionization Energy is to INCREASE.
FIRST IONIZATION ENERGY FOR SOME SELECTED ATOMS
Na 496 kJ/mol
Mg 736 kJ/mol
Al kJ/mol
Si kJ/mol
P kJ/mol
what about Mg to Al then???

24. The Mg - Al EXCEPTION is one of those unusual places where the periodic table cannot manage to be perfect for all properties.
Still, “the trend” is that first ionization energy increases when going across any period.
It’s a trend to wear a tuxedo to the high school prom. But it’s an exception to wear a color like these guys!

25. Ionization Energy
just so you know, there are first, second and third ionization energy levels.
each is measured with the unit kJ/mol
the “first” is the energy required to remove the first electron
the “second” is to remove an additional electron from the mole of ions (+1 cations into +2 cations, this is not in Regents Chemistry.)

26. Another Trend – Ionic Sizes
Atomic size
atoms get bigger going down a group
atoms get smaller going across a period
Cations are always smaller than atoms because the cations lose a whole orbital when they form.
Anions are bigger than the atoms they started as, because by adding electrons into the outer orbital, they must stretch a bit larger to accommodate those extra negative charges that push against each other.

27. when going down a group the ions get bigger
Cs+1 is larger than K+1
Br-1 is bigger than Cl-1
when going down a group the ions get bigger
This is true for cations & anions
K+1
Cs +1
Cs+1

28. GOING ACROSS A PERIOD
CATIONS get smaller
ANIONS get smaller too.

29. Linus Pauling electro-negativity scale.
the measure of the attraction an atom has to gain an electron in a chemical reaction.
It’s measured on the
Linus Pauling electro-negativity scale.

30. Fluorine and E-N
Fluorine tops out the scale at 4.0
Pauling set this standard, because he could.
It’s a totally arbitrary scale, based upon Fluorine and at 4.0 just because. All other atoms are compared to that one.
All the other electro-negativity values are relative to Fluorine’s

31. Electro-negativity is the amount of pull that an atom has for another electron in a bonding situation. Fluorine has the greatest desire of all atoms for that electron gain. Fluorine is given the rating of 4.0 on the E-N scale, the highest Electronegativity of all elements.
Electro-negativity is on Table S. You don’t have to memorize the trend, you can look it up anytime you want to.

32. Trends in Electro-negativity
Going down a group the trend is towards LOWER E-N values.
Going across a period the trend is towards higher E-N values.
It is all about HOW CLOSE IS THE ATOM TO FLUORINE which determines the relative electro-negativity.