Samacheer Kalvi 7th Science Term 1 Unit 4 Solutions

Samacheer Kalvi 7th Science Term 1 Unit 4 Book Back Question and Answers/Solutions:

Samacheer Kalvi Class 7th Std Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 7th Standard New Syllabus 2022 to 2023 Book Back Question & Answer solutions available for both English and Tamil Medium. Class 7 New Science Book Term 1 Unit 4 – Atomic Structure Answers/Solutions Guide are provided on this page. 7th Std Science Book is of 1st Term consists of 7 units, 2nd and 3rd Term consists of 6 units. All Units/Chapters of Term 1st, 2nd, 3rd Science Book Back One, and Two Mark Solutions are given below.

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Samacheer Kalvi 7th Science Book Back Chapter 4 Term 1 Answers/Solutions Guide PDF:

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7th Science – Term 1 Chapter 4

Atomic Structure

 

I. Choose the appropriate answer:

1. The basic unit of matter is __________
(a) Element
(b) Atom
(c) Molecule
(d) Electron
Answer:
(b) Atom

2. The subatomic particle revolve around the nucleus is __________
(a) Atom
(b) Neutron
(c) Electron
(d) Proton
Answer:
(c) Electron

3. __________ is positively charged.
(a) Proton
(b) Electron
(c) Molecule
(d) Neutron
Answer:
(a) Proton

4. The atomic number of an atom is __________
(a) Number of neutrons
(b) Number of protons
(c) Total number of protons and neutrons
(d) Number of atoms
Answer:
(b) Number of protons

5. __________ Nucleons comprises of
(a) Protons and electrons
(b) Neutrons and electrons
(c) Protons and neutrons
(d) Neutrons and Positron
Answer:
(c) Protons and neutrons

II. Fill in the blanks

  1. The smaller particles found in the atom is called _____
  2. The nucleus has _____ and _____
  3. The _____ revolve around the nucleus.
  4. If the valency of carbon is 4 and that of hydrogen is 1, then the molecular formula of methane is _____
  5. There are two electrons in the outermost orbit of the magnesium atom. Hence, the valency of magnesium _____

Answer:

  1. sub-atomic particels
  2. Protons, Neutrons
  3. electrons
  4. CH4
  5. 2

III. Match the following :

1. Valency (a) Fe
2. Neutral Particle (b) Proton
3. Iron (c) Electrons in the outermost Orbit
4. Hydrogen (d) Neutron
5. Positively charged Particle (e) Monovalent

Answer:

1 – c; 2 – d; 3 – a; 4 – e; 5 – b




IV. True or False. If False, give the correct statement (T/F).

1. The basic unit of an element is molecule.
Answer:
(False) Correct statement: The basic unit of an element is atom.

2. The electrons are positively charged.
Answer:
False. Correct statement: The electrons are negatively charged.

3. An atom is electrically neutral.
Answer:
True

4. The nucleus is surrounded by protons.
Answer:
(False) Correct statement: The nucleus is surrounded by electrons.

V. Complete the analogy.

  1. Sun: Nucleus, planets: ______
  2. Atomic number: ______ , Mass number: number of protons and neutrons.
  3. K: Potassium, C: ______.

Answer:

  1. electrons
  2. Number of protons
  3. Carbon

VI. Assertion and reason.

1. Assertion : An atom is electrically neutral.
Reason : Atoms have equal number of protons and electrons.
Answer:
Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

2. Assertion : The mass of an atom is the mass of nucleus.
Reason : The nucleus is at the centre.
Answer:
Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

3. Assertion : The number of protons and neutrons is atomic number.
Reason : The mass number is sum of protons and neutrons.
Answer:
Assertion is false but the reason is true statement.
Correct statement: The number of protons and neutrons is mass number.

VII. Give very short answer.

1. Define an atom.
Answer:
An atom is the smallest particle of a chemical element that retains its chemical properties.

2. Name the sub-atomic particles.
Answer:
Proton, Electron, Neutrons.

3. What is atomic number?
Answer:
The number of electrons or protons in an atom is called the atomic number of that atom. It is represented by the letter Z.

4. What is the characteristics of proton?
Answer:
The proton is the positively charged particle and its located in the nucleus. Its positive Charge is of the same magnitude as that of the electron’s negative charge.

5. Why neutrons called neutral particles?
Answer:
Neutrons are the particles in an atom that have a neutral change (no charge). They are not positive like protons. They are not negative like electrons. So they are called as neutral particles.

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