Transcript Element - Brookwood High School

History of the Periodic Table
Chapter 6

Newland
Placed elements in order of increasing
atomic mass
 Realized that properties repeated
every 8th element  Law of Octaves
 Theory not accepted widely because
of ties to music


Mendeleev
Published first periodic table based on
atomic mass
 Also saw pattern of 8 and left blank
spots for elements not found yet

Soon people realized that the periodic table had
some exceptions to the repeating characteristics

Henry Moseley
Fixed the problem by ordering the
periodic table by atomic number
 Periodic Law- periodic repetition of
chemical & physical properties of
element when arranged by atomic
number


Families



Go up and down
Contain same number of valence electrons
Periods


Go side to side
Contain same number of energy levels
Ion:
Atom with a charge
• Cation
• Anion
– Ion with a positive
charge
– Created by losing
electrons
– Ion with a negative
charge
– Created by gaining
electrons
– 1A = lose 1 e- = +1
– 7A = gain 1 e- = -1
– 2A = lose 2 e- = +2
– 3A = lose 3 e- = +3
– 6A = gain 2 e- = -2
– 5A = gain 3 e- = -3
Predicting the Charges of Ions
Element
Na
Mg
P
O
Br
K
Ne
Li
C
P
e
e- distribution
Valence e-
Group
To be stable
P
E
charge
P+ N0 E- Element
Ion
Charge
Notation
Mass
Number
Atomic
Mass
Isotope