Periodicity

Periodic Table Trends

Describing the Periodic Table

periodic law: the properties of elements repeat every so often

period:

group (family):

horizontal row; there are 7

vertical column; there are 18 18

1716151413

129 10 1187654

1

3

21

2

34

6

7

5

alkaline earth metals

halogensnoble gaseslanthanides

alkali metals actinidescoinage metalstransition elements

main block elementsmetalloids

hydrogenmore nonmetals

more metals

Ionization Energy

• Ionization Energy: The energy required to remove an electron from an atom or ion

• As you move down a group/family, the energy levels become higher and the electrons are further from the positively charged nucleus, so it is easier for an electron to leave the atom. The ionization energy decreases.

Ionization Energy 2

• Electron shielding: the reduction of the attractive force between a positively charged nucleus and its outermost electrons due to the cancellation of some of the positive charge by the negative charges of the inner electrons. – English: too many electrons repel each other

away from the nucleus.

Ionization Energy 3

• Ionization energy increases as you move from left to right across the table. Every element you move across has another proton so the outer electrons become more attracted to the nucleus and harder to remove from the atom.

Ionization Energy 4

Atomic Radius

• Bond Radius: ½ the distance from center to center of two like atoms that are bonded together.

Atomic Radius 2

• Due to increasing number of energy levels as you travel down a group/family, the radius becomes larger

• As you move across the periodic table, the electrons are more attracted to the nucleus and their radius becomes smaller

Atomic Radius3

Electronegativity• Electronegativity: a measure of the ability of

an atom in a chemical compound to attract electrons

• As you move down a group/family, energy levels are added and electrons are further from the nucleus. Electron shielding prevents the atom from attracting another electron.

• As you move across the periodic table, the shielding remains the same, but more protons increases the attraction for more electrons so the electronegativity increases.

Electronegativity2

Summary of Periodic Trends

Ionic size (cations) Ionic size (anions)decreases decreases

Shielding is constantAtomic radius decreasesIonization energy increasesElectronegativity increasesNuclear charge increases

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