Tamil Nadu Board Class 7 Science Chapter 4 Atomic Structure

 

5. Why neutrons are called neutral particles?

Neutrons are called neutral particles because they have no electrical charge.

 

[VIII] Answer briefly.

1. Distinguish isotopes from isobar.

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons, resulting in different mass numbers. For example, Carbon-12 and Carbon-14 are isotopes of carbon.Isobars are atoms of different elements that have the same mass number but different atomic numbers. For example, Argon-40 and Calcium-40 are isobars.

 

2. What are isotones? Give one example.

Isotones are atoms of different elements that have the same number of neutrons but different numbers of protons. For example, Carbon-14 (6 protons and 8 neutrons) and Nitrogen-15 (7 protons and 8 neutrons) are isotones because they both have 8 neutrons.

 

3. Differentiate mass number from atomic number.

The atomic number is the number of protons in the nucleus of an atom, denoted by ZZ.

The mass number is the total number of protons and neutrons in the nucleus of an atom, denoted by AA. It is calculated as A=Z+NA=Z+N, where NN is the number of neutrons.

 

4. The atomic number of an element is 9. It has 10 neutrons. Find the element from the periodic table. What will be its mass number?

    The element with atomic number 9 is fluorine (F).

    Its mass number is calculated as follows:

•     Mass number=Number of protons+Number of neutrons=9+10=19
•     Mass number=Number of protons+Number of neutrons=9+10=19
•     Therefore, the mass number of the element is 19.

 

[IX] Answer in detail.

1. Draw the structure of an atom and explain the position of the sub-atomic particles.

Do This On Your Own.

 

2. The atomic number and the mass number of an element is 26 and 56 respectively. Calculate the number of electrons, protons and neutrons in its atom. Draw the structure.

    Atomic number (Z) = 26: This means there are 26 protons and, since the atom is neutral, 26 electrons.

•     Mass number (A) = 56: This is the sum of protons and neutrons.
•     Number of neutrons=Mass number−Atomic number=56−26=30
•     Number of neutrons=Mass number−Atomic number=56−26=30

 

• Number of Protons: 26
• Number of Electrons: 26
• Number of Neutrons: 30

 

3. What are nucleons? Why are they called so? Write the properties of the nucleons.

Nucleons:

Nucleons are particles found in the nucleus of an atom, specifically protons and neutrons.

They are called nucleons because they are located in the nucleus of the atom.

Properties of Nucleons:

Protons:

• Positively charged with a relative charge of +1.
• Mass is approximately 1 atomic mass unit (amu).
• Determines the atomic number and identity of an element.

Neutrons:

• Neutrally charged with no electrical charge.
• Mass is slightly greater than that of a proton but approximately 1 amu.
• Contributes to the mass number and stability of the nucleus.

 

4. Define valency. What is the valency of the element with atomic number 8? What is the compound format by this element with hydrogen?

Valency:Valency is the combining capacity of an element, determined by the number of electrons in the outermost shell that can be shared, gained, or lost to form chemical bonds.

Valency of the Element with Atomic Number 8:

The element with atomic number 8 is oxygen.

Oxygen has 6 electrons in its outermost shell (2 in the first shell and 6 in the second shell).

To achieve a stable electron configuration, oxygen needs 2 more electrons, giving it a valency of 2.

 

Compound Formed by This Element with Hydrogen:

The compound formed is water (H₂O).

Each oxygen atom can form bonds with two hydrogen atoms, sharing electrons to complete its outer shell.

H−O−H

H−O−H