Question

few points about modern periodic table​

Answer 1

The modern periodic law states that the physical and chemical properties of the elements are the periodic functions of their atomic numbers.

Scientists arranged elements in increasing order of their atomic numbers from left to right across each row. And discovered that the elements having similar properties repeat after regular intervals.

Why atomic number and not atomic mass?

Atomic mass is the total mass of the protons andneutrons present in a nucleus of an atom. Whereas, the atomic number is the number of protons in a nucleus. Also, the number of protons in the nucleus is equal to the electrons present outside the nucleus.

We know that the nucleus is deep-seated inside an atom. But the electrons outside it, especially the ones in the outermost shell, are free to move around. Hence they take part in chemical reactions. For this reason, the properties of an element depend on the atomic number rather than the atomic mass.

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Answer 2

Answer:

The modern periodic table of the elements contains 18 groups, or vertical columns. Elements in a group have similar chemical and physical properties because they have the same number of outer electrons. Elements in a group are like members of a family--each is different, but all are related by common characteristics.

The main features of modern periodic table

The long form of periodic table consist of vertical columns called groups and horizontal rows called periods.

• Elements are arranged in the increasing order of atomic numbers.
• Elements in the modern periodic table are arranged in 7 periods and 18 groups.
• Horizontal rows are called periods and vertical columns are called groups.
• Elements are placed in periods based on the number of shells in their atoms.
• The shortest period is the first period which contains only two elements – Hydrogen and Helium.
• The second period contains elements from Lithium to Neon.
• The third period contains elements from Sodium to Argon.
• The fourth period contains elements from Potassium to Krypton.
• The fifth period contains elements from Rubidium to Xenon.
• Sixth period is considered as the longest periods in the periodic table. It contains elements from Cesium to Radon
• Seventh period is incomplete period
• In group IIIB of the sixth period Lanthanides are placed.
• In group IIIB of the seventh period Actinides are placed
• In periodic table Lanthanides and Actinides are shown in the bottom of the periodic table.

Explanation:

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