Electrons and IonsUnit 3

Electron Energy LevelsWhat are electrons and

where are they located? Small negatively charged

particles Located in the orbitals

Energy level determines electrons energy

Can move from one energy level to another Absorb energy = jump to

higher level Give off energy = jump to

lower level

What are Valence Electrons? Definition:

Electrons found in the outer energy level of an atom Can participate in interactions with other atoms Determine properties of atoms

Atoms are most stable when outermost energy level is full Which atom pictured below would be most stable?

How do you determine valence electrons?

Valence electrons increase across periods from left to rightAll elements in the same group have the same number of

valence electrons

How can you represent valence electrons?Electron dot diagrams are used to represent valence

electrons An elements chemical symbol is surrounded by dots that represent

valence electrons Elements have a maximum of 8 valence electrons

How do valence electrons determine reactivity?

Elements in groups 1, 2, 6 and 7 are highly reactiveElements in group 1 and 2 want to give up their valence

electrons to become stableElements in groups 6 and 7 want to gain valence

electrons to become stable

Elements in group 8 (noble gases) have full outer shell of electrons and are very stable/non-reactive

What are ions?

Why are atoms electrically neutral?Equal numbers of protons and electrons

When atoms gain or lose valence electrons they become charged

Definition: Ions are atoms that have positive or negative charge due

to unequal numbers of protons and electrons

How can you tell the charge of an ion?

Ions charge is identified by their group (column) number

IonsWhen atoms lose valence electrons they become positively chargedHave more protons than electrons

Called “Cations”

When atoms gain valence electrons they become negatively chargedHave more electrons than protons

Called “Anions”