1. or in other words – let the chart do the work.
Periodic Trends
or in other words – let the chart do the work.

2. PERIODIC TRENDS OF THE ELEMENTS
TABLE ?
I INVENTED IT !
Chemical properties
Physical properties
Atomic radii
Ionic radii
Ionization energy
Electron affinity
Electronegativity
Metallic & nonmetallic character
Mendeleev

3. DEFINITIONS OF PERIODIC PROPERTIES
Chemical properties refers to the tendency of atoms to combine with other elements and / or molecules to form compounds.
Physical properties refers to characteristics such as density, physical state (solid, liquid or gas), electrical and thermal conductivity, malleability (can be hammered into shape), ductility (can be stretched), color, luster (shininess), brittleness, etc.

4. Definitions of periodic properties (cont’d)
Atomic radii is measured as one half of the distance between the nuclei of two adjacent similar atoms (it measures atomic size)
Ionic radii is measured as one half of the distance between the nuclei of two adjacent similar ions (it measures ion size)
Ionization energy measures the energy needed to remove an electron from a free atom in the gas state (it measures how tightly electrons are bound to an atom)
Electron affinity measures the energy released when an electron is added to a free atom in the gas state ( it measures how well atoms attract electrons)

5. Definitions of periodic properties (cont’d)
Electronegativity measures the electron attracting ability of an atom when it is bonded to another atom
Metallic character measures the tendency of an element to act as a metal in things such as conductivity, tendency to lose electrons, shininess, maebility and ductility
Nonmetallic character measures the tendency of an element to act as a nonmetal in things such nonconductivity, tendency to gain electrons, low luster and brittleness.

6. General organization of the periodic table
Columns (families or groups) contain elements with similar valence electron configurations: ns1, ns2, ns2 np3, etc. and therefore similar chemical properties
Rows (periods or series) contain elements with valence electrons at the same energy level (n=1, n=2, n=3, etc.)
Blocks of elements contain atoms with the same valence electron orbital type (s, p, d or f)

7. Orbital Blocks on the Periodic Table
metals
non metals I N E R T G A S s B L O C K
p BLOCK
d BLOCK
f BLOCK
METALLOIDS

8. Common Chemical Families & Their Properties
Column I (Alkali Metals) Li Na K Rb Cs and Fr
Form +1 cations
Are highly metallic
Reaction readily and rapidly with water to form hydroxides and hydrogen gas
React with the halogens to form ionic salts with the formula type MX. For example: NaCl or KBr.
Valence Electrons are ns1
Column II (Alkaline Earth Metals) Be Mg Ca Ba Sr and Ra
Form +2 cations
React with the halogens to form salts with formula type MX2 (for example MgBr2 or BaCl2)
Valence Electrons are ns2

9. Common Chemical Familes & Their Properties page 2
Column VII (Halogens) F2 Cl2 Br2 I2 and At2
All are diatomic elements (occur as a
molecule consisting of two atoms
Are highly nonmetallic
React ready and rapidly with metals to form salts
Occur in all three phases at room temperature F2 and Cl2 are gases, Br2 is a liquid and I2 is a solid.
Valence Electrons are ns2 np5

10. Common Chemical Families & Their Properties page 3
Column VIII (Noble Gases or inert gases)
All are unreactive under ordinary conditions
All have completed outer energy levels
All are gases at room temperature and pressure
Their electron configuration is ( ns2 np6 ) This is a filled outer shell, which the other atoms attempt to achieve through chemical reactions and bonding.

11. CHEMICAL FAMILIES Alkali metals Halogens Alkaline Earth Metals C
C C
O O
L L
M M
U U
N N
I II C O L U M N V I
Transitional
Metals
LANTHANIDE SERIES
ACTINIDE SERIES

12. What factors determine the periodic trends of the elements ?
The number of protons and electrons an atom contains. (more protons create a greater nuclear charge which attracts electrons more strongly)
Distance separating the outer electrons (valence electrons) and the nucleus. (when electrons are closer to the nucleus they are held more tightly)
3. Pairing of electrons in the outer energy level orbitals. (paired electrons are more stable than unpaired electrons)

13. Periodic trends – Atomic Radii
As we move across a row (period) from left to right on the periodic table, atoms become smaller as the atomic number becomes larger. This increase in nuclear charge allows the nucleus to pull in the electrons more tightly and thereby reduce atomic size (radius).
As we move down a column on the periodic table, elements contain more electrons and more energy levels become populated resulting in an increase in atomic size (radius). Remember that completing a period on the periodic table results in a completed energy level within the atom.

14. Periodic Trends – Atomic Radii
SIZE OF ATOMS DECREASES S I Z E N C R A

15. Periodic Trends - Ionic Radii
Metal atoms lose electrons to form ions so they are smaller than the original atoms. In a sodium atom, the last electron is in the 3rd energy level, but when it is lost, the outer shell is now the second level.
Nonmetal atoms gain electrons to form ions. Since the number of protons doesn’t change, the electrons can’t be held as tightly and they are able to move further away.
Anions in the same period are larger than cations in that row.

16. Periodic Trends – Ionic Radii
Na+1 has 2 filled energy levels
K+1 has 3 filled energy levels 8e 2e
+11 8e 8e 2e
+19

17. Periodic Trends – Ionic Radii
The fluoride ion has 9 protons attracting the
the 10 electrons so there is more attraction
The nitride ion (N-3) has only 7 protons attracting 10 electrons so the electrons are not held as tightly and the ion is larger than the fluoride ion. 8e 2e +9 8e 2e +7

18. ? Periodic Trends – Ionic Radii Why is this important ?
Excellent question – glad you asked.
Explaining a lot of bonding and chemistry deals with two ideas.
Electronic Factors – Chemistry occurs because of the charge factors, this is why it is NaCl and not NaCl2
Steric Factors – Chemistry occurs because of the size of molecules, just like in our macro world. Medicines and body chemistry use this a lot.

19. Periodic Trends – Ionic Radii
SIZE OF IONS INCREASES S I Z E N C R A

20. Periodic Trends – Ionization Energy
The outer electron for the sodium ion is in the 3rd energy level so it is closer to the nucleus than the outer electron for the potassium ion which is in the th energy level The further away from the nucleus, the less force of attraction and the easier it is to remove that electron. 1e 8e 2e
+11 1e
18e 8e 2e
+19

21. Periodic Trends – Ionization Energy
Fluorine has two options to become an ion. It can gain 1 e to have a filled second shell or it can lose 7e-1 to have a filled first shell. It will always be the choice that deals with the lower number of electrons.
Sodium can either lose a single electron or gain 7 electrons to achieve a filled outer shell Remember that it is always deal with the lower number of electrons so Sodium will lose one electron and in this case form a positive ion. 7e 2e +9 1e 8e 2e
+11

22. Periodic Trends – Ionization Energy
Successive Ionization Energies
For a sodium ion to be formed, only one electron has to be removed, and it takes energy to remove the electron because it doesn’t just happen on its own. This energy is called the Ionization Energy.
For a magnesium ion to be formed, two electrons have to be removed. It would be simple if we can simply double the Ionization Energy but it doesn’t work that way. We need to have an Ionization Energy for the 2nd electron. After the first electron, the others are called successive ionization energies.
Different factors affect the value of the these energies and will be described on the next slide.

23. Periodic Trends – Ionization Energy Successive Ionization Energy
Distance from the nucleus. The closer the e-1 is to the nucleus the more energy is needed to remove it.
Proton to electron ratio. The more protons present in the nucleus, the more attraction and the more energy is needed to remove an electron.
Filled and half-filled sets of orbitals. Filled and half-filled sets of orbitals are more stable and therefore take more energy to remove an electron from them.
Shielding effect. Since magnetic attraction can’t move through magnetic material, electrons in inner shells, can block the attraction to the electrons in the outer shell, making it easier to remove those electrons.

24. Periodic Trends – Ionization Energy
Across a row, the Ionization Energy increases.
Down a column, the ionization energy decreases.

25. Periodic Trends – Ionization Energy Successive Ionization Energies
The Blue line occurs when the next electron being removed is from an inner shell.

26. Periodic Trends – Electron Affinity
Elements which are more nonmetallic (to the left & up on the periodic table) have greater electron affinity.
Those which are more metallic (to the right & down on the periodic table) have lower electron affinity.

27. Periodic Trends – Electron Affinity
Across each row, electron affinity increases.
Down a column, electron affinity decreases.

28. Periodic Trends - Electronegativity
Electronegativity is the ability of an atom to grab onto the shared electrons in a bond.
Flourine has the highest electronegativity value of 4.0
This concept was developed by Linus Pauling (2 unshared Nobel Prizes). It was devised by comparing the different bonds to each other, then when fluorine was discovered to have the highest value he assigned it a value of 4. There are no units !
As you move away from Fluorine, the values get lower.

29. Periodic Trends – Electronegativity (En)
Across each row, electronegativity increases.
Down a column, electronegativity decreases.