Nuclear and Atomic Physics

Positron is the odd one out because it's antimatter, while the other three are particles found in ordinary matter. Electrons, protons, and neutrons are the main subatomic particles that make up atoms. A positron is the antimatter counterpart of an electron with the same mass but opposite charge.

The nuclei of atoms that make up a newborn baby (excluding hydrogen) were indeed created in ancient stars through stellar nucleosynthesis. Most elements heavier than hydrogen and helium were formed in the cores of stars that exploded billions of years ago. These atoms were then recycled through the universe and eventually became part of our solar system and our bodies.

If one neutron is added to a helium nucleus (which has 2 protons and 2 neutrons), you get Helium-5, which is unstable and quickly decays back to helium by emitting a neutron. However, the question asks what the 'result' is - in terms of elemental identity, adding a neutron doesn't change the element. The element remains helium, as the number of protons (which defines the element) is unchanged.

The atomic number defines an element. Oxygen has 8 protons, so removing 2 leaves 6 protons - which is carbon. The number of protons in the nucleus determines what element an atom is.

Isotones are atoms of different elements that have the same number of neutrons in their nuclei. This differs from isotopes (same protons, different neutrons) and isobars (same mass number but different proton/neutron counts).

Nuclear sizes are extremely small (on the order of 10^-15 m). The fermi (fm) is the standard unit for nuclear dimensions - 1 fermi = 10^-15 meters. Angstrom (10^-10 m) is too large for nuclei, while newton and tesla measure force and magnetic field respectively.

Isotopes are atoms of the same element with identical atomic numbers (same protons) but different mass numbers (different neutrons). This variation in neutrons changes atomic mass while preserving chemical identity.

Nuclear sizes are on the order of 10⁻¹⁵ meters, measured in fermis (also called femtometers). A typical nucleus has a diameter of 3-15 fermis, making this the appropriate unit for nuclear dimensions, unlike angstroms used for atomic scales.

Atomic mass will be affected as it depends on sum of protons and neutrons in an atom.

Most of the alpha rays went undeflected through the gold foil. It could be possible only when positively charged protons occupy very small space in atom.

Rutherford's model stated that electrons revolve around the nucleus in well defined orbits. According to this, the atom should have been unstable. An electron being charged particle in accelerated motion would radiate energy and would collapse onto the nucleus within a very small fraction of time owing to the electrostatic pull of the nucleus. It could not explain the stability of an atom.

Hydrogen atom does not have any neutron.

Most of X-rays in Rutherford's experiment went undeflected, which concludes that most of the space inside an atom is empty.

Rutherford’s alpha scattering experiment lead to the discovery of the nucleus and that all positive charge of an atom is concentrated in the nucleus.