Atomic Structure Book Back Questions 7th Science Lesson 4
7th Science Lesson 4
4] Atomic Structure
Book Back Questions with Answer and Do You Know Box Content
Do You Know?
Nanometre is the smallest unit used to measure small lengths. One metre is equal to 1 x 10-9 nm or one nano meter is equal to 1 x 10-9 m.
You have around 7 billion atoms in your body, yet you replace about 98% of them every year!
Is the structure of the atom the same as the structure of the solar system? Yes! It is similar to the solar system. It has a core centre called nucleus and it has paths called orbits around the nucleus.
Isotopes: Atoms of the same element can have different number of neutrons. Such atoms will have same atomic number but different mass numbers. These atoms are called isotopes. For example, Hydrogen has three isotopes ___ Hydrogen (1H1), Deuterium (1H2), and Tritium (1H3).
Isobars: Atoms that have the same mass number but different atomic numbers. For example, Calcium – 40 and Argon – 40
WHAT MAKES ATOMS STICK TOGETHER? Electrons carry a negative electric charge and protons carry a positive charge. The attraction between them holds electrons in orbits.
Choose the best answers:
1. The basic unit of matter is ______________
(a) Element
(b) Atom
(c) Molecule
(d) Electron
2. The subatomic particle revolve around the nucleus is ______________
(a) Atom
(b) Neutron
(c) Electron
(d) Proton
3. _______________ is positively charged.
(a) Proton
(b) Electron
(c) Molecule
(d) Neutron
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
5. __________________ nucleons comprises of
(a) Protons and electrons
(b) Neutrons and electrons
(c) Protons and neutrons
(d) Neutrons and Positron
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 is _______________
Match the following:
1. Valency – Fe
2. Neutral Particle – Proton
3. Iron – Electron in the outermost orbit
4. Hydrogen – Neutron
5. Positively charged particle – Monovalent
State true or false. If false, correct the statement:
1. The basic unit of an element is molecule.
2. The electrons are positively charged.
3. An atom is electrically neutral.
4. The nucleus is surrounded by protons.
Complete the analogy:
1. Sun: Nucleus, planets: _______________
2. Atomic number: ______________, mass number: number of protons and neutrons.
3. K: Potassium, C: ________________
Consider the statements given below and choose the correct option:
(a) If both assertion and reason are true and reason is the correct explanation of assertion
(b) If both assertion and reason are true but reason is not the correct explanation of assertion
(c) If assertion is true but reason is false
(d) If assertion is false but reason is true
Consider the statements given below and choose the correct option:
(a) If both assertion and reason are true and reason is the correct explanation of assertion
(b) If both assertion and reason are true but reason is not the correct explanation of assertion
(c) If assertion is true but reason is false
(d) If assertion is false but reason is true
1. Assertion: An atom is electrically neutral.
Reason: Atoms have equal number of protons and electrons.
2. Assertion: The mass of an atom is the mass of nucleus.
Reason: The nucleus is at the centre.
3. Assertion: The number of protons and neutrons is atomic number.
Reason: The mass number is sum of protons and neutrons.
Answers:
Choose the best answers:
1. Atom 2. Electron 3. Proton 4. Number of protons 5. Protons and Neutrons
Fill in the blanks:
1. Electrons 2. Positive and negative charge 3. Electrons 4. CH4 5. 2
Match the following:
1. Electron in the outermost orbit 2. Neutron 3. Fe 4. Monovalent 5. Proton
State True or False:
1. False
Correct Statement: The basic unit of an element is an atom.
2. False
Correct Statement: The electrons are negatively charged.
3. True
4. False
Correct Statement: The nucleus is surrounded by electrons.
Complete the analogy:
1. Electrons 2. Number of protons 3. Carbon
Consider the statements given below and choose the correct option:
1. Assertion is true but reason is false.
2. Assertion is false but reason is true
3. Assertion is false but reason is true.