Chemistry Lecture Exam Iii

Front 1

Periodic law

Back 1

When arranged by atomic mass, the elements exhibit a periodic recurrence of similar properties.

Front 2

Dmitri Mendeleev

Back 2

Arranged the elements into a periodic table (1870).

Front 3

How are the elements now arranged?

Back 3

The elements are now arranged in order of atomic number (number of protons) rather than atomic mass (based on the work of Moseley who found a direct dependence between an element's nuclear charge and its position in the periodic table).

Front 4

Quantum numbers (n)

Back 4

n=size (energy); n=1, 2, 3...

Front 5

Quantum number (l)

Back 5

l=shape; 0 to n-1

Front 6

Quantum number (mL)

Back 6

mL=orientation; -L to 0 to +L

Front 7

Quantum number (mS)

Back 7

mS=spin; +½ or -½

Front 8

Pauli exclusion principle

Back 8

No two electrons in the same atom can have the same four quantum numbers.

Example:
H; Z=1: n=1, l=0, mL=0, mS= +½
He; Z=2: n=1, l=0, mL=0, mS= -½

Because the spin quantum number can only have can have only two values, an atomic orbital can hold a maximum of two electrons and they must have opposing spins.

Front 9

Hund's rule

Back 9

When orbitals of equal energy are available, the electron configuration of the lowest energy has the maximum number of unpaired electrons with parallel spins.

Front 10

Elements of the same group

Back 10

Elements within a group have similar chemical properties because they have similar outer electron configurations.

Front 11

Ionization energy

Back 11

Energy required to remove an electron. Increases up a group and across a period from left to right.

Front 12

Electron affinity

Back 12

Energy required to add an electron. Increases up a group and across a period from left to right (with many exceptions).

Front 13

Atomic size

Back 13

Increases down a group and across a period from right to left. The larger the atom, the less attracted its electrons are to the nucleus. The less attracted an electron is to a nucleus, the more likely it is to be given up by an atom. Therefore, a smaller atom that is highly attracted to its electrons is more likely to add an electron and become more stable as it reaches a noble gas electron configuration than a larger atom that is less attracted to its electrons.

Front 14

Why do atoms bond?

Back 14

Bonding lowers the potential energy between positive and negative particles.

Front 15

Ionic bonding

Back 15

-Occurs when metal atoms transfer electrons to nonmetal atoms, and the results ions attract each other and form an ionic solid.
-Typically observed between atoms with large differences in their tendencies to lose or gain electrons.
-Electron transfer from nonmetal to metal occurs and each atom forms an ion with a noble gas electron configuration.
-The total number of electrons lost by the metal atoms equals the total number of electrons gained by the nonmetal atoms.

Front 16

Lattice energy

Back 16

Increases up a group and across a period from left to right. Increases as charge increases.

Front 17

Electronegativity

Back 17

Increases up a group and across a period from left to right. Fluorine is the most electronegative element.

Front 18

Covalent bonding

Back 18

-Occurs between nonmetal atoms and usually results in molecules.
-The bonded atoms share a pair of electrons which remain localized between them.
-We typically observe electron sharing when two atoms with a small difference in their tendencies to lose or gain electrons.
-Each atom in a covalent bond achieves a full outer (valence) level of electrons. Each atom in a covalent bond “counts” the shared electrons as belonging entirely to itself.

Front 19

Single bond

Back 19

bond order=1

Front 20

Double bond

Back 20

Bond order=2

Front 21

Triple bond

Back 21

Bond order=3

Front 22

Metallic bonding

Back 22

Occurs when many metal atoms pool their electrons in a delocalized electron “sea” that holds all the atoms together.

Front 23

Lewis electron-dot symbol

Back 23

The Lewis electron-dot symbol of an atom depicts the number of valence electrons for a main-group element.

Front 24

Octet rule

Back 24

In bonding, many atoms lose, gain, or share electrons to attain a filled outer level or eight or two.