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.

​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

​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.

​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.

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