Chemistry Review over Covalent Bonding
What are the properties of a covalently bonded substance?
-Low melting point -Gas or liquid at room temperature (may also be a soft solid) -Cannot conduct electricity -Either soluble or soluble in water
What does the saying "like dissolves like" mean?
-Nonpolar molecules will dissolve in other nonpolar substances due to their similar structure. -Polar molecules will dissolve in other polar molecules due to the force of attraction between the positive end of one polar molecule and negative end of another polar molecule. -Simply put, the like poles dissolve together, but nonpolar molecules cannot dissolve with polar molecules due to their differences.
A diatomic molecule...
...consists of two atoms of the same element covalently bonded together.
How many types of diatomic molecules are there? What are they?
7 types; H₂, N₂, O₂, Cl₂, Br₂ I₂, F₂ (Have no fear of [the] Browns in Cleveland)
Two elements, when bonded, are stable with less than eight electrons in the outer level. Which two elements exhibit this behavior?
Boron and beryllium.
What is the octet rule, and why is hydrogen an exception to it?
Elements are stable when they have 8 electrons in the outer level. Hydrogen is an exception because it only needs 2 electrons in the outer level due to the fact that it only has one energy level.
What are the numerical prefixes used in naming covalent molecules?
Mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, deca-.
Covalently bonded molecules consist of a nonmetal bonded to a ________.
Nonmetal, watch for the pattern here!
Rank the three types of covalent bonds (single, double, triple) in order of increasing length.
Single> Double> Triple
If a substance does not dissolve in water, what conclusion can be drawn about the substance?
That it must be nonpolar.
Some elements, when bonded, exhibit an expanded octet. What does this mean?
They may have more than 8 electrons in the outer level. This happens when elements have at least 3 energy levels and an unoccupied d sublevel.
Rank the three types of covalent bonds (single, double, triple) in order of increasing strength.
Triple> Double> Single
A double covalent bond occurs when two atoms share ____ electrons, or ___ pairs of them.
four; two
Compounds that contain covalent bonds have ___ melting points.
low
A covalent bond in which the electrons are shared equally is classified as ________.
nonpolar
A molecule is considered nonpolar if the bonds are ________ or if the polar bonds are arranged _____________.
nonpolar; symmetrically
Is water polar or nonpolar?
polar
A covalent bond occurs when atoms _____ electrons.
share
A triple covalent bond occurs when two atoms share ___ electrons, or _____ pairs of them.
six; three
A single covalent bond occurs when two atoms share ___ electrons, or ___ pair of them.
two; one
