Chapter 4: Structure of the Atom

Play an AI-generated podcast conversation about this lesson

Which scientist is credited with the discovery of the atomic nucleus?

Ernest Rutherford (correct)

J.J. Thomson

E. Goldstein

Neils Bohr

What is the relationship between the mass of an electron and the mass of a hydrogen atom?

The mass of an electron is about 1 times 2000 the mass of a hydrogen atom. (correct)

The mass of an electron is about the same as the mass of a hydrogen atom.

The mass of an electron is about 2000 times the mass of a hydrogen atom.

The mass of an electron is about 1/2000 the mass of a hydrogen atom.

What is the charge of a neutron?

Varies depending on the atom

Positively charged

No charge (correct)

Negatively charged

Which model of the atom proposed that electrons are distributed in different shells with discrete energy around the nucleus?

Bohr's model Signup and view all the answers

What are atoms of different elements with the same mass number called?

Isobars Signup and view all the answers

What are canal rays?

Streams of positively charged particles produced in a discharge tube Signup and view all the answers

If an atom contains one electron and one proton, will it carry a net charge?

No, it will be electrically neutral Signup and view all the answers

According to Thomson's model of an atom, the positive charge is distributed in the form of:

A diffuse, positively charged sphere Signup and view all the answers

Which of the following analogies best represents Thomson's model of an atom?

A plum pudding with raisins distributed throughout Signup and view all the answers

Which scientist's discovery led to the failure of Dalton's atomic theory?

Thomson's discovery of electrons Signup and view all the answers

According to Bohr's model of the atom, why are atoms quite stable?

Electrons do not radiate energy while revolving in discrete orbits Signup and view all the answers

What subatomic particle was discovered in the nucleus of an atom according to Rutherford's model?

Protons Signup and view all the answers

According to Thomson's model, how is the atom as a whole neutral?

The positive and negative charges are distributed uniformly throughout the atom Signup and view all the answers

If the $\alpha$-particle scattering experiment is carried out using a foil of a metal other than gold, what observation would you expect?

The $\alpha$-particles would be scattered at larger angles Signup and view all the answers

What was the major contribution of Neils Bohr to the understanding of atomic structure?

He proposed the existence of discrete energy levels for electrons in an atom Signup and view all the answers

Which of the following experiments provided evidence that atoms are divisible and have smaller constituents?

Thomson's cathode ray experiment Signup and view all the answers

What is the overall charge of an atom in its neutral state?

Zero Signup and view all the answers

Which of the following statements about canal rays is correct?

Canal rays are streams of positively charged particles Signup and view all the answers

Which subatomic particle was discovered by J.J. Thomson through his cathode ray experiment?

Electron Signup and view all the answers

According to the Thomson model of the atom, what is the distribution of positive and negative charges within the atom?

Negative charges are concentrated in the center, with positive charges surrounding it Signup and view all the answers

What did Rutherford conclude about the space inside an atom based on the alpha-particle scattering experiment?

Most of the space inside the atom is empty because most alpha particles passed through the gold foil without deflection. Signup and view all the answers

Why did Rutherford conclude that the nucleus of an atom is very small?

Since the size of the nucleus is 105 times less than the radius of the atom. Signup and view all the answers

What was one of the main drawbacks of Rutherford's model of the atom?

It failed to describe how electrons lose energy and fall into the nucleus. Signup and view all the answers

According to Rutherford's nuclear model, where does nearly all of the mass of an atom reside?

In the positively charged centre called the nucleus. Signup and view all the answers

Why did Rutherford suggest that charged particles would radiate energy if they revolved in circular orbits?

Because any particle in a circular orbit would accelerate. Signup and view all the answers

What is the name of the subatomic particle discovered by Chadwick that has no charge and a mass nearly equal to that of a proton?

Neutron Signup and view all the answers

In the helium atom, which has an atomic mass of 4 u and two protons in its nucleus, how many neutrons are present?

1 Signup and view all the answers

According to the formula for the maximum number of electrons in a shell (2n^2), what is the maximum number of electrons that can be accommodated in the N-shell (n=4)?

32 Signup and view all the answers

Which of the following statements is true regarding the distribution of electrons in different orbits or shells of an atom?

The distribution of electrons in different shells was proposed by Bohr and Bury. Signup and view all the answers

In the representation of a neutron as 'n', what does the symbol 'n' signify?

The charge of the neutron Signup and view all the answers

According to Thomson's model of the atom, what is the arrangement of electrons within the atom?

Electrons are embedded in a positively charged sphere. Signup and view all the answers

What was the primary observation from Rutherford's alpha particle scattering experiment that contradicted Thomson's model?

Some alpha particles were deflected at large angles, indicating a dense, positive center in the atom. Signup and view all the answers

If an atom is electrically neutral, what can be inferred about the relationship between the positive and negative charges within the atom?

The positive and negative charges are equal in magnitude. Signup and view all the answers

What was the primary reason for Rutherford's choice of using a gold foil in his alpha particle scattering experiment?

Gold is a malleable material, allowing for the creation of an extremely thin foil. Signup and view all the answers

What property of alpha particles made them suitable for Rutherford's scattering experiment?

Alpha particles are doubly-charged helium ions with a high mass. Signup and view all the answers

Which of the following statements accurately describes the canal rays observed by Goldstein in his experiments?

Canal rays are positively charged particles that travel in the opposite direction of cathode rays. Signup and view all the answers

What is the primary difference between Thomson's and Rutherford's models of the atom?

Thomson's model assumed electrons were embedded in the atom, while Rutherford's model proposed electrons orbiting the nucleus. Signup and view all the answers

In Rutherford's alpha particle scattering experiment, what was the expected behavior of the alpha particles based on Thomson's model?

Alpha particles would experience small deflections due to interactions with the embedded electrons. Signup and view all the answers

Which of the following statements accurately describes the charge distribution within an atom according to Rutherford's model?

The positive charge is concentrated in a dense, central nucleus. Signup and view all the answers

What was the primary reason for selecting a gold foil that was approximately 1000 atoms thick in Rutherford's experiment?

To ensure that the alpha particles would interact with a sufficient number of atoms. Signup and view all the answers

What is the valency of magnesium and aluminium?

2 and 3 Signup and view all the answers

What is the valency of oxygen calculated based on electron distribution?

2 Signup and view all the answers

How is the maximum number of electrons in the N-shell (n=4) calculated?

32 Signup and view all the answers

How is valency determined for elements with nearly full outer shells like fluorine?

By subtracting the number of electrons from the octet. Signup and view all the answers

What is the significance of the combining capacity of an element, known as valency?

It determines the number of electrons gained, lost or shared for a full outer shell. Signup and view all the answers

Explain the distribution of electrons in a carbon atom.

2, 4 Signup and view all the answers

Describe the distribution of electrons in a sodium atom.

2, 8, 1 Signup and view all the answers

If the K and L shells of an atom are full, what is the total number of electrons in the atom?

18 Signup and view all the answers

What is the maximum number of electrons that can be accommodated in the outermost shell of an atom according to the Bohr-Bury model?

8 Signup and view all the answers

Explain why atoms with 8 electrons in their outermost shell show little chemical activity.

Zero valency Signup and view all the answers

Explain the concept of valency in atoms, and how it is related to the number of electrons in the outermost shell.

Valency is the combining capacity of atoms, determined by the number of electrons in the outermost shell. Atoms tend to react to achieve a fully-filled outermost shell, typically with 8 electrons. Signup and view all the answers

Describe the electron distribution in the N-shell (n=4) as per the electron distribution table given for the first 18 elements.

The N-shell can accommodate a maximum of 32 electrons. The electron distribution in the N-shell for the first 18 elements ranges from 0 to 18 electrons. Signup and view all the answers

What is the electronic configuration of Phosphorus (P) based on the electron distribution table provided?

The electronic configuration of Phosphorus is 2,8,5. It has 2 electrons in the K-shell, 8 in the L-shell, and 5 in the M-shell. Signup and view all the answers

Explain the significance of achieving an octet in the outermost shell of an atom.

Achieving an octet in the outermost shell makes an atom stable and less reactive. It involves atoms gaining, losing, or sharing electrons to reach 8 electrons in the outermost shell. Signup and view all the answers

Discuss the key differences between Bohr's atomic model and the earlier atomic models proposed by Thomson and Rutherford.

Bohr's model introduced discrete energy levels and orbits for electrons, unlike the continuous distribution in previous models. It also explained atomic stability with quantized energy levels. Signup and view all the answers

What is the valency of an element with Z=3? Name the element.

Valency is 1. Element is Lithium. Signup and view all the answers

In an atom, what is the maximum number of electrons that can be accommodated in the N-shell (n=4)?

32 electrons Signup and view all the answers

What is the correct electronic configuration of sodium?

2,8,1 Signup and view all the answers

In Rutherford's alpha-particle scattering experiment, what was responsible for the discovery of the Atomic Nucleus?

Atomic Nucleus Signup and view all the answers

How many valence electrons does a Cl- ion have?

8 Signup and view all the answers

Explain the maximum number of electrons that can be accommodated in the M shell of an atom.

18 electrons Signup and view all the answers

Define valency and provide the valency of silicon and oxygen.

Valency is the combining capacity of an atom. Silicon has a valency of 4, while oxygen has a valency of 2. Signup and view all the answers

Describe Bohr's model of the atom and explain why it was considered an improvement over previous models.

Bohr's model proposed that electrons move in fixed orbits around the nucleus and explained the stability of atoms. It was an improvement because it successfully explained the line spectra of elements. Signup and view all the answers

Summarize the rules for writing the distribution of electrons in the first eighteen elements' shells.

The distribution follows the pattern 2-8-8, starting with the K shell and then filling the L and M shells with electrons. Signup and view all the answers

Explain with examples the concept of isotopes and calculate the average atomic mass of a bromine atom given two isotopes.

Isotopes are atoms of the same element with different mass numbers. The average atomic mass of bromine is 79.9 u. Signup and view all the answers

Explain the concept of isobars in terms of atomic structure.

Isobars are atoms of different elements with different atomic numbers but the same mass number. Signup and view all the answers

Describe the electronic configuration of isotopes and isobars.

Isotopes have the same number of protons but different number of neutrons, leading to different atomic masses. Isobars have the same mass number but different atomic numbers. Signup and view all the answers

What is the significance of having complete atomic shells according to Bohr's atomic model?

Complete atomic shells lead to stability and less reactivity of the atom. Signup and view all the answers

How do electrons, protons, and neutrons contribute to the structure of an atom?

Electrons are negatively charged and orbit the nucleus; protons are positively charged and reside in the nucleus; neutrons have no charge and are also in the nucleus. Signup and view all the answers

Explain the concept of sub-atomic particles found in hydrogen isotopes.

Hydrogen isotopes consist of electrons, protons, and neutrons. Signup and view all the answers

Explain how to find the valency of chlorine, sulphur, and magnesium.

Chlorine has a valency of -1, sulphur has a valency of -2, and magnesium has a valency of +2. Signup and view all the answers

If the number of electrons in an atom is 8 and the number of protons is also 8, what is the atomic number of the atom and what is the charge on the atom?

The atomic number is 8 and the atom is neutral (charge of 0). Signup and view all the answers

Using Table 4.1, find the mass number of oxygen and sulphur atoms.

The mass number of oxygen is 16 and the mass number of sulphur is 32. Signup and view all the answers

What are isotopes and how do they differ from regular atoms?

Isotopes are atoms of the same element with the same atomic number but different mass numbers. They differ in the number of neutrons in the nucleus. Signup and view all the answers

Explain the concept of atomic number and how it is determined in an atom.

Atomic number is the number of protons in the nucleus of an atom. It is determined by the number of protons an atom possesses. Signup and view all the answers

What is the significance of the atomic number in defining elements?

The atomic number determines the identity of an element. All atoms of the same element have the same atomic number. Signup and view all the answers

Explain how the symbol of an element is written in atomic notation.

The symbol includes the atomic number (Z), mass number (A), and symbol of the element (e.g., C for carbon). Signup and view all the answers

Describe the distribution of positive and negative charges within an atom according to Bohr's model.

In Bohr's model, positive charges are concentrated in the nucleus, while negative charges (electrons) orbit around the nucleus in discrete energy levels. Signup and view all the answers

What is the maximum number of electrons that can be accommodated in the N-shell (n=4) according to the formula for electron distribution in shells?

The maximum number of electrons in the N-shell (n=4) is 32. Signup and view all the answers

Explain why atoms are quite stable according to Bohr's atomic model.

Atoms are stable in Bohr's model because electrons occupy fixed energy levels and do not emit radiation while orbiting the nucleus. Signup and view all the answers