Lakhmir Singh & Manjit Kaur Test: Structure of the Atom - Free MCQ

Answer:
The nucleus consists of protons and neutrons. Here is a detailed explanation of the components of the nucleus:
1. Protons:
- Protons are positively charged particles found in the nucleus of an atom.
- They have a mass of approximately 1 atomic mass unit (amu).
- The number of protons in an atom determines its atomic number, which defines the element.
2. Neutrons:
- Neutrons are neutral particles found in the nucleus of an atom.
- They have a mass similar to protons, approximately 1 amu.
- The number of neutrons in an atom can vary, resulting in different isotopes of an element.
3. Electrons:
- Electrons are negatively charged particles found in energy levels or shells outside the nucleus.
- They have a much smaller mass compared to protons and neutrons.
- The number of electrons in an atom is equal to the number of protons, ensuring overall neutrality.
Summary:
- The nucleus of an atom consists of protons and neutrons.
- Protons carry a positive charge and define the atomic number of an element.
- Neutrons are neutral particles and contribute to the mass of the atom.
- Electrons orbit around the nucleus in energy levels.

Valence Electrons in Sodium (Na)

• Sodium (Na) is a chemical element with atomic number 11.
• It belongs to group 1 of the periodic table, also known as the alkali metals group.
• The number of valence electrons in an atom is determined by its group number.
• Since sodium is in group 1, it has 1 valence electron.
• In the case of sodium, it readily loses its single valence electron to achieve a stable electron configuration, forming a Na+ ion.

The mass number, also called atomic mass number or nucleon number, is the total number of protons and neutrons in an atomic nucleus. It is approximately equal to the atomic mass of the atom expressed in atomic mass units.

Atomic number is a fundamental property of an element, defined as the number of protons present in its nucleus. Here are some key points:

• The atomic number is denoted by the symbol Z.
• For example, hydrogen has an atomic number of 1, indicating it has one proton.
• Carbon, on the other hand, has an atomic number of 6, meaning it contains six protons

The correct option is D.
The atomic size is of the order of 10⁻⁸
cm or 10⁻¹⁰ m or one angstrom unit.
On the other hand, the radius of an atomic nucleus is of the order of 10⁻¹³
cm or 10⁻¹⁵ m or one Fermi unit.

According to the question, we need to determine the maximum number of electrons that can be accommodated in the nth level.

To solve this problem, we can use the formula for the maximum number of electrons in a specific energy level. The formula is given by:
Maximum number of electrons = 2n²
Where:
- n represents the energy level or the principal quantum number.
Let's break down the solution into steps:
Step 1: Substitute the value of n into the formula.
- We are given the value of n as the nth level.
Step 2: Calculate the maximum number of electrons.
- Square the value of n (n²).
- Multiply the squared value by 2 (2n²).
Step 3: Determine the final answer.
- The maximum number of electrons that can be accommodated in the nth level is equal to the result obtained from step 2.
Therefore, the correct answer is option B: 2n².

Number of Electrons in Argon.

• Argon is a chemical element with the atomic number 18.
• As per the periodic table, the atomic number of an element represents the number of protons in the nucleus of an atom.
• Since atoms are electrically neutral, the number of electrons in an atom of Argon is also 18.

The correct option is D.
 Hydrogen is one of two stable isotopes of hydrogen (the other being protium, or hydrogen-1). The nucleus of a deuterium atom, called a deuteron, contains one proton and one neutron, whereas the far more common protium has no neutrons in the nucleus.

Electrons in the valence shells of Sodium and Calcium:

Electronic configuration of Na is 2, 8, 1. Therefore, Na has 1 electron in its valence shell.

Electronic configuration of Ca is 2, 8, 8, 2. Therefore, Ca has 2 electrons in its valence shell

Both statements describe the limitations of the Rutherford model and how they lead to instability in atoms, which was later addressed by the Bohr model.

Statement 1: This is consistent with Rutherford's model, where he proposed that the electron orbits the nucleus in a circular path. Since the electron is accelerating in this orbit, classical electromagnetic theory states that it should emit radiation and lose energy over time. This leads to the electron's energy decreasing as it radiates energy.
Statement 2: This follows logically from Statement 1. Since the electron in Rutherford's model radiates energy and loses it over time, it would move closer to the nucleus as its energy decreases. Eventually, the electron would spiral into the nucleus, causing the atom to collapse. This would make the atom unstable in the Rutherford model.

Rutherford's experiment with alpha particles involved directing them at a thin gold foil and observing their deflection. The main goal was to investigate the structure of the atom. The experiment led to the discovery that most of the atom is empty space and that there is a small, dense, positively charged nucleus at the center. It was not aimed at studying the arrangement of electrons but rather to gain insight into the overall atomic structure and discover the presence of the nucleus.

Thomson compared his model of the atom to a Christmas pudding, where the positive charge is the pudding itself and the electrons are the currants embedded within it.