Periodic Classification of elements (lect-2)

Periodic Classification of elements (lect-2)

Periodic Trends

• Periodicity in Properties:

  1. The electronic configuration of the atoms display periodic variations with increase in atomic number.

  2. The elements exhibit periodic variations of physical and chemical properties.

  Following are some the important properties of the elements:

  1. Valency

  2. Atomic size

  3. Metallic and non - metallic character

Trends in Modern Periodic table:

• 1.Valency:

  Valency is the number of electrons exchangeable by the element in a chemical reaction or the number of valence electrons present in the outermost shell of its atom. 

• Variation in a period: On moving from left to right in each short period, the valency of elements increases from 1 to 4 and then decreases to 0

• Variation in a group: Since, the number of valence electrons of all the elements in a group is same, all the elements in a group have same valency. 

Multiple Choice

The atoms of elements belonging to the same group of periodic table have same number of_____.

• protons

• electrons

• neutrons

• electrons in outermost

Multiple Choice

All the elements in a period in the periodic table have the same _______

• atomic number

• electronic configuration

• atomic weight

• valence shell

Multiple Choice

All the members in a group of a long form of periodic table have the same ________.

• valency

• number of valence electrons

• chemical properties

• All of the above

• 2. Atomic Size:

  The term atomic size refers to the radius of an atom & may be visualized as the distance between the center of the nucleus and the outermost shell of an isolated atom.

• Variation in a period:

  On moving from left to right in a period of the periodic table, the size of atoms decreases. 

• Variation in a group:

  On going down in a group of the periodic table, the size of atoms increases. 

Multiple Choice

Which has the maximum atomic radius ?

• Al

• Si

• P

• Mg

Multiple Choice

In modern periodic table, arrange the third row elements Na, Mg, Al and Si in the increasing order of their atomic size ______.

• Na > Mg > Al > Si

• Al > Si > Na > Mg

• Si > Al > Mg > Na

• Na > Al > Si > Mg

Multiple Choice

In the third period of the periodic table, the element having smallest size is _____.

• Na

• Ar

• Cl

• Si

• 3. Metallic and Non Metallic Properties:

  A. Metalloids

  i) A zig-zag line that separates metals from non-metals.

  ii) Exhibit some properties of both metals and non-metals

• B. Metallic properties

  i) Metals are characterized by their tendency to lose electrons while forming bond and hence, they are electropositive in nature.

  ii) Metals, generally possess 1 to 3 electrons in outermost shell.

  iii) Metals, are found on the left hand side of the periodic table.

  Variation in a period: On moving from left to right in a period, metallic character of elements decreases.

  Variation in a group: On going down in a group, the metallic character of elements increases.

• C. Non-Metallic Properties

  i) Non - metals are characterized by their tendency to gain electrons while forming bonds & hence they are electronegative.

  ii) They generally possess 4 to 8 electrons in outermost shell.

  iii) They are found on the right hand side of the Periodic Table.

  Variation in a period:

  On moving from left to right in a period, the non-metallic character of elements increases.

  Variation in a group:

  On going down in a group, non-metallic character of elements decreases.

• D. Nature of Oxides:

  Oxides of metals are basic and that of non-metals are acidic .

  Variation in a period:

  On moving from left to right in a period, as the metallic character of the elements decreases, the basic nature of oxides also decreases.

  On moving from left to right in a period, as the non-metallic character of elements increases, the acidic nature of oxides also increases.

  Variation in a group:

  On going down in a group, as the metallic character of elements increases, the basic nature of oxides also increases.

  On going down in a group, as non-metallic character of elements

  decreases, the acidic nature of oxides also decreases. 

Multiple Choice

In the periodic table, the metallic character of elements ______.

• decreases from left to right and down the group

• decreases from left to right and increases down the group

• increases from left to right and down the group

• increases from left to right and decreases down the group

Multiple Choice

From top to bottom in a group of the periodic table electropositive character of the element ______.

• increases

• decreases

• remains unchanged

• changes irregularly

Multiple Choice

Which of the following increases along the period ?

• Number of valence electrons

• Atomic size

• Electropositive character

• All of these

Multiple Choice

The total number of elements found in 4th period of modern periodic table is _____.

• 8

• 18

• 32

• 12

Multiple Choice

Which of the following element loses an electron most easily?

• Na

• Mg

• K

• Ca

Multiple Choice

For ⁵²X₂₄ , number of electrons is _______.

• 52

• 24

• 76

• 28

Multiple Choice

To complete the octate, outer most shell of Aluminium ______.

• looses two electrons

• gains three electrons

• looses three electrons

• shares four electrons

Multiple Choice

Each of the following element forms univalent ions except _____

• Li

• Na

• Mg

• K

Multiple Choice

The elements with atomic numbers 3, 11, 19, 37 and 55 are all termed as____.

• Noble metals

• Alkali metals

• Noble gases

• Alkaline Earth metals

Multiple Choice

Why are the elements lithium, sodium and potassium called alkali metals ?

• Because they reacts with water to form alkali

• Because they form acidic oxides

• Because they are present in first group

• Because they are less reactive in nature

Multiple Choice

Alkali metals in each period have ______.

• Smallest size

• Lowest I.E.

• Highest E.A

• Highest electronegativity

Multiple Choice

Which of the following statements is not a correct statement about the trends when going from left to right across the periods of the periodic table ?

• The elements become less metallic in nature

• The number of valence electrons increases

• The atoms lose their electrons more easily

• The oxides become more acidic

Multiple Choice

Considering the elements B, Al, Mg and K, the correct order of their metallic character is _____.

• B > Al > Mg > K

• AI > Mg > B > K

• Mg > Al > K > B

• K > Mg > Al > B

Multiple Choice

Which of the following elements has maximum metallic character ?

• Li

• N

• Na

• P

Multiple Choice

On moving left to right in a period, in the periodic table, metallic character _____.

• decrease

• increases

• remains same

• first increase, then decreases

Multiple Choice

On moving from top to bottom in a group, in the periodic table, size of an atom______.

• increases

• decreases

• remains same

• first increases, then decreases

Multiple Choice

On moving from top to bottom in a group, in the periodic table, valency ______.

• increase

• decreases

• remains same

• first increases, then decreases