Note on Reactivity of Metals and Non- Metals

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Reactivity of Metals

The elements which belong to Group IA, IIA and IIA are metals. The reactivity of an element belonging to metals increase on moving from top to bottom in a group of the periodic table.

While moving from top to bottom in a group of metals in the periodic table, the atomic size increases with the increment in the number of shells and the force of attraction between the nucleus and valence shell decrease. This is the reason why the bigger atom/s can lose the valence electron/s more easily than the smaller atom/s.  This is the reason why the bigger atom/s can lose the valence electron/s more easily than the smaller atom/s. Thus, the tendency of losing the valence electron/s increases and their chemical reactivity increases on moving from top to bottom in a group of metals.

Period

Group IA

Atomic Size

Reactivity

2

Lithium (Li)

2, 1 (Smallest)

↓  Reactivity increases from top to bottom

3

Sodium (Na)

2, 8, 1 (Medium)

4

Potassium (K)

2, 8, 8, 1 (Biggest)

 

Why is potassium highly reactive than the sodium?

As sodium and potassium both are alkali metals that belong to Group IA of the periodic table. They have one valence electron in their valence shell. As we move from top to bottom, the reactivity of metallic elements of Group IA increases. Since the atomic size of sodium is smaller than the atomic size of potassium, sodium has more force of attraction between the nucleus and valence shell than that of potassium. As a result, potassium loses its valence electron more easily than sodium. In conclusion, potassium is highly reactive than the sodium.

Reactivity of Non- Metals

The elements which belong to Group VA, VIA, and VIIA are non- metals. While moving from top to bottom in a group of the periodic table, the reactivity of non- metals decreases.

While moving from top to bottom in a group of non- metals, the atomic size increases with the additional number of shells and the force of attraction between the nucleus and valence shell decreases. The smaller atom/s can gain the valence electron/s more easily than the bigger atom/s as the force of attraction between the nucleus and valence electrons of smaller atom/s is more than that of the bigger atoms. Thus, the tendency of gaining electron/s in the valence shell decreases as well as the chemical reactivity also decreases on moving from top to bottom in a group of non- metals.

Period

Group VIIA

Atomic Size

Reactivity

2

Fluorine (F)

2, 7 (Smallest)

↓         Reactivity decreases from top to bottom

3

Chlorine (Cl)

2, 8, 7 (Medium)

4

Bromine (Br)

2, 8, 18, 7 (Biggest)

 

Why is fluorine more reactive than chlorine?

As fluorine and chlorine, both are non- metals which belong to Group VIIA of the periodic table. The reactivity of the non- metallic elements that belong to Group VIIA decreases as we move from top to bottom. Since the atomic size of fluorine is smaller than that of chlorine, the force of attraction between the nucleus and valence electrons of the valence shell is more in fluorine, so it can easily gain one electron than chlorine. In conclusion, fluorine is more reactive than chlorine.

Sub- Shells (Orbital)

The atom, which has two electrons in its valence shell, i.e. only one orbit is said to be duplet. For e.g.: helium. The atoms, which have eight elements in its valence shell, is said to be octet. For e.g.: argon, neon, krypton, etc.

Since, the electronic configuration based on 2n­­­2 is not sufficient to explain all the electronic configuration of all elements, the concept of subshell was introduced. Orbital or subshell is the region around the nucleus there is a maximum probability of finding electrons. The concept of subshell explains that each shell consists of a number of subshells that gives more detail description about the electronic configuration of all the elements. Subshells are denoted by the letters s, p, d, and f.

Main Shell

Sub- shells

K- shell (n = 1)

s

L- shell (n = 2)

s and p

M- shell (n = 3)

s, p and d

N- shell (n = 4)

s, p, d and f

O- shell (n = 5)

s, p, d and f

P- shell (n = 6)

s, p and d

Q- shell (n = 7)

s and p

 

The maximum number of elements in each shell is shown below:

Subshell

Maximum no. of Elements

s

2

p

6

d

10

f

14

 

 

 

The relation between 2n2 rule and sub- shells can be presented as follows:

Main Shell

Sub Shell

Total Electrons

K (n = 1)

1s

2

L (n = 2)

2s, 2p

2 + 6 = 8

M (n = 3)

3s, 3p, 3d

2 + 6 + 10 = 18

N (n = 4)

4s, 4p, 4d, 4f

2 + 6 + 10 + 14 = 32

 

Blocks of Elements in Modern Periodic Table

The arrangement of the electrons in the subshells describes the physical and chemical properties of the elements. On the basis of the arrangement of electrons in the subshell, the elements in the periodic table are divided into 4 blocks: s- block, p- block, d- block and f- block.

s- Block

The elements of groups IA (alkali metals) and IIA (alkali earth metals) are included in the s- block. They are 12 in number which lies on the left side of the periodic table. The s- block is filled by one or two valence electrons. They form positive ions by losing one or two electrons during their combination with other elements. The elements Li, Na, K, Be, etc. are the elements of s- block.

p- Block

All the metals, metalloids, non- metals and inert gases which are present in Group IIIA, IVA, VA, VIA, VIIA and group 0 are included in p- block. They are 31 in number that lies on the right side of the modern periodic table. The elements of this block have 3, 4, 5, 6, 7 and 8 valence electrons which are filled in the p- orbital of all the elements of Group IIIA and VIIA. The elements of Group 0 which have completely filled p- orbital (ns2, np6) are called noble gases. C, N, O, F, Cl, etc. are some of the s- block elements.

d- Block

All the metallic elements of subgroup IIIB, IVB, VB, VIB, VIIB, VIII, IB and IIB belong to d- block. The elements of d- block are said to be transitional elements as they lie between s- block and p- block elements in the middle of the periodic table. Ag, Au, Fe, Cu, etc. are the examples of d- block elements.

f- Block

All the elements belonging to lanthanide and actinide series are f- block elements which are also known as inner- transition elements as it is a transit to move from the transition elements of Group IIIB to Group IVB. They are 28 in number. The chemical properties of both series are similar and they are placed in two rows at the bottom of the periodic table. The elements in f- block are incomplete and are gradually filled as the increase in the atomic number.

The number of elements placed in each period having s, p, d, and f- block are tabulated below:

Periods in Table

No. of Elements in Blocks

s

p

d

f

1

2

-

-

-

2

2

6

-

-

3

2

6

-

-

4

2

6

10

-

5

2

6

10

-

6

2

6

10

14

7

2

6

10

14

  1. Valency and atomic size determine the reactivity of elements. The elements of lower valency are more reactive than those which have more valency. Metals with a big atomic size and non- metals with a small atomic size are more active than others.
  2. In a group, the reactivity of metals increases from top to bottom and that of non- metals decreases from top to bottom.
  3. The atom having two electrons in its valence shell is known as duplet.
  4. The atoms having eight elements in its valence shell is known as octet.
  5. The elements of d- block are said to transitional elements.
  6. The elements of f- block are said to be inner- transitional elements.
.

Very Short Questions

The group IA, IIA and IIIA contains metals which are electropositive in nature. They lose valence electrons easily from top to bottom in the group due to their increasing atomic size.

In group VA, VIA and VIIA reactivity of elements decreases from top to bottom because they contain non- metals which are electronegative and the tendency to gain the electrons decreases from top to bottom due to the increment in their atomic size. 

S. No. s- block S. No. p- block
1. The s- block elements have s- sub-shell as the last orbital. 1. The p- block elements have p- sub-shell as the last orbital.
2. They have only 1 or 2 electrons in the last sub- shells. 2. They have 1 to 6 electrons in the last sub- shells.
3. The chemical reactivity of elements increases while going downwards in a group. 3. The chemical reactivity of elements decreases while going downwards in a group.
4. The melting point and boiling point decreases while going downward in a group. 4.  The melting and boiling point increases while going downward in a group.

As sodium and potassium both are alkali metals that belong to Group IA of the periodic table. They have one valence electron in their valence shell. As we move from top to bottom, the reactivity of metallic elements of Group IA increases. Since the atomic size of sodium is smaller than the atomic size of potassium, sodium has more force of attraction between the nucleus and valence shell than that of potassium. As a result, potassium loses its valence electron more easily than sodium. In conclusion, potassium is highly reactive than sodium.

As fluorine and chlorine, both are non- metals which belong to Group VIIA of the periodic table. The reactivity of the non- metallic elements that belong to Group VIIA decreases as we move from top to bottom. Since the atomic size of fluorine is smaller than that of chlorine, the force of attraction between the nucleus and valence electrons of the valence shell is more in fluorine, so it can easily gain one electron than chlorine. In conclusion, fluorine is more reactive than chlorine.

0%
  • The elements of group IA, IIA and IIIA are ______.

    metalloids
    all of them
    none of them
    metals
    inert gases
    non- metals
  • The reactivity of non- metals ______ on moving from top to bottom in a group.

    decreases
    non of them
    remain constant
    doubles
    all of them
    increases
  • The d- sub shell has maximum ______ electrons.

    two
    fourteen
    six
    ten
    eight
    one
  • The d- block elements are also known as ______.

    alkalis
    metals
    metalloids
    transitional elements
    inert gases
    non- metals
  • The elements in a periodic table is divided into ______ blocks.

    eight
    two
    fourteen
    sixteen
    ten
    four
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