Chapter 2 : atoms and molecules

An element is defined as a substance that:

• Is composed of more than one kind of atom

• Is held together by covalent bonds

• Cannot be broken into simpler substances by chemical reactions

• Cannot burn

• Is soluble in both acid and base

The particular type of element is determined by the number of:

• Electrons

• Protons

• Neutrons

• Valence electrons

• Energy levels

An atom has six protons and eight neutrons. It’s atomic mass is_____atomic mass units

• Two

• Four

• Six

• Eight

• Fourteen

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Chlorine has seven electrons in its valence shell. The number of electrons it just gain to complete its valence shell is:

• One

• Two

• Three

• Seven

• Eight

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• Carbonic acid

• Oxygen

• Water

• Sugar

• Carbon monoxide

When a chemical reaction is at equilibrium:

• The forward reaction is going faster

• The reverse reaction is going faster

• The forward and reverse reactions are proceeding at equal rates

• The forward reaction stops

• The reverse reaction stops

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A covalent bond is

• Forms only between identical atoms

• Involves the sharing of only one pair of electrons

• Is always polar

• May be polar or non polar depending on the satcoms involved

• Always forms between identical molecules

The covalent bond between a hydrogen atom and the oxygen atom in water is formed when:

• Hydrogen gains an electron from oxygen

• Hydrogen and oxygen share an electron pair

• Hydrogen and oxygen both lose an electron from their outer shells

• Hydrogen gains an electron from oxygen

• Hydrogen and oxygen both gain electrons in their outer shells

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The differences between an electrically neutral atom and an ion is that:

• An ion has an unequal number of protons and electrons, while an atom has an equal number

• An ion has an equal number of protons and electrons, while an atom has an unequal number

• An ion has an unequal number of protons and neutrons, while an ion has an equal number

• An atom has its electrons in orbitals, while an ion has its electrons in its nucleus

• An atom must have an equal number of neutrons and electrons, while an ion does not

• Water

• Iron

• Oxygen

• Rust

• Hydrogen