Atoms and Molecules — Science STD 9 — Question

The number of electrons in an element X is 15 and the number of neutrons is 16. Which of the following is the correct representation of the element?

When a body moves with a constant speed along a circle, then which of the following is correct : 

Intercalated disc is present in:

1. Striated muscle.
2. Smooth muscle.
3. Cardiac muscle.
4. Both b and c.

A group of cells alike in form, function and origin are called __________.

Which of the following statement is true:

Which of the following contribute to green house effect?

1. Methane (CH₄).
2. Carbon dioxide (CO₂).
3. Chlorofluorocarbons (CFCs).
4. All of these.

Kharif crop is:

The atomic number of an element E is 16. The number of electrons in ion E^2- will be:

1. 16
2. 18
3. 15
4. 14

Elements X, Y, and Z have atomic numbers 6, 9, and 12 respectively. Which one has four electrons in its valence shell?

Which of the following does not lose their nucleus at maturity?