Atomic Structure and Mass

The up quark is the lightest quark with mass ~2.2 MeV/c^2, followed closely by the down quark at ~4.7 MeV/c^2. All other quarks (charm, strange, top, bottom) are significantly heavier. Option C correctly identifies both light quarks.

1 atomic mass unit (amu) equals 931.5 MeV/c² in energy units, which is approximately 931 × 10^5 eV/c². This conversion is fundamental in nuclear physics for calculating mass-energy equivalence.

Avogadro's number (6.022 × 10²³) is the number of particles (atoms, molecules, or ions) in one mole of a substance. This fundamental constant in chemistry relates atomic mass to molar mass.

The atomic number of an element equals the number of protons in its nucleus. Fluorine has 9 protons, so its atomic number is 9. The number of neutrons (10) is irrelevant to determining atomic number, and 19 (total nucleons) would be the mass number, not atomic number. 90 has no relation to fluorine's properties.

The atomic number specifically indicates the number of protons in an atom's nucleus. This number defines the element and determines its position in the periodic table. Atomic mass includes both protons and neutrons, while atomic charge is the net electrical charge (protons minus electrons).

A mole is defined as exactly 6.022 × 10²³ particles (Avogadro's number). This count is independent of the substance - one mole of any element contains the same number of atoms, whether it's light helium atoms or heavy lead atoms. The difference is in mass, not particle count.

The atomic number is defined as the number of protons in the nucleus of an atom. This number uniquely identifies an element. It is not the number of electrons (which can vary in ions), neutrons (which vary in isotopes), or the sum of protons and neutrons (which is the mass number).

Adding or removing electrons creates ions - charged atoms. Changing electrons does not create isotopes (involves neutrons), change the element (determined by protons), or directly affect atomic mass (dominated by nucleons).

An oxygen atom has an atomic mass of approximately 16 atomic mass units (amu), while a hydrogen atom has an atomic mass of about 1 amu. Therefore, an oxygen atom is approximately 16 times more massive than a hydrogen atom.

The atomic mass of oxygen is 16 atomic mass units, while hydrogen has an atomic mass of 1. This means an oxygen atom is exactly 16 times heavier than a hydrogen atom.

Beta decay involves a neutron converting to a proton (emitting an electron and antineutrino). This increases the atomic number by 1 (more protons) but mass number stays nearly the same (proton+neutron count unchanged). Option A describes neither decay type. Option C describes alpha decay. Option D is incorrect.

Helium is the second most abundant element in the Sun, accounting for approximately 24% of the Sun's mass (about 8% by number of atoms). While hydrogen makes up 74% by mass, helium produced through nuclear fusion in the Sun's core gradually accumulates. The remaining 2% consists of heavier elements including oxygen, carbon, neon, and iron, which were present in the molecular cloud from which the Sun formed.

The sum of protons and neutrons in an atom's nucleus is called the atomic mass number or mass number. This number represents approximately the atom's total mass since protons and neutrons each have about 1 atomic mass unit. Atomic number refers only to protons, while P/N factor and 'big number' are not scientific terms.

In an atom, the atomic number equals the number of protons. Mass number equals protons + neutrons. For element F with atomic number 9 and mass number 19: protons = 9, neutrons = 19-9 = 10. Option C is correct.