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1. Na, Mg, P, Cl 

2. Li, C, N, F 

3. Na, Al, S, Cl 

4. F, O, C, Li 

5. He, Ne, Ar

1. Li < Na < K < Rb < Cs 

2. Na > Mg > Si > S > Cl 

3. K < Na < Si < S < Cl . 

4. I < Br < F < Cl

1. He, ne, Ar (increasing number of electron shells) 

2. K, Na, Li (increasing ionisation energy) 

3. Br, Cl, F (increasing electronegativity) 

4. Li, Na, K (increasing atomic size)

If three shells → element belongs to third period. 

If three valence electrons → element belongs to 13 group.

(1) Electro negativity 

(2) Valence electrons

(a) Since it belongs to period 3 it has 3 shells, K, L and M. The outermost M shell will have 2 valence electrons as it is placed in group II

(b) With 2 valence electrons, its valency will be 2.

(c) Since it has electronic configuration of 2, 8, 2, its atomic number is 12 and hence X is Magnesium

(d) It is a metal.

(i) Though the number of shells remain the same, number of valence electrons increases by one, as we move across any given period  from left to right.

(ii) While going from top to bottom in a group, the number of shells increases successively i.e. one by one but the number of valence electrons remains the same.

(i) Elements in the same group have equal valency.

(ii) Valency depends upon the number of valence electrons in an atom.

(iii) Copper and zinc are transition elements.

(iv) Noble gases are placed at the extreme right of the periodic table.

Noble gases are unreactive since they have their outermost orbit complete. Due to stable electronic configuration they hardly react with other elements. So these elements are placed in a separate group i.e.18

(a) Since the elements in a group have same number of valence electrons, they can either contain metals or non-metals like alkali and alkaline metals have only metals whereas halogens are non-metals.

(b) No two elements have the same number of electrons instead atoms of the same elements in the same group have the same number of valence electrons.

(c) Non-metals have the tendency to gain electrons to attain stable configuration and therefore are said to be electronegative. As we move from left to right the increase in atomic number and decrease in size results in a greater nuclear pull. As a result the non-metallic character increases across a period.

(d) On moving from left to right in a period, the reactivity first decreases and then increases since the tendency to lose electrons first decreases on going from left to right and then from P to Cl, tendency to gain electrons increases, so reactivity increases then. In case of a group, reactivity increases on going down since the tendency to lose electrons increases but for non-metals, reactivity decreases on going down the group as the tendency to gain electrons decreases down the group.

The name of 17th group’s elements is halogens.

The IUPAC name for atomic number 120 is Unbinilium and symbol is Ubn.

The lanthanides are f-block elements which contain seven f-orbitals. The maximum electrons can be filled in f-orbitals are 14. Hence, lanthanides have total 14 elements.

Lanthanum, cerium, lutetium.

• In solid-state - sodium, aluminum, carbon 
• In liquid state – Bromine 
• In gaseous state – oxygen, neon, argon

The amount of energy released when an atom in the gaseous state accepts an electron to form an anion → Electron Affinity. 

1. M and O combine with electrovalent bond. 

2. One 

3. Group I

(b) Nitrogen (N), between carbon and oxygen

(c) Carbon

(d) Be< N< F

(e) Fluorine

Electronegativity measures an atom's tendency to attract shared pair of electrons towards itself.

Its S.I unit is Pauling unit.

As the size of atom increases ionization energy decreases.

A metal (2) An element with electronic configuration 2, 8, 8,3 

B iron (1) The metal that forms two types of ions 

i. Sodium atom

ii. Chlorine atom

Newland arranged the element only upto calcium. After calcium every eighth element did not possess properties similar to that of the first. In order to fit the existing elements Newland placed two elements in the same position which differed in the properties. 

i. E 

ii. C 

iii. D 

iv. A 

Since size of chlorine is bigger than fluorine hence the electrons being farther away from the nucleus experience a lesser force of attraction, hence electron negativity of chlorine is less than fluorine

i. Potassium (K)

ii. Hydrogen [H]

iii. Increases

iv. Number of shells increases. 

As we move from top to bottom of a group in the periodic table the size of the atom increases as there is an increase in the number of shells.

(a) Element with atomic number 9 and 35

(b) Element with atomic number 9.

1. No.

2. On moving from left to right in a period, as nuclear charge increases, the force of attraction on the outer-most electrons increases and consequently the size of atom decreases.

Cerium with atomic No. 58

(i) Yes, these elements belong to the same group but are not from the same period.

(ii) We know that m.p. decreases on going down the group. Hence, from the above table, the elements can be ordered according to their period as follows:

The metallic character increases as one moves down the group. Hence, the order of the given elements with increasing metallic character is as follows: B

(a) SOL: Na and F

(b) SOL: Argon

(c) SOL: C, N, O and F are non-metals present in period 2 while Na, Mg and Al are metals in period 3.

(d) SOL: Silicon

(e) SOL: Argon

(f) SOL: Mg

(g) SOL: Fluorine

(h) SOL: K

Periodicity is observed due to the similar electronic configuration.

(Number of valence electrons / atomic number / electronic configuration).

Combining capacity of an element is known as Valency.

Elements exhibiting the properties of both metal as well as nonmetal are called metalloids, eg. Silicon [Si], germanium [Ge] Arsenic [As], Antimony [Sb] and Tellurium [Te] belongs to this category.

(a) Ionization energy increases as we move from left to right across a period as the atomic size decreases.

(b) Ionization energy decreases down a group as the atomic size increases.

a) P and S, Q and R – belongs to same period 

b) P and Q, belongs to same group 

c) S 

d) R belongs to 3rd period and 15^th group

Transition elements because last two shells of these elements namely outermost and penultimate shells are incomplete.

a) B, D, and A, C because the number of shells are same. 

b) A, D because the number of electrons in the outermost shell is same. 

c) ‘C’ belongs to second period and 17^th group

Al has strongest metallic character. 

1.

The atom of the elements of these group show the periodically in electron filling they contain 1 -8 electron in their outermost shell. The elements of these groups are called representative elements.

2. Helium, Neon, Argon, Krypton, Xenon, Radon

3. ₂He – 2 

₁₀Ne – 2, 8 

₁₈Ar – 2, 8, 8 

₃₆Kr – 2, 8, 18, 8 

₅₄Xe – 2, 8, 18, 18, 8 

₈₆Rn – 2, 8, 18, 32, 18, 8

4. 8

5. They have a stable configuration in the outermost shell.

6. Elements of group 3-12 in the periodic table are transition elements

7. Copper, silver, gold, iron

8. Yes

An element A with atomic number 14 belongs to period three and there are eight elements in this period.

(i) Electronic configuration of P: 2, 8, 5

(ii) 15th Group and 3rd Period.

(iii)Valency of P = 8 - 5 = 3

(iv)Phosphorus is a non-metal.

(v) It is an oxidizing agent.

(vi)Formula with chlorine = PCl3

In the periodic table, while moving from to top to bottom in groups metallic character generally increases while non-metallic character decreases. In a period as we move form left to right metallic character generally decreases while non-metallic character increases.

The periodic variation in electronic configuration as one move sequentially in increasing order of atomic number produces a periodic variation in properties.

As the elements are arranged in increasing order of atomic number, the metals with tendency to lose electrons are placed on the left and the metallic character decreases from left to right and increases down a group and non-metals with tendency to gain electrons are placed automatically on the right and the non-metallic character increase across a period and decreases down a group.

Metals are the elements which give away the electrons and those that accept electrons are generally non-metals. Metals are electropositive elements because they lose electrons to form positive ions. Non-metals are called electronegative elements because they gain electrons in chemical reactions to form negative ions.

(a) Since, the distance of the valence electrons from the nucleus keeps on increasing down the group, therefore, the ionization energy keeps on decreasing. Hence the reactivity of alkali metals increases from lithium to francium.

(b) As we move down a group, the size keeps on increasing, so it becomes more difficult for atoms to attract electrons. Thus reactivity of halogens decreases from Fluorine to Astatine.

(a) Cl < Cl¯

(b) Mg2+ < Mg+ < Mg

(c) O < N < P

(a) Thallium has the most metallic character since metallic character increases down the group

(b) Boron has the highest electronegativity since it has the smallest size in the group.

(c) 3. Since all the elements in a group have same number of valence electrons.

(d) BCl₃

(e) The elements in the group to the right of boron group would be less metallic as with the decrease in size and increase in atomic number, it will be more difficult for them to lose electrons