Chapter two
Modern periodic table
The long form periodic table:
It depends on the building up principle (Aufbau)
The elements are arranged in an ascending order according to their atomic
number (each element have one electron more than the element before it).
Remember!!!
An atom is the smallest particle of an element, containing positively charged
protons and neutral neutrons, in the nucleus, and negatively charged electrons
An atomic number is the number of protons in the nucleus of an atom
According to which property are the elements in the modern periodic table
organized left to right?
Answer
Elements are organized in the periodic table in order of increasing atomic
number, from left to right.
Groups and Chemical Behavior
The group number gives us information about the number of electrons lost or
gained by an atom of an element when it reacts.
The Periodic Table: s, d, p, and f Blocks
The periodic table can be divided into blocks. The blocks are the s,
d, p, and f blocks. These block where an element is located is
related to the arrangement of its atoms’ outermost electrons.
The periodic table is divided into four main blocks
1- S – block elements
2- P – block elements
3- d – block elements
4- f – block elements
Sequence of energy sublevels
1S < 2S < 2P < 3S < 3P < 4S < 3d < 4P < 5S < 4d < 5P < 6S <
4f < 5d < 6P < 7S < 5f < 6d
Description of long periodic table :
S – block
consists of two groups 1A & 2A, because the S – sublevel consists of one
orbital which is filled with two electrons only
P – block
consists of (6) groups (3A,4A,5A,6A,7A & zero group), because the P –
sublevel consists of three orbitals which filled with six electrons.
d – block
consists of (10) groups (3B,4B,5B,6B,7B,8,8,8,1B&2B), because the
d – sublevel consists of five orbitals which are filled with ten electrons.
It consist of three transition series:
1st transition series:
includes elements of sublevel 3d in the 4th period. Start with 21Sc to 30Zn.
2nd transition series:
includes elements of sublevel 4d in the 5th period. Start with 39Y to 48Cd.
3rd transition series:
includes elements of sublevel 5d in the 6th period. Start with 57La to 80Hg.
f -block
are separated from the table so that the table is not too wide ( long )
lanthanides: placed in 6th period, in which 4f sublevel is filled successively.
They named wrongly as rare earths. G.R; because they are quite similar and
very difficult to be separated.
Actinides: placed in 7th period, in which 5f sublevel is filled successively.
They are radioactive elements and their nuclei are unstable
N.B
The f block elements are also called inner transition elements.
Question
What is the block of elements which includes the largest number of elements in the
sixth period in the periodic table ?
(a) s-block.
(b) p-block.
(c) d-block.
(d) f-block.
