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Which four elements are the primary components of important biological molecules, such as proteins, fats, and carbohydrates?

nitrogen, carbon, hydrogen, and oxygen

Which of the following molecules is a compound?

sugar

Which of these refers to atoms with the same atomic number but different atomic masses?

isotopes

An atom and an ion of the same element differ in the number of _____.

electrons

A(n) _____ refers to two or more atoms held together by covalent bonds.

molecule

This atom can form up to _____ single covalent bond(s).

four

The innermost electron shell of an atom can hold up to _____ electrons.

two

Atoms with the same number of protons but with different electrical charges _____.

are different ions

An ionic bond involves _____.

an attraction between ions of opposite charge

How are ionic bonds formed?

one atom gives up an electron to a second atom

Each water molecule is joined to _____ other water molecules by ____ bonds.

four , hydrogen

The unequal sharing of electrons within a water molecule makes the water molecule _____.

polar

The pH of human blood is maintained at around pH 7.4. Why does a buffer system need to be present in blood to protect against changes in pH due to increases in acids?

The metabolic processes of the body produce more acids than bases.

Which of the following would be considered a trace element in the human body?

iron

Which of the following subatomic particles has appreciable mass and lacks a charge?

neutron

The number of protons in an uncharged atom _____.

equals the total number of electrons in the orbital shells

How do isotopes of an element differ?

by atomic mass number

For most atoms, a stable configuration of electrons is attained when the atom _____.

has 2 or 8 electrons in its outermost shell

A polar covalent bond _____.

is an unequal sharing of electrons

A hydrogen bond is _____.

weak

How are cohesion and surface tension related to the chemical properties of water?

All are properties related to hydrogen bonding.

A material that resists a change in pH is called a(n) _____.

buffer

Adding a base tends to _____ of a solution.

lower hydrogen ion concentration and increase the pH

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