Periodic Trends

Periodic Trends

What are valence electrons? • Valence electrons are the electrons in the outer-most energy level of an atom. • Elements with a full valence shell (8 electrons) are the most stable.

Group

Family Name

1 2

Alkali metals Alkaline Earth metals

13 14 15 16 17 18

Oxygen group Halogens Noble gases

# valence electrons 1 2

3 4 5 6 7 8

Periodic Trends • From left to right across periods 1-3: – Atoms of all these elements contain one more valence electron than the previous element

• From top to bottom within any group: – Atoms of all of the elements in a given group contain the same number of valence electrons

Periodic Trends (cont) • Periodic trends in the number of energy levels: – From left to right across any period: • Atoms of all elements in a given period have the same number of energy levels

– From top to bottom within any group: • Atoms of each element in any given group have one more energy level than the element above