Chemistry · Some Basic Concepts Of Chemistry · NEET
Yes, in almost every case. An atom is the smallest unit of an element. A molecule is built by joining atoms, so it is usually bigger and heavier. For example, one hydrogen atom (H) is smaller than a hydrogen molecule (H2), which is two H atoms bonded together. The only special case is a monatomic molecule (like a helium atom, He), where the atom and the molecule are the same single particle.
Most atoms do not like to stay alone because they are not stable by themselves. So they join to form molecules (like H2, O2) or ionic solids (like NaCl). But noble gas atoms (He, Ne, Ar) are already stable, so they exist as single free atoms. For these, one atom is also counted as one molecule (monatomic molecule).
It depends on how it is written. 'O' means one oxygen atom. 'O2' means one oxygen molecule, which is two oxygen atoms bonded together. The oxygen gas you breathe is O2 (a molecule). This matters in NEET because when you count particles, you must know whether the question means atoms or molecules.
One water molecule (H2O) has 3 atoms: two hydrogen atoms and one oxygen atom. So if you have 1 mole of water molecules (6.022 x 10^23 molecules), the number of atoms is 3 times that. This is exactly the kind of counting NEET tests.
An element is a pure substance made of only one kind of atom (like the element oxygen). An atom is the single smallest particle of that element. A molecule is two or more atoms joined by bonds. So: element is the substance, atom is its smallest particle, and molecule is a group of atoms bonded together.
Because O2 contains two atoms joined by a chemical bond. An atom is a single particle with no bonds inside it. The moment two or more atoms bond, the new particle is called a molecule. O2 is a homoatomic molecule because both atoms are the same element.
No. A homoatomic molecule has the same kind of atoms (like O2, N2, H2, O3). A heteroatomic molecule has different kinds of atoms (like H2O, CO2, HCl). Both are still molecules because they are atoms joined by bonds.
The number of hydrogen atoms present in 5.4 g of urea is (molar mass of urea = 60 g mol^-1; NA = 6.022 x 10^23 mol^-1)
Among the following, choose the ones with an equal number of atoms. A. 212 g of Na2CO3 (molar mass 106). B. 248 g of Na2O (molar mass 62). C. 240 g of NaOH (molar mass 40). D. 12 g of H2 (molar mass 2). E. 220 g of CO2 (molar mass 44).
Try the real previous-year questions from this chapter — each with the answer and a full solution.
An atom is the smallest particle of an element. A molecule is two or more atoms joined by chemical bonds. So a molecule is made of atoms.
Yes. Helium exists as single stable atoms, so one He atom counts as one monatomic molecule. This is a special case.
Atoms: H, O, Na (single particles). Molecules: H2, O2, H2O (atoms bonded together). Note H and H2 are different: one is an atom, the other is a molecule.
Many NEET mole questions ask for the number of ATOMS, not molecules. If you forget to multiply by atoms per molecule, you get the wrong answer. It appears almost every year.
Atomicity is the number of atoms in one molecule of an element. He = 1 (monatomic), O2 = 2 (diatomic), O3 = 3 (triatomic), P4 = 4 (tetratomic).
