1. Honors Chemistry Enloe High SChool
Periodic Trends
Honors Chemistry
Enloe High SChool

2. Element’s Electron Configuration
Elements in the same column have similar valence electron configurations
As a result, elements in the same column have similar chemical properties
This also helps us understand the periodic trends

3. Atomic Radius
Half the distance between the nuclei of two atoms of the same element that are bonded together
Atomic radius decreases as you move from left to right across the periodic table
Effective nuclear charge: The net positive charge experienced by an electron in a many electron atom

4. Atomic Radius
Atomic Radius increases as you move down a group in the periodic table
This is because the valence electrons are in higher energy levels farther from the nucleus

5. Atomic Radius

7. Ionic Radius Cations Anions Cations are smaller than parent atoms
Cation sizes generally increase from right to left
Cation sizes increase down a family
This is caused by having more protons than electrons
Anions are larger than parent atoms
Anion sizes generally increase from right to left
Anion sizes increase down a family
This is caused by having more electrons than protons

9. Atomic/Ionic Radius Examples
Select the larger species in each of the following pairs:
Kr or Xe
Si or P
Arrange the following in order of increasing size
N3-, O2-, F1-

10. Ionization Energy
Minimum energy required to remove an electron from an isolated gaseous atom
Requires more energy as you remove more electrons
Ionization energy increases when:
Moving left to right across the period
Moving from the bottom to the top of a group
This is because the attraction between the electrons and the nucleus increases

12. Ionization Energy
Once an atom has filled it’s octet, there is a noticeable increase in ionization energy
Na 1st ionization energy is 496 kJ/mol
Na 2nd ionization energy is 4,560 kJ/mol
This is because a core electron is being removed rather than a valence electron

13. Ionization Energy Magnesium 1st ionization energy is 738 kJ/mol
Aluminum 1st ionization energy is 578 kJ/mol
This drop is due to Al having a partially filled p orbital (Think electron configurations)

14. Ionization Energy
Arrange the following in order of increasing first ionization energy:
S, Cl, Se, Br
Which atom has the lower first ionization energy
Al or B
O or C

15. Electronegativity
The ability of an atom in a molecule to attract electrons to itself
Electronegativity increases when:
Moving from left to right across a period
Moving from the bottom to the top within a group
Caused by the nucleus wanting to hold onto electrons more tightly
Electronegativity does not apply to noble gases

17. Metallic Properties Low ionization energy Low electronegativity
Large atomic radius/cation radius
Have luster or shine
Malleable and ductile
Great conductors of heat and electricity
Most have fewer than 3 valence electrons

18. Metallic Character
Property used to determine how metallic an element will behave
Increases when:
Moving from right to left across a period
Moving from top to the bottom of a group
This can be explained by the periodic trends

20. Nonmetallic Properties
High ionization energy
High electronegativity
Small atomic/anion radii
Dull and brittle solids
Poor conductors of heat and electricity
Most have 5 or more valence electrons

21. Nonmetallic Character
Property to describe how nonmetallic an element will behave
Increases when:
Moving from left to right across a period
Moving from bottom to top within a group
This is due to the periodic trends

23. Metallic and Nonmetallic Character
Which of the following is the more active element:
K or Rb
Na or Al
F or Br
As or Se

24. Oxidation State/Number
A positive or negative whole number assigned to an element in an ion or molecule
For our purposes it will be the same as the charge for an ion
Depends on the number of valence electrons an atom has

25. Oxidation State/Numbers
Some elements can have multiple oxidation numbers
Transition metals have multiple oxidation numbers because of the d orbitals
Metalloids and other elements along the staircase depend on what they are bonded to

26. Oxidation States/Number
Assign oxidation numbers to the following elements: Ca S Mn As

27. Electron Configuration for Ions
For representative elements we will always add or remove electrons from the highest s or p orbital
For transition elements follow this order
Highest p, then highest s, and lastly highest d

28. Electron Configuration for Ions
Cations
Anions
Ion that is positively charged
Always lose electrons from the valence shell
Metals tend to form cations
Ion that is negatively charged
Always gain electrons
Nonmetals tend to form anions