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ChemistryClass 11CBSE

What is the primary force that holds the protons and neutrons together within the nucleus, despite the electrostatic repulsion between protons?

The primary force is the strong nuclear force (or strong interaction).Protons, being positively charged, naturally repel each other. The strong nuclear force is an extremely powerful attractive force that acts over very short distances, overcoming this electrostatic repulsion to bind the nucleons (protons and neutrons) together in the nucleus.

ChemistryClass 11CBSE

Explain why the mass number is always a whole number, even though atomic masses often have decimal values.

The mass number represents the count of whole protons and neutrons in a single atom's nucleus, which are discrete particles. Atomic masses, however, are weighted averages of the masses of all naturally occurring isotopes of an element, which often results in decimal values.

ChemistryClass 11CBSE

If an atom has an atomic number of 20 and is electrically neutral, how many protons, neutrons, and electrons could it potentially have (give one possible combination)?

Protons = 20, Electrons = 20. For neutrons, it could vary, for example, 20 neutrons, making the mass number 40.Atomic number 20 means 20 protons. For neutrality, it must have 20 electrons. The number of neutrons can vary, creating isotopes. A common isotope for an element with 20 protons (Calcium) often has 20 neutrons.

ChemistryClass 11CBSE

How does the concept of 'orbiting' electrons relate to the overall size and volume of an atom?

The 'orbiting' electrons occupy a vast region of space around the nucleus, defining the overall size and volume of the atom. The nucleus itself is extremely small in comparison.Despite the nucleus containing almost all the mass, the electrons, due to their rapid motion and the probabilistic nature of their location, determine the atomic radius and, consequently, the atom's volume. The atom is mostly empty space.

ChemistryClass 11CBSE

What would be the net charge of an atom if it had 11 protons, 12 neutrons, and 10 electrons?

The net charge would be +1.The number of protons (positive charges) is 11, and the number of electrons (negative charges) is 10. The net charge is 11 - 10 = +1. Neutrons do not contribute to the charge.

ChemistryClass 11CBSE

Why is the phrase 'Atomic number determines the element' a fundamental concept in chemistry?

This phrase is fundamental because the atomic number, which is the number of protons, uniquely defines an element's identity and its chemical properties. Any change in the number of protons results in a different element.

ChemistryClass 11CBSE

If an atom has 6 protons, 6 neutrons, and 6 electrons, what is its atomic number and mass number?

Atomic number = 6, Mass number = 12.Atomic number is the number of protons (6). Mass number is the sum of protons and neutrons (6 + 6 = 12).

ChemistryClass 11CBSE

Describe the general arrangement of subatomic particles within an atom, including their relative positions.

An atom consists of a dense, positively charged nucleus at its center, composed of protons and neutrons. Negatively charged electrons orbit this nucleus in a cloud-like region.The atomic model describes a central nucleus containing protons and neutrons, which accounts for most of the atom's mass and positive charge. Electrons, with their much smaller mass and negative charge, occupy the vast space surrounding the nucleus.

ChemistryClass 11CBSE

In a neutral atom, if there are 15 protons, how many electrons are present?

There are 15 electrons present.For a neutral atom, the number of positively charged protons must equal the number of negatively charged electrons to balance the overall charge.

ChemistryClass 11CBSE

What would be the effect on an atom's atomic number if it gained or lost neutrons?

Gaining or losing neutrons would not affect an atom's atomic number, as the atomic number is determined solely by the number of protons.The atomic number is fixed by the number of protons. Changing the number of neutrons only changes the mass number and creates an isotope of the same element, it does not change the element's identity or its atomic number.

ChemistryClass 11CBSE

Why is the mass of electrons generally disregarded when calculating the overall mass of an atom?

The mass of electrons is generally disregarded because it is extremely small, approximately 1/1836th the mass of a proton or neutron, making its contribution to the atom's total mass negligible.The vast majority of an atom's mass comes from its protons and neutrons. While electrons do have mass, it's so tiny in comparison that it doesn't significantly impact the overall atomic mass, especially when calculating the mass number.

ChemistryClass 11CBSE

If two atoms have the same number of protons but different numbers of neutrons, what are they called?

They are called isotopes.Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons.

ChemistryClass 11CBSE

An atom has an atomic number of 17 and a mass number of 35. How many neutrons does it have?

The atom has 18 neutrons.Number of neutrons = Mass number - Atomic number. So, 35 - 17 = 18 neutrons.

ChemistryClass 11CBSE

What is the significance of the nucleus in an atom, considering the location of protons and neutrons?

The nucleus is the dense, central part of an atom where almost all of its mass is concentrated, due to the presence of protons and neutrons. It also contains all of the atom's positive charge.The nucleus is the heart of the atom, containing the heavy protons and neutrons. It accounts for virtually all of the atom's mass and its entire positive charge, which attracts the orbiting electrons.

ChemistryClass 11CBSE

How do the charges of protons and electrons ensure the overall electrical neutrality of a typical atom?

In a typical, neutral atom, the number of positively charged protons is equal to the number of negatively charged electrons. These equal and opposite charges cancel each other out, resulting in a net electrical charge of zero.The balance between the positive charge of protons and the negative charge of electrons is what makes an atom electrically neutral. Any imbalance leads to the formation of an ion.

ChemistryClass 11CBSE

If an atom loses an electron, what type of ion is formed, and what is its overall charge?

If an atom loses an electron, a cation is formed, and its overall charge will be positive.Losing a negatively charged electron leaves the atom with more protons than electrons, resulting in a net positive charge. Positively charged ions are called cations.

ChemistryClass 11CBSE

Explain why electrons are described as 'lightweight particles that orbit the nucleus'.

Electrons are described as 'lightweight' because their mass is significantly smaller than that of protons and neutrons. They 'orbit the nucleus' because they are found in a cloud-like region around the central nucleus, attracted by the positive charge of the protons.The mass of an electron is approximately 1/1836th the mass of a proton. Their motion around the nucleus is often described as 'orbiting' or existing in 'electron shells' or 'orbitals,' driven by the electrostatic attraction to the positively charged nucleus.

ChemistryClass 11CBSE

Consider an atom with an atomic number of 8. What element is this, and how many protons does it have?

This element is Oxygen, and it has 8 protons.The atomic number directly corresponds to the number of protons and uniquely identifies an element. An atomic number of 8 signifies Oxygen.

ChemistryClass 11CBSE

What distinguishes an isotope of an element from its standard form?

An isotope of an element has the same number of protons (and thus the same atomic number) but a different number of neutrons, leading to a different mass number.Isotopes are atoms of the same element that differ in their neutron count. Because the number of protons defines the element, isotopes of the same element will have identical chemical properties but may vary in physical properties due to their mass difference.

ChemistryClass 11CBSE

If an atom has 10 protons and 12 neutrons, what is its mass number?

The mass number is 22.The mass number is the sum of protons and neutrons. In this case, 10 protons + 12 neutrons = 22.

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