ICSE class 10 Chemistry Hand Made Notes

Periodic Table notes for ICSE Class 10 Chemistry


1. History of the Periodic Table

• Dobereiner's Triads (1817):

o Grouped elements in sets of three based on similar
properties.

o The atomic mass of the middle element was
approximately the average of the other two.

o Example: Lithium (7), Sodium (23), Potassium (39).

• Newlands' Law of Octaves (1865):

o Arranged elements in increasing order of atomic masses.

o Every eighth element showed similar properties, like the
notes in music.

o Limitations:

▪ Worked only for elements up to Calcium.

▪ Did not leave space for undiscovered elements.

• Mendeleev's Periodic Table (1869):

o Arranged elements in increasing atomic masses.

o Left gaps for undiscovered elements, predicting their
properties.

o Grouped elements with similar properties together.

o Limitations:

▪ Could not explain isotopes.

▪ Some elements were placed out of order to fit into
groups.

• Modern Periodic Table (1913, Henry Moseley):

, o Based on atomic numbers (not masses).

o Resolved issues with Mendeleev’s arrangement.



2. Features of the Modern Periodic Table

• Structure:

o Groups: 18 vertical columns.

o Periods: 7 horizontal rows.

• Arrangement:

o Elements are arranged in increasing order of atomic
numbers.

o Elements in the same group have similar chemical
properties.

o Elements in the same period have the same number of
shells.



3. Periods and Their Characteristics

Periods:

1. Period 1 (Very Short Period):

o Contains 2 elements: Hydrogen (H) and Helium (He).

o Single shell (K-shell).

2. Period 2 (Short Period):

o Contains 8 elements: Lithium (Li) to Neon (Ne).

o Two shells (K and L).

3. Period 3 (Short Period):

o Contains 8 elements: Sodium (Na) to Argon (Ar).

o Three shells (K, L, and M).