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

Samacheer Kalvi 7th Standard Science Book Back 1 Mark and 2 Mark Question & Answers uploaded online and available PDF for free download. Class 7th New Syllabus Science Term 1 book back question & answer solutions guide available below for English Medium. Class Seventh Std Science English Medium Term 1 Unit 4 Atomic Structure book back answers given below. Students looking for class 7th Term I Unit 4 Questions and Answers can check below.

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Samacheer Kalvi 7th Science Book Back Term 1 Unit 4 Solution Guide PDF:

TN State Board Class 7th Science Subject Term 1 Unit 4 one mark and two mark solutions guide PDF available below.

Science – Term 1

Unit 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 revolving 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 particles
2. Protons, Neutrons
3. electrons
4. CH₄
5. 2

III. Match the following :

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 a molecule.
Answer:
(False) Correct statement: The basic unit of an element is an 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 an 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 the nucleus.
Reason: The nucleus is at the center.
Answer:
Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

3. Assertion: The number of protons and neutrons is the atomic number.
Reason: The mass number is the 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 the 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 are the characteristics of the proton?
Answer:
The proton is a positively charged particle and is located in the nucleus. Its positive Charge is of the same magnitude as that of the electron’s negative charge.

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

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