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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.

ChemistryClass 11CBSE

Why are neutrons considered 'neutral' particles, and what implication does this have for an atom's charge?

Neutrons are considered 'neutral' because they possess no electrical charge. This means they do not contribute to the overall electrical charge of an atom, only to its mass.The neutrality of neutrons is fundamental. While they add mass to the nucleus, they do not affect the balance between positive protons and negative electrons. Therefore, the overall charge of an atom is determined solely by the number of protons and electrons.

ChemistryClass 11CBSE

What would happen to an atom's overall charge if it gained an extra electron?

If an atom gained an extra electron, its overall charge would become negative, as it would have more negatively charged electrons than positively charged protons.Atoms are typically electrically neutral, meaning they have an equal number of protons and electrons. Gaining an electron introduces an additional negative charge without a corresponding positive charge, resulting in a net negative charge for the atom, forming an anion.

ChemistryClass 11CBSE

Compare and contrast the location and relative mass of protons and electrons within an atom.

Protons are located in the dense central nucleus of an atom and have a relatively large mass. Electrons, in contrast, orbit the nucleus and are significantly lighter, having a negligible mass compared to protons.Explnation:Protons are heavy, positively charged particles located in the nucleus. Electrons are much lighter, negatively charged particles that occupy the electron cloud surrounding the nucleus. This difference in mass and location is crucial for understanding atomic structure and behavior.

ChemistryClass 11CBSE

How is the mass number of an atom calculated based on its subatomic particles?

The mass number is calculated by adding the total number of protons and neutrons in the atom's nucleus.The mass number (A) represents the total number of nucleons (protons and neutrons) in an atom's nucleus. Since electrons have negligible mass compared to protons and neutrons, they are not included in the mass number calculation. This number gives an approximation of the atom's atomic mass.

ChemistryClass 11CBSE

Describe the role of the atomic number in determining the identity of an element.

The atomic number represents the number of protons in an atom's nucleus. This number is unique to each element and dictates its chemical properties, effectively identifying the element.The atomic number (Z) is a fundamental property of an atom. It defines the number of protons, which in turn determines the element's identity. For example, all atoms with 6 protons are carbon atoms, regardless of their number of neutrons or electrons. Changing the number of protons changes the element itself.

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