Structure of the Atom — Science STD 9 — Question

In a sample of ethyl ethanoate (CH₃COOC₂H₂), the two oxygen atoms have the same number of electrons but different number of neutrons. Which of the following is the correct reason for it?

1. One of the oxygen atoms has gained electrons.
2. One of the oxygen atoms has gained protons.
3. The two oxygen atoms are isotopes.
4. The two oxygen atoms are isobars.

You are provided with a mixture of petroleum and water. You can separate this mixture by_____?

This subatomic particle of an atom has a POSITIVE charge.

The molecular weight of calcium carbonate CaCO_3​ is:

A particle X has 17 protons, 18 neutrons and 18 electrons. This particle is most likely to be:

The mass of single atom of an element X is 2.65 × 10^-23g. The atomic mass and name of element is:

The electrons revolve around the nucleus only in certain fixed paths called:

The number of Al³⁺ ions in 0.051g of aluminium oxide are (Atomic mass of Al = 27u, O = 16u).

The atomic number of an element X is 8 and that of element Y is 4. Both these elements can exhibit a valency of:

“Is malleable and ductile” best describes:

1. A solution.
2. A metal.
3. A compound.
4. A non-metal.