Atomic Structure

 

Atomic structure 

🧪 Relative Mass – Questions & Answers

Q1: What is meant by relative mass in atomic structure?

✔️ It is the mass of a particle compared to the mass of another particle, usually with the proton’s mass taken as 1.

Q2: Why do we use relative mass instead of actual mass in chemistry?

✔️ Because the actual masses of subatomic particles are extremely small and difficult to work with, so relative mass provides simpler comparison values.

Q3: What is the relative mass of a proton?

✔️ 1

Q4: What is the relative mass of a neutron?

✔️ 1

Q5: What is the relative mass of an electron?

✔️ Approximately 1/1836, meaning it is much lighter than a proton or neutron.

Q6: Which two particles contribute significantly to the mass of an atom?

✔️ Protons and neutrons

Q7: Why do we usually ignore the mass of electrons when calculating the mass number?

✔️ Because electrons are so light (relative mass ≈ 1/1836) that their mass is negligible compared to protons and neutrons.

Q8: If an atom has 8 protons, 8 neutrons, and 8 electrons, what is its approximate relative mass?

✔️ Relative mass ≈ Protons (8) + Neutrons (8) = 16

Q9: What is the mass number of an atom with 12 protons and 12 neutrons?

✔️ 24 (Protons + Neutrons = Mass Number)

Q10: Which subatomic particle has the smallest relative mass?

✔️ Electron

Q11: Which subatomic particles are found in the nucleus of an atom?

✔️ Protons and Neutrons

Q12: Which subatomic particle orbits around the nucleus?

✔️ Electrons

Q13: What is the approximate mass of an atom with 11 protons, 12 neutrons, and 11 electrons?

✔️ Relative mass ≈ Protons (11) + Neutrons (12) = 23

Q14: An element has a mass number of 35 and atomic number of 17. How many neutrons does it have?

✔️ 35 – 17 = 18 neutrons

Q15: Why are protons and neutrons called nucleons?

✔️ Because they both reside inside the nucleus of an atom.

Q16: Can electrons affect the mass number of an atom?

✔️ No, electrons are so light that they do not affect the mass number significantly.

Q17: If the number of neutrons increases in an atom, what happens to the mass number?

✔️ The mass number increases.

Q18: Do isotopes of the same element have the same relative mass?

✔️ No, isotopes have different relative masses due to different numbers of neutrons.

Q19: The mass number of Magnesium is 24, and it has 12 protons. How many neutrons are present?

✔️ 24 – 12 = 12 neutrons

Q20: What is the relative mass of 2 protons, 2 neutrons, and 2 electrons?

✔️ Protons (2 × 1) + Neutrons (2 × 1) + Electrons (≈ negligible) = 4

Q21: Why do electrons, despite being present, not contribute significantly to the mass of an atom?

✔️ Because their relative mass is extremely small compared to protons and neutrons.

Q22: What does the mass number of an atom represent?

✔️ The total number of protons and neutrons in the nucleus.

Q23: What is the relative mass of an ion compared to its neutral atom?

✔️ The same, because losing or gaining electrons doesn’t significantly change the mass.

Q24: If an atom loses two electrons, how does this affect its mass?

✔️ The mass remains almost the same, as electrons contribute negligible mass.

Q25: In terms of mass, which particle contributes more to an atom’s mass: a proton or an electron?

✔️ A proton contributes much more mass than an electron.

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🧪 Atomic Structure – 1 to 40 O Level Questions & Answers

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Set 1 – Basics of Atomic Structure

Q1: What is the smallest particle of an element that retains its properties?

✔️ An atom

Q2: Where are protons and neutrons located in an atom?

✔️ In the nucleus

Q3: What is the relative mass and charge of a proton?

✔️ Relative mass = 1, Charge = +1

Q4: What is the relative mass and charge of a neutron?

✔️ Relative mass = 1, Charge = 0 (neutral)

Q5: What is the relative mass and charge of an electron?

✔️ Relative mass ≈ 1/1836, Charge = -1

Q6: What does the atomic number of an atom represent?

✔️ The number of protons in the nucleus

Q7: How is the mass number of an atom calculated?

✔️ Mass number = Number of protons + Number of neutrons

Q8: In a neutral atom, the number of electrons is equal to the number of what?

✔️ Protons

Q9: What are isotopes?

✔️ Atoms of the same element with the same number of protons but different numbers of neutrons

Q10: What are the regions called where electrons are arranged around the nucleus?

✔️ Energy levels or shells

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Set 2 – Electron Arrangement and Ions

Q11: How many electrons can the first and second shells hold?

✔️ First shell = 2 electrons, Second shell = 8 electrons

Q12: What are the electrons in the outermost shell called?

✔️ Valence electrons

Q13: What type of ion is formed when an atom loses electrons?

✔️ A positive ion (cation)

Q14: What type of ion is formed when an atom gains electrons?

✔️ A negative ion (anion)

Q15: Where is almost all the mass of an atom concentrated?

✔️ In the nucleus

Q16: What is the electronic configuration of Sodium (Na) with atomic number 11?

✔️ 2, 8, 1

Q17: What subatomic particle determines the identity of an element?

✔️ Protons

Q18: What is the charge of the nucleus of an atom?

✔️ Positive, due to protons

Q19: Why is an atom electrically neutral?

✔️ Because the number of protons equals the number of electrons

Q20: What is meant by the term nucleon?

✔️ Protons and neutrons, found in the nucleus

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Set 3 – Calculations and Isotopes

Q21: What is the mass number of an atom with 17 protons and 18 neutrons?

✔️ 35

Q22: How do you calculate the number of neutrons in an atom?

✔️ Neutrons = Mass number – Atomic number

Q23: The element Carbon has an atomic number of 6. How many electrons does it have in a neutral atom?

✔️ 6 electrons

Q24: Define isotope with an example.

✔️ Atoms with same number of protons but different numbers of neutrons

Example: Carbon-12 and Carbon-14

Q25: Which subatomic particle contributes to both mass and positive charge?

✔️ Protons

Q26: Which subatomic particle contributes to mass but has no charge?

✔️ Neutrons

Q27: What is the relative charge on an atom when it loses 2 electrons?

✔️ +2

Q28: What happens to the size of an atom when it loses electrons?

✔️ It becomes smaller

Q29: What happens to the size of an atom when it gains electrons?

✔️ It becomes larger

Q30: Why do electrons revolve around the nucleus?

✔️ Due to electrostatic attraction between protons and electrons

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Set 4 – Applications and Examples

Q31: What do we call atoms or groups of atoms with a net electric charge?

✔️ Ions

Q32: What is the electron configuration of Oxygen (O) with atomic number 8?

✔️ 2, 6

Q33: What is the electron configuration of Magnesium (Mg) with atomic number 12?

✔️ 2, 8, 2

Q34: Name an element with a full outer shell of electrons.

✔️ Neon (Ne) or any noble gas

Q35: How many protons and electrons are present in a Cl⁻ ion? (Atomic number = 17)

✔️ 17 protons, 18 electrons

Q36: What is the significance of the outermost electrons in an atom?

✔️ They determine the chemical properties and reactivity

Q37: Which subatomic particle has negligible mass?

✔️ Electron

Q38: What is the relative mass of 2 protons, 2 neutrons, and 2 electrons?

✔️ Approximately 4 (electron mass is negligible)

Q39: Why do we ignore the mass of electrons in mass number calculations?

✔️ Their mass is extremely small

Q40: What is the mass number of an Oxygen atom with 8 protons and 8 neutrons?

✔️ 16

Happy learning 

Prepared by Noor E Alam 

University of Dhaka 

Chemistry, IGCSE