Periodic Properties and Variations – Notes
Modern Periodic Table
Atomic number is the number of protons in an atom.
The number of electrons in an atom is equal to the number of protons.
An atom is electrically neutral.
Valence electrons: Electrons in the outermost shell of an atom.
Electronic configuration: The arrangement of electrons in an atom around its nucleus.
Bohr’s theory: Electrons are not located randomly around an atom’s nucleus, but occur in definite electrons shells.
The physical and chemical properties of elements are a periodic function of their atomic numbers.
Elements are arranged in the increasing order of atomic number.
The modern periodic table consists of:
- 7 horizontal periods
- 18 vertical groups
The properties of the elements in the periodic table change gradually from left to right.