Periodic Table

Question 1

What is the Modern periodic law?

Answer 1

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

Question 2

What determines the position of an element in the periodic table?

Answer 2

The position of an element is determined by its atomic number and its electron configuration.

Question 3

Which element is the most abundant in the Earth’s crust?

Answer 3

Oxygen is the most abundant element in the Earth’s crust.

Question 4

What is the general trend in atomic radius as you move from left to right across a period?

Answer 4

The atomic radius generally decreases as you move from left to right across a period.

Question 5

How does the reactivity of alkali metals change as you move down the group?

Answer 5

The reactivity of alkali metals increases as you move down the group.

Question 6

What is atomic radius?

Answer 6

The distance from the center of nucleus of an atom to outermost shell of electrons.

Question 7

What is covalent radius?

Answer 7

Half of the internuclear distance (bond length) between two like atoms bonded by single covalent bond.

Single Covalent Bond & Like atoms

Question 8

What is Van der Waal’s radius?

Answer 8

Half of the distance between nuclei of two non bonded neighboring atoms held by van der Waals force of attraction.

Non Bonded & Adjacent Molecules

Question 9

Which radius Van der Waal’s radius or covalent radius greater?

Answer 9

Van der Waal’s radius

Question 10

What is metallic radius?

Answer 10

It is defined as the half of the distance between nuclei of two adjacent atoms in close-packed crystal lattice.

Question 11

Which has a larger radius? H or He

Answer 11

He

Van der Waal’s radius > Covalent radius

Question 12

Which group element has the biggest radius along a period?

Answer 12

Noble elements (Group 18)

Question 13

Order of ionic radius of atom, cation and anion

Answer 13

Anion > Atom > Cation
(Shielding effect: Anion>Cation)

Anion : E Nuclear Charge decreases
Cation : E Nuclear Charge increases

Question 14

What is ionic radius?

Answer 14

The distance between the center of the nucleus and a point up to which the nucleus has its influence in an ion is ionic radius.

Question 15

What is the formula for Iso-electronic species?

Answer 15

Size is inversely proportional to atomic number
Size ∝ 1/Z

Question 16

Why is cation smaller in size than its parent atom?

Answer 16

When an electron is lost, electron-electron repulsion (and therefore, shielding) decreases and the protons are better able to pull the remaining electrons towards the nucleus and effective nuclear charge increases. Also when it loses a shell.

Question 17

Anion is larger in size than parent atom. Why? Explain

Answer 17

An additional electron occupies an outer orbital, there is increased electron-electron repulsion (and hence, increased shielding) which pushes the electrons further apart.

The electrons now outnumber the protons in the ion, the protons can not pull the extra electrons as tightly toward the nucleus; this results in decreased effective nuclear charge.

Question 18

Why do atomic radii decreases across the period? Explain

Answer 18

The atomic radius decreases because the effective nuclear charge increases as the number of protons in the nucleus increases. The shielding effect remains relatively constant since the additional electrons are added to the same energy level. As a result, the valence electrons are pulled closer to the nucleus, leading to a smaller atomic radius.

Question 19

Why do atomic radii increase down the group in periodic table?

Answer 19

Addition of Electron Shells, Increased Shielding, Reduced Effective Nuclear Charge

Question 20

What are acid and basic radicals?

Answer 20

Acid radicals are derived from acids and carry a negative charge, while basic radicals are derived from bases and carry a positive charge.

Question 21

Dobereiner’s Triad

Answer 21

• Elements having similar properties can be arranged in group of 3 called triad
  -Lithium, Sodium Potassium
  -Chlorine, Bromine and Iodine
• Atomic mass of Na = (Li + K) / 2

Question 22

Newland’s law of octaves

Answer 22

-Repetition of similar character when arranged in increasing order of atomic weights.

Question 23

Lother Mayer’s atomic volume curve

Answer 23

• X axis : Atomic weight
• Y axis : Atomic Volume
• Elements having similar properties occupy similar positions in the curve.

Question 24

How many groups and periods were there in Mendeleev’s periodic table?

Answer 24

Group - 9
Period - 7

Question 25

What were the anomalies in Mendeleev’s periodic table?

Answer 25

1. Position of Hydrogen is not clear
2. Position of Isotopes : no separate positions which should’ve been given according to Mendeleev’s periodic law
3. Inversion of Law : Some elements having higher atomic mass were placed before elements with lower atomic mass
4. Separation of similar elements and grouping of dissimilar elements.
5. No explanation for the cause of periodicity

Question 26

Why is Modern Periodic table superior to Mendeleev’s periodic table?

Answer 26

1. Eliminated many defects of Mendeleev’s Periodic table
2. It explains the cause of periodicity in properties of elements

Question 27

How is periodicity explained in modern periodic table?

Answer 27

It explains as
- Atomic number is equal to the number of protons of an atom of an element. Properties of an element are governed by its electronic configuration, When elements are arranged in increasing order of their atomic numbers, their electronic configuration gradually changes hence properties change gradually. After regular intervals, elements having similar outer electronic configuration reappear and properties are repeated.

Question 28

What are s-block elements?

Answer 28

The elements whose outermost electron enters the s orbital of ultimate shell are s-block elements.

Question 29

What are p-block elements?

Answer 29

The elements whose outermost electron enters p orbital of ultimate shell are p-block elements,

Question 30

What are d-block elements?

Answer 30

The elements whose outermost electron enters d orbital of penultimate shell are p-block elements.

Question 31

What are f-block elements?

Answer 31

The elements whose outermost electron enters d orbital of antepenultimate shell are p-block elements.

Question 32

Why are d-block elements called transitional elements?

Answer 32

• Because of transitional position and transitional properties between s-block and p-block elements.

Question 33

Electronic configuration of elements from 21 - 25 :

Answer 33

21. Scandium (Sc) – Atomic number 21:
    1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s²
22. Titanium (Ti) – Atomic number 22:
    1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s²
23. Vanadium (V) – Atomic number 23:
    1s² 2s² 2p⁶ 3s² 3p⁶ 3d³ 4s²
24. Chromium (Cr) – Atomic number 24:
    1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹ ( Exception)
25. Manganese (Mn) – Atomic number 25:
    1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s²

Question 34

Electronic configuration of elements from 26 - 30 :

Answer 34

26. Iron (Fe) – Atomic number 26:
    1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²
27. Cobalt (Co) – Atomic number 27:
    1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷ 4s²
28. Nickel (Ni) – Atomic number 28:
    1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁸ 4s²
29. Copper (Cu) – Atomic number 29:
    1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹ ( Exception )
30. Zinc (Zn) – Atomic number 30:
    1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s²

Question 35

What is diagonal relationship?

Answer 35

Some elements of period 2 show similarity in properties with elements of period 3 lying diagonally below the respective elements.
For re: Li shows diagonal relationship with magnesium. Properties like BP,IE are similar due to similarity in atomic radius, electronegativity and charge density.

Question 36

What are bridge elements?

Answer 36

Elements of 3rd period are called bridge elements. Na, Ma