ATOMIC STRUCTURE
P+ = PROTON
No = NEUTRON
E--- = ELECTRON
DIFFERENT WAYS TO WRITE ELEMENTS & THEIR
SYMBOLS
 Phosphorus—31 AND 3115P





 ***NEUTRONS = mass # -- atomic #
 ***isotopes--- atoms of the same element but with different
numbers of neutrons (different mass #s)
 Ex: P—32 and P—30
Ex: phosphorus—31
Protons = 15
Electrons = 15
Neutrons = 16
 NUMBER THESE COLUMNS ON YOUR PERIODIC
TABLE:
1
2
13
16
17
 (1A)(2A) (3A)
(7A)
14
18
(4A)
(8A)
15
(5A)
(6A)
 Vertical columns—groups or families
 --- there are 18 total (8A groups and 10B groups)
 Horizontal rows—periods or series

---there are 7 rows total
 VALENCE ELECTRONS-- the outermost electrons having
the highest amount of energy and are farthest from the
nucleus and the ones involved in chemical reactions
 ** # of valence electrons = “A” column # on the periodic table

(“A” group #)
 ** # of energy levels = row # on the periodic table
 Ex: Beryllium (Be): column 2A= 2 valence electrons

Row 2 = 2 energy levels
 Ex: Phosphorus (P): column 5A = 5 valence electrons

Row 3 = 3 energy levels
 ATOMIC MATH PROBLEM
 1.
Take the # of protons in oxygen X the # of




electrons in fluorine = _______________
2. Take this number --- # of neutrons in chlorine
= _________________
3.
Take this number + silicon’s atomic # =
____________
4.
Take this number / # of neutrons in helium
= _____________
5.Take this number --- aluminum’s mass # =
_____________
Atomic Math Problem #2
1.
2.
3.
4.
5.
6.
Take sodium’s mass # and subtract its proton number.
Take this number and divide by carbon’s neutron
number.
Take this number and multiply by calcium’s electrons.
Take this number and divide by boron’s proton
number.
Take this number and multiply oxygen’s neutron
number.
Take this number and subtract zinc’s mass number.
Calculating average atomic
mass using % abundance
information
 atomic mass-the average mass of all of an
element's isotopes; you round this to
actually get the mass number
***every element has at least 2 isotopes
* **the most abundant isotope matches
the mass # from the periodic table!!
Ex: Which is most common?
O-16
O-17
O-18
 Hydrogen has 3 known isotopes:
H-1 (protium) occurs 99.9885% of the time with an
atomic mass of 1.0078 amu
H-2 (deuterium) occurs 0.0115% of the time with an
atomic mass of 2.0141 amu
H-3 (tritium) is synthetically made
MASS OF EACH ISOTOPE X DECIMAL FORM
OF
THE % OF THE
TIME
IT OCCURS
(1.0078 X 0.999885 ) + (2.0141 X 0.000115)
1.007684103 + 0.000231622
1.007915725 amu
Calculate avg. atomic mass for
“element Z”
Z—10 occurs 75.5% of the time
Z—11 occurs 20.5 % of the time
Z—12 occurs 4.0 % of the time
(10 x 0.755) + (11 x 0.205) + (12 x 0.040)
10.285 amu