Periodic Table of Elements
• Ch. 5 Sec. 2
Arrangement
• Increasing proton # (ATOMIC #) from
left to right.
Periods & Groups
• Period = horizontal row
– 7 periods on table
• Group or Family = vertical columns
– 18 groups on table
Periods & Groups
• Groups (18)
• Periods (7)
Using Periodic Table
• Has the following:
1. Element Name
2. Element Symbol (1
or 2 letters)
3. Atomic #
4. Atomic Mass or
Mass #
Atomic #
• PROTON #
– Helium - 2 p+
• P+ = e• So… Helium also
has 2 e-
Practice (don’t write)
• How many p+ and
e- does the element
have?
• 7 p+ and e-
Mass # or Atomic Mass
(Decimal)
• P+ plus No
• Ex: Helium has 4
(round off) p+ and no
• Atomic mass
minus atomic # =
no
• Ex: Helium - 4 (mass #)
minus 2 (atomic #) = 2
no
Mass # (don’t write)
• How many p+, no,
and e- does Lithium
have?
• Protons = 3
• Electrons = 3
• Neutrons = 7-3 = 4
Isotopes
•
•
1.
2.
3.
Isotopes = element with diff. # of no
Ex: Hydrogen - atomic # =1 (1 proton)
H-1 = protium - 0 n
H-2 = deuterium - 1 n
H-3 = tritium - 2 n
Isotopes of Hydrogen
More Practice (don’t write)
• How many p+, no, edoes C-12 have?
• 6 p, 6 e, 6 n
• How many p+, no, edoes C-14 have?
• 6 p, 6 e, 8 n
Atomic Mass
• Weighted average of all known isotopes
(why it’s a decimal)
• Ex: Cl-35 (75%) & Cl-37 (25%) on
Earth
• More Cl-35 so mass on Periodic Table
is closer to 35 (35.45)
Compounds & Ions
• Elements swap e- when making
compounds
• P+ always stay the same
Ions
• If outer shells are not full (2 in 1st shell,
8 in other shells) atom loses or gains e= ion
• Not neutral anymore
Cations
• Atoms with 1 or 2 e- in
outer shell lose e• Cations - lose e (-) and
makes atom (+)
• *The cat was positive
about his loss.
Anions
• Atoms with 6 or 7 e- in
outer shell gain to get
full
• Anions - gain e (-) and
make atom more (-)
Gained
Electron
Lithium (don’t write)
• Lithium - 1 valence
e• Not happy
• Gives 1 e- away and
has 2 in new outside
shell (full)
• Cation
Fluorine (don’t write)
• Fluorine - 7 valence
e• Not happy
• Gains 1 e- to get 8
in outer shell (full)
• Anion
Lithium and Fluorine Making a
Compound Using Ions
Lithium gave its electron
to Fluorine (both are full
in outer shell now)