Chemical Bonding and Lewis Structures

A set of 40 question-and-answer flashcards covering ionic and covalent bonding, electronegativity, Lewis structures, common bonding patterns, and octet-rule exceptions.

What is a chemical bond?

A lasting interaction between atoms, ions, or molecules that enables the formation of chemical compounds.

What causes an ionic bond to form?

Electrostatic attraction between oppositely charged ions (cations and anions).

What do we call an atom that has gained extra electrons and carries a negative charge?

An anion.

What do we call an atom that has lost electrons and carries a positive charge?

A cation.

Why do salts dissolve readily in water?

Water molecules dissociate the individual cations and anions, overcoming the ionic attraction.

Why does sodium form a positive ion in NaCl?

It easily donates its single outer-shell electron, leaving a net positive charge.

Why does chlorine form a negative ion in NaCl?

It strongly accepts an extra electron to complete its outer shell, gaining a net negative charge.

In a covalent bond, how are electrons handled?

They are shared between the outer orbitals of two atoms.

How many shared electron pairs make up a single covalent bond?

One shared pair.

How many shared electron pairs make up a double covalent bond?

Two shared pairs.

How many shared electron pairs make up a triple covalent bond?

Three shared pairs.

Convert 1 ångström (Å) to nanometres (nm).

1 Å = 0.1 nm.

What is electronegativity?

The tendency of an atom or functional group to attract electrons toward itself.

What characterizes a nonpolar covalent bond?

The atoms share electrons evenly, with little or no electronegativity difference.

Give an example of a nonpolar covalent bond.

H–H or Cl–Cl.

What characterizes a polar covalent bond?

One atom attracts the shared electrons more strongly than the other due to higher electronegativity.

How does electronegativity difference relate to bond polarity?

The greater the electronegativity difference, the more polar the bond.

How many valence electrons does oxygen have?

Six.

How many valence electrons does hydrogen have?

One.

What molecule results when two hydrogens and one oxygen bond to complete an octet?

H₂O (water).

In structural theory, how many bonds does a tetravalent atom like carbon usually form?

Four bonds.

How many bonds does nitrogen generally form?

Three bonds.

How many bonds does oxygen generally form?

Two bonds.

How many bonds do hydrogen and halides generally form?

One bond.

What is the first step when drawing a Lewis diagram?

Count and add the total number of valence electrons contributed by all atoms.

What does the octet rule state for period 2 and 3 elements (excluding hydrogen)?

They strive to have eight electrons in their valence shell; hydrogen seeks two.

According to Lewis rules, how is a single bond represented?

As one pair of shared electrons, often drawn as a line.

Why is hydrogen always shown as singly bonded in Lewis structures?

Because it can hold only two electrons.

What do we call electrons that are not involved in bonding and are shown as pairs in Lewis structures?

Lone pairs (non-bonded electron pairs).

After drawing bonds in H₂O, how many valence electrons remain to be placed as lone pairs?

Four electrons.

How many total valence electrons are counted for NH₃ when drawing its Lewis structure?

Eight electrons (5 from N + 3 from H).

What must the final Lewis structure satisfy besides the octet rule?

It must contain exactly the correct number of valence electrons counted initially.

In Lewis structures, what guides the choice of the skeletal arrangement of atoms?

Determining the central atom and attaching other atoms before assigning remaining electrons.

Which group of elements commonly form incomplete octets?

Group 3 elements, especially boron and aluminium.

Why can boron form only three bonds in many compounds?

It has three unpaired electrons after promotion and often retains an incomplete octet.

Why is boron’s electron promotion energetically favourable?

The small energy gap between its 2s and 2p orbitals is offset by the energy released when additional bonds form.

What electron configuration change allows carbon to form four bonds?

Promotion of one 2s electron to an empty 2p orbital, giving four unpaired electrons.

What is the key force that holds ions together in a salt crystal?

Strong electrostatic attraction (ionic bonding).

What term describes the variation of covalent bonds into polar or nonpolar types?

Bond polarity; covalent bonds can be polar or nonpolar depending on electronegativity difference.

How does water’s Lewis structure illustrate the octet rule for oxygen?

Oxygen shares two pairs with H atoms and retains two lone pairs, reaching eight valence electrons.