Periodic Trends

Elements in Groups have…
Similar properties
Mendeleev and Meyer
Simultaneously created periodic table idea
developed idea of atomic number
What is Eka-Silicon?
Mendeleev’s prediction of an element based on the periodic table’s trends that wasnt discovered then. Later found to be Germanium.
Effective Nuclear Charge

1. electrons are attracted to the nucleus and repelled by other electrons

2. Z eff = Z – S, Z is atomic number, s is inner core electrons

3. average electrical feild for one electron

How is the size of Atoms determined?
1. bonding radii (between covalent bonded nucleii)
Trends in Atom Size

periods = decreasing due to higher Z eff

groups = increasing due to higher n

Size of Ions depends on

1. nuclear charge AKA how many electrons it has gained/lost

2. number of electrons it has overall

3. what orbitals the electrons are in

Size of Cations
smaller than parents because outer electrons are removed and thus repulsion goes down
Size of Anions
larger than parents because electrons are added thus increasing repulsion
Trends in Ion Size

increases down groups because of an overall increase in size

Isoelectric Series

1. same number of electrons

2. sizes go down as charge gets higher because the higher the charge, the more electrons lost

Ionization Energy

1. amount of energy needed to remove otuer electron

2. increases with each new electron removed

 3. increases dramatically in inner core electrons

Trends in Ionization Energy

1. decreases as you go down groups smaller atoms are less willing to give up their electrons

2. increases across periods because of higher Zeff

Dicontinuities in Ionization Energy

1. easier to remove from p orbitals than s orbitals.

 2. easier to remove from filled orbital shells (/,/)

Electron Affinity

1. the ease with which an atom gains an electron

2. more (-) an affinity is, the easier it will lose electron

3. (+) affinity is unstable and will not form 

Trends in Eletron Affinity

1. across periods increases

2. same discontinuities as Ionization

Metal Properties

1. Shiny

2. good conductor of heat and electricity

3. cations in aqueous solutions

4. metal oxides are basic

5. tend to lose electrons

6. malleable


1. not shiny

2. brittle

 3. poor condutor

4. non-metal oxides are molecular and acidic

5. aniona in aqueous soutions

6. gain electrons


1. characteristics of both metals and non-metals

2. e.g. silicon is shinny but a poor conductor and brittle

Alkali Group Trends

1. soft metallic

2. only compunds in nature

3. decreasing melting points and densities

4. decreasing ionization energies

5. exo rxns with water

 6. bright colors in flames

7. rxns with O: Li-nothing, K, Rb,Cs-superoxides, others-peroxides

Alkali Earth Metals Trends

1. Higher densities and melting points than alkalis

2. lower ionization energues than alkalis

3. rxn-ness increases top to bottom

4. rxn w/ H2O: Mg-Steam only, Be-nothing, everything else easily.

Chalcogen Trends

1. O,Se,S = non-metals

2. Te = ,etaliod

3. Po = Metal

Oxygen Trends

1. 2 allotropes O2, O3 (dioxygen and ozone)

2. 3 anions O-2,O2-2,O2-1 (oxide, peroxide, superoxide)

3. tends to take elctrons

Sulfur Trends

1. weaker oxidizer than O

2. allotrop S8 = ring shaped, most stable

Halogen Trends

1. non-metals

2. large (-) affinities

3. easily oxidized

4. react w/ metals = halidies

Trends in Noble Gases

1. large ionization energies

2. (+) affinities

3. unreactive

4. monotomic gases

5. Xe = XeF2, XeF4 and XeF6

6. Kr = KrF2

7. HArF – unstable, synthesized in 2000

Trends in Effective Nuclear Charge

1. Periods- increases because the atomic number increases (total electrons) while the s stays the same

2. Groups- stays basically the same

Rule for losing electrons (electron configuration-wise)
orbitals with lowest n level first ALWAYS, even if 3d does come after 4s.

1. Doesnt really belong to any group

2. Very hard to take it’s electron –no sheilding effect/repulsion from other electrons

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