Lakhmir Singh solutions for केमिस्ट्री [अंग्रेजी] कक्षा १० आईसीएसई chapter 1 - Periodic Properties and Variations of Properties [Latest edition]

State whether the following statement is True or False.

Due to repetition of electronic configuration, repetition of properties takes place.

State whether the following statement is True or False.

Elements having the same number of electrons in the last shell lie in the same vertical column.

State whether the following statement is True or False.

Hydrogen and chlorine are placed in the same group.

State whether the following statement is True or False.

Lanthanides and actinides are placed in the third group.

At the time of Mendeleev, there were ______ elements known.

Group 17 elements are also called as ______.

Repetition of properties of elements with increasing atomic ______ is called periodicity.

The problems in Mendeleev periodic table were related to ______ of elements.

The horizontal and vertical rows in a periodic table are known as ______.

The arrangement of elements in the Modern Periodic Table is based on their ______.

What do you understand by electronic configuration?

How did the anomaly of putting isotopes together has been resolved in the modern periodic table?

Answer the following.

Why do the elements belonging to the same group have similar chemical properties?

Define the term periodicity.

State the modern periodic law for the classification of elements. How many (i) groups and (ii) periods are there in the modern periodic table?

State the limitation of the modern periodic table.

What were the criteria used by Mendeleev in creating his Periodic Table?

Write a short note on groups present in long form of periodic table.

Comment about the chemical properties of the elements of the same group.

State whether the following statement is True or False.

Electron affinity increases with a decrease in atomic size.

State whether the following statement is True or False.

Atomic radius decreases along a period.

State whether the following statement is True or False.

The tendency to lose electrons decreases as you move down a group.

Metallic character ______ down the group.

Valency of elements ______ and then ______ as we move across the period while it remains the same down the group.

The more is the ______ charge, the more will be the electron affinity.

The ______ radius is half the distance between the nuclei of two identical non-bonded adjacent atoms.

Which one of the following statements is not correct about the trends in the properties of the elements of a period on going from left to right?

An element X has mass number 40 and contains 21 neutrons in its atom. To which group of the Periodic Table does it belong?

Which one of the following statements is not correct about the trends in the properties of the elements of a group on going down in a group?

Define valence electrons.

How does non-metallic character vary in a period?

Which is the most electronegative element in the periodic table?

Why electron affinity decreases on moving downwards in the group?

Why does electron gain enthalpy has a negative value?

How do you calculate the possible valency of an element from the electronic configuration of its atoms?

The atomic numbers of three elements, X, Y and Z are 9, 11 and 17 respectively. Which two of these elements will show similar chemical properties? Why?

How does the size of atoms (atomic size) generally vary in going from left to right in a period of the periodic table? Why does it vary this way?

F, Cl and Br are the elements each having seven valence electrons. Which of these (i) has the largest atomic radius, (ii) is most reactive? Justify your answer, stating the reason for each.

Why does chlorine has the highest electron gain enthalpy instead of fluorine?

The atomic number of an element is 16. Predict:

1. the number of valence electrons in its atom;
2. its valency;
3. its group number;
4. whether it is a metal or a non-metal;
5. the nature of the oxide formed by it.

How are the following related?

Number of valence electrons of different elements in the same group.

How are the following related?

Number of shells of elements in the same period.

How do the following change?

Number of shells of elements as we go down a group.

How do the following change?

Number of valence electrons of elements on moving from left to right in a period.

How do the following change?

Atomic radius in moving from left to right along a period.

How do the following change?

Atomic size down a group.

An ice cube made up of normal water floats in liquid water, while that made up of heavy water sinks in the normal liquid water. This is due to the fact that in heavy water, each molecule of water has two deuterium atoms instead of the two hydrogen atoms. Further, a deuterium atom differs from a hydrogen atom by the only fact that deuterium has one neutron in its nucleus along with one proton, while the hydrogen atom has only one proton in its nucleus.

Considering the fact that an extra neutron in the deuterium nucleus does not increase the volume ofthe heavy water molecule, estimate the percentage difference in densities of normal water and heavy water.

State whether the following statement is True or False.

Metals have a tendency for losing electrons and gaining a positive charge.

State whether the following statement is True or False.

The metallic character of alkalis decreases from lithium to francium.

State whether the following statement is True or False.

Halogens are strong oxidising agents since they easily accept electrons.

State whether the following statement is True or False.

Sodium combine with bromine to form electrovalent compound.

Elements which have an n/p ratio around ______ are stable.

Alkali metals form ______ compounds with non-metals.

Due to their high reactivity halogens exist as ______ molecules.

Atomic number is ______.

Mass number is ______.

Alkali metals are ______.

Halogens are ______.

Give two examples of alkaline earth metals?