Periodic Trends

Valence electrons are electrons in outermost incomplete shells.

If you skip the transition metals, you can count valence electrons by counting groups.  

Transition metals have 2-3 valence electrons.

Valence Electrons

​10th Grade: Use the chart below to update your valence electron worksheet. Skip transition metals

​Atomic radius increases as you go down a group and decreases as you go across a period

Multiple Choice

Atomic radius DECREASES when

• when you go across a row from right to left

• when you go down a group

• when you go across a row from left to right

• when you go across a group from left to right

Reorder

Put in order from biggest to smallest (decreasing size)

• Calcium

• Iron

• Zinc

• Bromine

• Krypton

1

2

3

4

5

• 1
• 2
• 3
• 4
• 5

Open Ended

Why does atomic radius decrease as you go across a period?

Open Ended

Why does atomic radius increase as you go down a group?

Multiple Choice

Which is the smallest

• chlorine

• chlorine ion

• aluminum ion

• magnesium ion

Reorder

Put these ions and atoms in order from biggest to smallest (DECREASING SIZE)

• nitride ion (nitrogen ion)

• oxide ion (oxygen ion)

• fluoride ion (fluorine ion)

• neon atom

1

2

3

4

• 1
• 2
• 3
• 4

Multiple Choice

Ionization energy ________________ as you go DOWN a group

• increases

• decreases

Multiple Choice

Which atom has larger ionization energy

• aluminum

• sulfur

Multiple Choice

Which atom has smaller ionization energy

• strontium

• iodine

​Electron Affinity

​Energy released when an electron is ADDED to an element.

Affinity means a preference or something that you like. Elements with high electron affinity want to or are more likely to take electrons from other elements.

Non-metals have higher electron affinities than metals.

Electron affinity INCREASES as you go from left to right across a period and DECREASES as you go from top to bottom down a group.

Multiple Choice

This element has the lowest electron affinity

• magnesium

• sodium

• silicon

• sulfur

Multiple Choice

This element has the highest electron affinity

• iron

• calcium

• chlorine

• radon

​Electronegativity

​Recall, molecules are groups of atoms that SHARE electrons.

Only valence electrons are involved in forming these “shared electron bonds” (covalent bonds)

Atoms within a molecule do not always share electrons equally.  Some pull them closer to themselves than others. 

Electronegativity is a measure of how strongly the atoms within a molecule attract the electrons shared between them.

Increases as you go left to right across a period.
Decreases as you go from top to bottom down a group.

Multiple Choice

What element is the most electronegative

• fluorine

• bromine

• iodine

• astatine

Multiple Choice

What element is the LEAST electronegative

• cadmium (Cd)

• antimony (Sb)

• Zirconium (Zr)

• Francium (Fr)

​the impulse for which a chemical substance undergoes a chemical reaction, either by itself or with other materials

Multiple Choice

What metal is most reactive

• lithium

• sodium

• potassium

• rubidium

Multiple Choice

What non-metal is the most reactive

• iodine

• sulfur

• oxygen

• fluorine