Question

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Explain the tends in the Modern periodic table.

Class - 10th
Chapter - Periodic classification of elements.

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Answer 1

Corrected Question :

⇒ Explain the trends in the modern periodic table.

$\huge\bf{Answer :}$

⇒ The arrangements of elements were on the basis of their Electronic Configuration.

⇒ Horizontal rows which are placed in the table is known as Periods.

1. 1st Period - 2 elements ( very short period )
2. 2nd Period - 8 elements ( short period )
3. 3rd Period - 8 elements ( short period )
4. 4th Period - 18 elements ( long period )
5. 5th Period - 18 elements ( long period )
6. 6th Period - 32 elements ( very long period )
7. 7th Periods - Rest of the elements ( incomplete period )

⇒ Period number of elements depends upon the number of shells in it's electronic configuration.

✣Valence electrons :

On moving from Left hand side to Right hand side across the modern periodic table, the number of valence electrons increases.

Reason : From left hand side to right hand side, atomic number of an element increases because of addition of elements in it's outermost ( or valence ) shell. Therefore, valence electrons increases from one to eight.

✣Valency :

On moving from left hand side to right hand side across the table, valency first increases from 1 to 4, and then gradually decreases from 4 to zero.

Reasons :-

• Elements having valence electrons 1,2 and 3 lose their electrons and their valency becomes equal to the number of electrons.
• Elements having valence electrons 5,6 and 7 have the capability to gain electrons and their valency can be calculated by the formula, e = 8 - valence electrons, where e = valency.
• Elements having the valency 4, forms covalent compounds and has the valency 4 along with 4 valence electrons.

✣Size of atom :

On moving from Left hand side to right hand side of the table, the atomic number of the element increases.

Reasons : Electrons are added to the valence shell, on the other hand, protons are added in the nucleus of the atom. Since, protons are present in the high concentration area of nucleus, the positive charged protons are dominant in that area over the charge by electrons.

Thus, positive charged electrons attracts the negative charged ones to the nucleus of the atoms. This process leads to the contraction and shortening of atomic radius.

Hence, the atomic radius decreases gradually.

Answer 2

ᴘᴇʀɪᴏᴅɪᴄ ᴛʀᴇɴᴅꜱ ᴀʀᴇ ꜱᴘᴇᴄɪꜰɪᴄ ᴘᴀᴛᴛᴇʀɴꜱ ɪɴ ᴛʜᴇ ᴘʀᴏᴘᴇʀᴛɪᴇꜱ ᴏꜰ ᴄʜᴇᴍɪᴄᴀʟ ᴇʟᴇᴍᴇɴᴛꜱ ᴛʜᴀᴛ ᴀʀᴇ ʀᴇᴠᴇᴀʟᴇᴅ ɪɴ ᴛʜᴇ ᴘᴇʀɪᴏᴅɪᴄ ᴛᴀʙʟᴇ ᴏꜰ ᴇʟᴇᴍᴇɴᴛꜱ. ᴍᴀᴊᴏʀ ᴘᴇʀɪᴏᴅɪᴄ ᴛʀᴇɴᴅꜱ ɪɴᴄʟᴜᴅᴇ ᴇʟᴇᴄᴛʀᴏɴᴇɢᴀᴛɪᴠɪᴛʏ, ɪᴏɴɪᴢᴀᴛɪᴏɴ ᴇɴᴇʀɢʏ, ᴇʟᴇᴄᴛʀᴏɴ ᴀꜰꜰɪɴɪᴛʏ, ᴀᴛᴏᴍɪᴄ ʀᴀᴅɪɪ, ɪᴏɴɪᴄ ʀᴀᴅɪᴜꜱ, ᴍᴇᴛᴀʟʟɪᴄ ᴄʜᴀʀᴀᴄᴛᴇʀ, ᴀɴᴅ ᴄʜᴇᴍɪᴄᴀʟ ʀᴇᴀᴄᴛɪᴠɪᴛʏ.

ᴛʜᴇ ᴘᴇʀɪᴏᴅɪᴄ ᴛʀᴇɴᴅꜱ ɪɴ ᴘʀᴏᴘᴇʀᴛɪᴇꜱ ᴏꜰ ᴇʟᴇᴍᴇɴᴛꜱ

ᴘᴇʀɪᴏᴅɪᴄ ᴛʀᴇɴᴅꜱ ᴀʀɪꜱᴇ ꜰʀᴏᴍ ᴛʜᴇ ᴄʜᴀɴɢᴇꜱ ɪɴ ᴛʜᴇ ᴀᴛᴏᴍɪᴄ ꜱᴛʀᴜᴄᴛᴜʀᴇ ᴏꜰ ᴛʜᴇ ᴄʜᴇᴍɪᴄᴀʟ ᴇʟᴇᴍᴇɴᴛꜱ ᴡɪᴛʜɪɴ ᴛʜᴇɪʀ ʀᴇꜱᴘᴇᴄᴛɪᴠᴇ ᴘᴇʀɪᴏᴅꜱ (ʜᴏʀɪᴢᴏɴᴛᴀʟ ʀᴏᴡꜱ) ᴀɴᴅ ɢʀᴏᴜᴘꜱ ɪɴ ᴛʜᴇ ᴘᴇʀɪᴏᴅɪᴄ ᴛᴀʙʟᴇ. ᴛʜᴇꜱᴇ ʟᴀᴡꜱ ᴇɴᴀʙʟᴇ ᴛʜᴇ ᴄʜᴇᴍɪᴄᴀʟ ᴇʟᴇᴍᴇɴᴛꜱ ᴛᴏ ʙᴇ ᴏʀɢᴀɴɪᴢᴇᴅ ɪɴ ᴛʜᴇ ᴘᴇʀɪᴏᴅɪᴄ ᴛᴀʙʟᴇ ʙᴀꜱᴇᴅ ᴏɴ ᴛʜᴇɪʀ ᴀᴛᴏᴍɪᴄ ꜱᴛʀᴜᴄᴛᴜʀᴇꜱ ᴀɴᴅ ᴘʀᴏᴘᴇʀᴛɪᴇꜱ. ᴅᴜᴇ ᴛᴏ ᴛʜᴇ ᴘᴇʀɪᴏᴅɪᴄ ᴛʀᴇɴᴅꜱ, ᴛʜᴇ ᴜɴᴋɴᴏᴡɴ ᴘʀᴏᴘᴇʀᴛɪᴇꜱ ᴏꜰ ᴀɴʏ ᴇʟᴇᴍᴇɴᴛ ᴄᴀɴ ʙᴇ ᴘᴀʀᴛɪᴀʟʟʏ ᴋɴᴏᴡɴ.

ꜱᴇᴠᴇʀᴀʟ ᴇxᴄᴇᴘᴛɪᴏɴꜱ, ʜᴏᴡᴇᴠᴇʀ, ᴅᴏ ᴇxɪꜱᴛ, ꜱᴜᴄʜ ᴀꜱ ᴛʜᴀᴛ ᴏꜰ ɪᴏɴɪᴢᴀᴛɪᴏɴ ᴇɴᴇʀɢʏ ɪɴ ɢʀᴏᴜᴘ 3, ᴛʜᴇ ᴇʟᴇᴄᴛʀᴏɴ ᴀꜰꜰɪɴɪᴛʏ ᴛʀᴇɴᴅ ᴏꜰ ɢʀᴏᴜᴘ 17, ᴛʜᴇ ᴅᴇɴꜱɪᴛʏ ᴛʀᴇɴᴅ ᴏꜰ ᴀʟᴋᴀʟɪ ᴍᴇᴛᴀʟꜱ ᴀᴋᴀ ɢʀᴏᴜᴘ 1 ᴇʟᴇᴍᴇɴᴛꜱ ᴀɴᴅ ꜱᴏ ᴏɴ.

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