Atomic Structure and Mass

Isotopes are atoms of the same element (same number of protons) that have different numbers of neutrons, resulting in different atomic masses. Carbon-12 and Carbon-14 are classic examples. 'Isotropes' (B), 'Isolates' (C), and 'Isomates' (D) are not valid scientific terms.

The atomic mass of Hydrogen is approximately 1, while the atomic mass of Oxygen is approximately 16. Therefore, an oxygen atom is roughly 16 times more massive than a hydrogen atom. This ratio is fundamental to the calculation of molecular weights.

The electron has a rest mass of approximately 9.109 × 10^-31 kilograms or 0.511 MeV/c². This is one of the fundamental constants of physics and is crucial in atomic and nuclear physics. The mass is incredibly small, which is why electrons can easily move and form electric currents. Option A correctly represents this value, while other options have either wrong coefficients, wrong signs, or wrong exponents.

Oxygen has atomic mass approximately 16 amu while hydrogen has atomic mass approximately 1 amu. Therefore, an oxygen atom is 16 times heavier than a hydrogen atom.

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons, resulting in different atomic masses. For example, carbon-12 and carbon-14 are both carbon isotopes with different masses. This is a fundamental concept in nuclear chemistry.

The number of protons (atomic number) uniquely defines each element. Neutrons vary among isotopes, electrons change in ions, and ions are charged particles, not element identifiers.

A mole is defined as the amount of substance containing exactly 6.022 x 10^23 elementary entities (atoms, molecules, ions, etc.). This number is called Avogadro's number and serves as a bridge between the atomic scale and macroscopic measurements. It allows chemists to count particles by weighing them.

A hydrogen atom has approximately 1 atomic mass unit (amu), while an oxygen atom has approximately 16 amu. This ratio of 16:1 means oxygen is 16 times more massive than hydrogen.

The four most abundant elements in the universe by mass are hydrogen (~74%), helium (~24%), oxygen (~1%), and carbon (~0.5%). This makes carbon the fourth most abundant. Hydrogen is first, not fourth.

The atomic mass of helium is approximately 4 atomic mass units (amu), so one mole (Avogadro's number) of helium atoms has a mass of about 4 grams. This is a direct application of the mole concept: molar mass in grams equals atomic mass in amu.

It is the number of neutrons present in element, i.e. 15 - 7 = 8. 

For an element that exists as isotope, the mass of the element is calculated as the weighted average of all naturally occurring isotopes of that element. The average mass is calculated in decimals.

Isobars have different atomic numbers. They do not have the same number of protons that of an element.

In a silica molecule there are one silicon atom and two oxygen atoms. So total atoms = three

[Chemical Formula of silica = SiO₂ ]