Structure of Atom-2

An element has the symbol ²³⁵X.

⁹²

What does the number 235 represent?

• The mass in gram of the atom.

• The number of protons in the atom.

• The number of neutrons in the atom.

• The total number of protons and neutrons in the atom.

The boiling point of pentane is 36^oC. Which of the following statements is true about the molecules of pentane at 40^oC?

• The pentane molecules become lighter.

• The kinetic energy of the pentane molecules is lower.

• The distance between pentane molecules increases.

• The attraction force of the pentane molecules becomes stronger.

Four balloons are filled with four different gases.

Which balloon will decrease in size most slowly?

• A

• B

• C

• D

Which of the following statements is true about butane molecules when it is cooled to a temperature of –140^oC?

(Melting point of butane is –138^oC and its boiling point is –1^oC).

• The butane molecules remain static.

• The butane molecules move randomly.

• The butane molecules are arranged closely together.

• The distance between the butane molecules increases.

Which of the following particles contain 10 electrons, 11 protons and 12 neutrons?

• ¹⁹F^-

  ⁹

• ²⁰Ne

  10

• ²³Na⁺

  ¹¹

• ²⁴Mg²⁺

  ¹²

An element ⁷₃X has

• three valence electrons

• a positively charged ion.

• 3 protons and 7 neutrons.

• is located in Group 17 of the Periodic Table.

• W and Z

• X and Y

• V and Y

• V and X

Which of the following graphs shows the temperature (T) against time (t) when a mixture of pentane (boiling point 36^oC) and hexane (boiling point 70^oC) is distilled?

• 
• 
• 
• 

Nitrogen monoxide (NO) and propane (C₂H₆) diffuse at the same rate at room conditions because

• they are both gases.

• they are both denser than air.

• they do not react with each other.

• they have the same molecular mass.

• A

• B

• C

• D