The Nucleus of An Atom
The nucleus of an atom is the focal locale of an atom where most of the mass is concentrated. Through the dispersing of alpha particles explored by Rutherford, we discovered that the nucleus of an atom contains a more significant part of the mass of the atom. Numerically, the nucleus of an atom possesses almost nearly 10-14 times the volume of the atom yet contains 99.99% of the atomic mass. The nucleus of an atom is little to the point that if you extended an atom to occupy a room, the nucleus of an atom would at present be no bigger than a pinhead!
Atomic Mass
An Atom is tiny, and in this manner, its mass is additionally relatively minute. An ordinary unit of mass, such as a Kilogram (Kg), can't be utilized to gauge something as small as an atom, and to deal with this agenda, researchers have made another unit of mass. This is termed as Atomic Mass Unit with symbol u. Its reference is taken as Carbon-12, and 1 Atomic Mass unit is equivalent to 1/twelfth the weight of one atom of Carbon 12.
The mass of a hydrogen atom can be expressed as follows:
1 u = one particle of C-12/12 = 1.992647 10-26/12 kg
1 u = 1.660539 10-27 kg
This is the mass of a hydrogen atom.
Composition of Nucleus of an Atom
The nucleus of an atom consists of proper and tightly arrangement of protons and neutrons. These are the two solid particles in an atom, and consequently, 99.9% of the mass is gathered in the nucleus. Of the two, the protons have a net positive charge. Henceforth, on the whole, the nucleus of an atom is positively charged, and the electrons which are negatively charged rotate around the center of the nucleus. The atomic powers holding the protons and the neutrons are also tremendous since the mass concentration at the nucleus of an atom is vast. The protons are in such close region to one another inside the tiny nucleus, and in this way, the electrostatic forces of repulsion likewise act inside the nucleus. Nuclear energy depends on only discharging the energy caught in the nucleus of an atom. The complete number of protons is equivalent to the number of electrons rotating around the nucleus, and henceforth the atom, in general, is electrically neutral.
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Some Interesting Facts of an Atom
There are more than 100 various types of atoms. Around 92 of them usually happen, while the rest are made in labs. An addition of more protons to an atomic nucleus helps in making new atoms.
The first atom made by man was technetium, which has 43 protons.
These new atoms (components) are temperamental and rot into tiny atoms quickly. Ordinarily, we just realize another atom was made by distinguishing the tiny atoms from this rot.
The parts of an atom are held together by three powers. Protons and neutrons are held together by both strong and weak atomic powers.
The electrical attraction contains electrons and protons. Electrical repugnance repulses protons from one another, but the attraction of the nuclear force is a lot stronger than electrical repulsion.
"Atom" originates from the Greek word for "uncuttable." The name originates from the fifth century BCE Greek savant Democritus, who accepted matter composed of particles that couldn't be cut into littler particles.
Atoms are exceptionally little. The typical atom is around one-tenth of a billionth of a meter over. The most significant atom (caesium) is roughly multiple times greater than the smallest atom (helium).
Even though atoms are the smallest unit of a component, they comprise of significantly lower particles called quarks and leptons. An electron is a lepton. Protons and neutrons consist of three quarks each.
FAQs on Nucleus of an Atom and It's Composition
1. What is the composition of the nucleus of an atom according to the Class 12 Physics syllabus?
The nucleus, located at the center of an atom, is composed of two types of subatomic particles: protons and neutrons. Collectively, these particles are known as nucleons. Protons carry a positive electric charge, while neutrons are electrically neutral. The nucleus contains almost all of the atom's mass and is responsible for its positive charge.
2. How is a specific nucleus or isotope represented using standard notation?
A specific nucleus is represented by the symbol AZX, where:
- X is the chemical symbol of the element.
- Z is the atomic number, which represents the number of protons.
- A is the mass number, which represents the total number of protons and neutrons (nucleons).
From this notation, the number of neutrons (N) can be calculated as N = A - Z. For example, the nucleus of Carbon-12 is written as 126C, indicating it has 6 protons and 12 - 6 = 6 neutrons.
3. What is the difference between isotopes, isobars, and isotones?
These terms describe different relationships between atomic nuclei:
- Isotopes are nuclei of the same element that have the same number of protons (same Z) but a different number of neutrons (different A). For example, Carbon-12 (12C) and Carbon-14 (14C) are isotopes.
- Isobars are nuclei of different elements that have the same mass number (same A) but different numbers of protons (different Z). For example, Argon-40 (4018Ar) and Calcium-40 (4020Ca) are isobars.
- Isotones are nuclei of different elements that have the same number of neutrons (same N = A-Z). For example, Chlorine-37 (3717Cl) and Potassium-39 (3919K) are isotones, as both have 20 neutrons.
4. How is the size of an atomic nucleus related to its mass number?
The size (radius) of an atomic nucleus is not fixed but can be estimated based on its mass number (A). Experimental results show that the radius R of a nucleus is proportional to the cube root of its mass number. This relationship is given by the empirical formula:
R = R₀A1/3
Here, R₀ is a constant known as the nuclear radius parameter, approximately equal to 1.2 x 10-15 m (or 1.2 femtometers). This formula implies that the volume of the nucleus is directly proportional to its mass number, and the density of nuclear matter is nearly constant for all nuclei.
5. If protons are all positively charged, why doesn't the nucleus fly apart due to electrostatic repulsion?
The nucleus is held together by the strong nuclear force, which is the most powerful of the four fundamental forces of nature. This force is much stronger than the electrostatic repulsion between protons, but it only acts over a very short range (on the scale of the nucleus itself). The strong nuclear force is charge-independent, meaning it acts equally between proton-proton, neutron-neutron, and proton-neutron pairs, effectively 'gluing' the nucleons together and ensuring the stability of the nucleus.
6. What is the connection between mass defect and the stability of a nucleus?
The mass defect (Δm) is the difference between the total mass of the individual, separate protons and neutrons and the actual measured mass of the nucleus. The actual mass is always slightly less. This 'missing' mass is converted into energy, known as the nuclear binding energy (E), according to Einstein's mass-energy equivalence principle, E = Δmc². This binding energy is what holds the nucleons together. Therefore, a larger mass defect signifies a greater binding energy, which in turn indicates a more stable nucleus.
7. What are nucleons, and what is the key information provided by the mass number (A)?
Nucleons is the collective term for the particles that constitute an atomic nucleus: the protons and neutrons. The mass number (A) of an atom is a crucial piece of information as it represents the total count of these nucleons in the nucleus. For example, in Uranium-238 (238U), the mass number 238 tells us that there are a total of 238 protons and neutrons combined in its nucleus.
