Classification of elements and periodicity in properties important points

Classification of elements and periodicity in properties important points: The classification of elements and periodicity in properties is the arrangement of the chemical elements into groups based on their similar properties and their increasing order of atomic numbers. The modern periodic table organizes the elements into rows and columns according to their electronic configurations and chemical properties.

Elements are classified into three main categories: metals, nonmetals, and the metalloids. Metals are typically shiny, malleable, ductile, and good the conductors of heat and electricity. Nonmetals are typically dull, brittle, and the poor conductors of heat and electricity. Metalloids have the properties that are intermediate between the metals and nonmetals. The elements in the periodic table is arranged in periods (horizontal rows) and groups (vertical columns). The number of electrons in outermost shell, or valence electrons, determines the element’s chemical properties. The elements in a group have the similar properties due to their similar electronic configurations.

The periodic table also has several trends in their properties. Atomic radius of the elements generally decreases from left to right across a period and increases from top to bottom within a group. Ionization energy of the elements generally increases from left to right across a period and decreases from top to bottom within a group. Electronegativity of the elements generally increases from left to right across a period and decreases from top to bottom within a group.

Classification of elements and periodicity in properties important points, Classification of elements and periodicity in properties important points, Classification of elements and periodicity in properties important points, Classification of elements and periodicity in properties important points

NCERT Chemistry Class 11 Chapter 3 – Classification of elements and periodicity 25 Important Points

There are 25 important points on Classification of elements and periodicity in properties:

1. The modern periodic table is based on electronic configuration of elements.
2. The periodic table is arranged in increasing order of their atomic number.
3. The elements in periodic table are arranged in periods and groups.
4. A period is the horizontal row in the periodic table.
5. A group is the vertical column in the periodic table.
6. The modern periodic table have 18 groups and 7 periods.
7. The elements in a group have the similar chemical and physical properties.
8. The elements of a period have different chemical and physical properties.
9. The electronic configuration of the elements determines their properties.
10. Valence shell of an element determines its chemical properties.
11. The valence electrons of an element are electrons in the outermost shell.
12. The valency of an element is defined as the number of electrons it can lose, gain or share to attain a stable configuration.
13. Metals are located on left side of the periodic table and nonmetals on the right.
14. Metalloids (or semimetals) are located along the diagonal line separating the metals and nonmetals.
15. The metals are the good conductors of heat and electricity, and are ductile and malleable.
16. The nonmetals are the poor conductors of heat and electricity, and are generally not ductile or malleable.
17. The metalloids have properties that are intermediate between metals and nonmetals.
18. The atomic radius (or size) of an element decreases from left to right across a period and increases down a group.
19. The ionization energy (or ionization potential) of an element increases from left to right across a period and decreases down a group.
20. The electron affinity of an element is defined as the energy released when an electron is added to a neutral atom. It generally increases from left to right across a period and decreases down a group.
21. The electronegativity of an element is defined as its ability to attract electrons towards itself in a chemical bond. It generally increases from left to right across a period and decreases down a group.
22. The metallic character of an element decreases from left to right across the period and increases down the group.
23. The reactivity of the metals generally increases down a group and decreases across a period from left to right.

24. The reactivity of the nonmetals generally decreases down a group and increases across a period from left to right.
25. Noble gases are the most stable elements and have very low reactivity. They have complete valence shells and do not readily form chemical bonds with the other elements.

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