1. Periodic Table and Periodic Law
Chapter 6
Periodic Table and Periodic Law

2. The Periodic Table got its name because of the repeating pattern of chemical & physical properties.
Mendeleev ordered his periodic table with elements arranged in order of increasing atomic mass.

3. He started new rows so that the elements having the same properties would be aligned in each column.
Mendeleev left “holes” for elements he predicted, but weren’t discovered until a later time.
Similar properties in each column
Holes for undiscovered elements

4. In the modern Periodic Table, elements are arranged in order of increasing atomic number.

5. The horizontal rows are called periods.

6. The vertical columns are called groups.

7. The patterns of properties repeat in each new row, so elements in the columns, have similar chemical and physical properties. This is called the periodic Law.
Similar properties in each column

8. The group A elements (the s&p blocks) are called the representative elements.
1A 2A A 4A 5A 6A 7A 8A

9. The group B elements (the d block) are called the transition elements.
The group B elements (the f block) are called the inner transition elements.
Transition
Inner
Transition

10. There are 3 main classes of elements: metals, nonmetals, metalloids.

11. Metals, Nonmetals, Metalloids
There is a zig-zag or staircase line that divides the table.
Metals are on the left of the line, in blue.
Nonmetals are on the right of the line, in orange.

12. Metals are located on the left side of the Table
Metals are located on the left side of the Table. Metals are generally shiny solids, good conductors of heat and electric current, and have high melting and boiling points.
They are also malleable and ductile.

13. Metals
Metals are lustrous (shiny), malleable, ductile, and are good conductors of heat and electricity.
They are mostly solids at room temp.
What is one exception?

14. Located on the upper right side of the table, nonmetals are generally gases or brittle solids at room temp, and poor conductors.

15. Nonmetals Nonmetals are the opposite.
They are dull, brittle, nonconductors (insulators).
Some are solid, but many are gases, and Bromine is a liquid.

16. The elements that border the heavy stair-step line on the table are called metalloids, which have some characteristic of both metals and nonmetals.

17. Metalloids Metalloids, aka semi-metals are just that.
They have characteristics of both metals and nonmetals.
They are shiny but brittle.
And they are semiconductors.
What is our most important semiconductor?

18. The electron structure of an atom determines many of its chemical & physical properties. For the group A elements, the group number equals the number of valence electrons.
(Except for Helium=2)

19. The Octet rule states that atoms lose, gain, or share electrons in order to gain a full set of 8 valence electrons.
This noble gas configuration is very stable. (the exceptions are Hydrogen and helium which will have a stable set of 2 electrons in the 1st energy level). Using the octet rule, you can predict which ions will likely form.
Neon has full outer
shell : stable &
nonreactive

20. Metals are electron donors
Metals are electron donors. They tend to lose electrons and become + charged ions. Called a cation.
Must lose 1 electron to have full outer shell (easier to lose 1 than gain 7)
Na has 1 valence electron
Creates a ion with a +1 charge

21. Nonmetals are electron acceptor
Nonmetals are electron acceptor. They tend to gain electrons and become – charged ions. Called an anion.
Need 1 more electron to gain full outer shell
Chlorine has 7 valence electrons
Creates -1 ion

22. Na Cl

23. Periodic trends
Atomic radius: Tends to decrease across the period. Electrons are being added in the same energy level so increased attraction between the larger number of + protons pulls the – electrons closer.

24. Periodic trends
Atomic radius: Tends to increase down the group, because you are adding energy levels, which shield the valence electrons from the pull of the nucleus.

25. Ionic radius
Losing electrons produce + charged ions, which are smaller than the parent atom.

26. Cation Formation
Effective nuclear charge on remaining electrons increases.
Na atom
1 valence electron
Remaining e- are pulled in closer to the nucleus. Ionic size decreases.
11p+
Valence e- lost in ion formation
Result: a smaller sodium cation, Na+

27. Ionic radius When atoms gain electrons, they
become – charged ions, which are larger than the parent atom.

28. Anion Formation
A chloride ion is produced. It is larger than the original atom.
Chlorine atom with 7 valence e-
17p+
One e- is added to the outer shell.
Effective nuclear charge is reduced and the e- cloud expands.

29. Ionic radius
As with the atomic radius size, decrease across the periods an increase down the group.
Notice difference between cations & anions; but trends are still same
decreases
increases

30. Ionization energy
Is the amount of energy required to pull the 1st valence electron away from the atom. Elements with high ionization energy are [unlikely, likely] to lose electrons. Atoms with low ionization energy [easily, don’t really] lose electrons

31. Ionization energy
Generally metals have low ionization energies and easily form positive ions… nonmetals have high ionization energies and tend to form – ions.
Noble gases: do not form ions
Mostly +2 & +3

32. Ionization energy
Ionization energies increase across the period, because the atoms are getting smaller and the electrons closer to the nucleus and harder to pull away.
Increases

33. Ionization energy
Ionization energies decrease moving down the group because the size of the atom is larger so the electrons are farther away and easier to remove.
In other words the outer
electrons are shielded from the pull of the nucleus by the inner shells
decreases

34. Electronegativity
Indicates the elements relative ability to gain electrons in a chemical bond. The greater the electronegativity the greater the attraction for electrons.
How strongly the element “wants” the electron, so metals are low; nonmetals are high

35. Electronegativity
Fluorine is the most electronegative element are Francium is the least. Increases across the periods and decreases down the group.
increases F
decreases Fr

37. Noble
Gas