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Which gas is present in the atmosphere in the greatest amount?

• Oxygen

• Nitrogen

• Carbon dioxide

• Methane

Which gas makes up approximately 21% of the atmosphere?

• Argon

• Carbon

• Oxygen

• Water vapor

Approximately what percentage of the air is carbon dioxide?

• 4 %

• 1%

• 3.50 %

• 0.04 %

What is the study of the composition and chemical properties of substance?

• Biology

• Genetics

• Science

• Chemistry

The information shows the number of proton and nucleon number in an atom X.

Number of protons = 13 Number of nucleon = 14

Which of the following symbols represents the atom X?

• 14
  X
  13

• 27
  X
  14

• 27
  X
  13

• 13
  X
  14

If the valence shell electronic structure of a neutral atom of an element is 7, the element will belong to the group of

• alkali metals

• halogens.

• alkaline earth metals.

• noble gas.

What is a substance consisting of two or more elements that is chemically combined together?

• element

• mixture

• compound

• isotope

Which statement is correct?

• Na is more reactive than Li

• Rb is more reactive than K

• Li is less reactive than Na

• All of the statements are correct.

Which of the following terms would best classify a sample of pure sodium chloride?

• An element

• A highly reactive metal

• A poisonous gas

• A compound

How many electrons are being shared between the two carbon atoms in the compound ethyne?      
 Ethyne has the structure: H $-$  C $\equiv$  C $-$  H

• 1

• 2

• 3

• 6