The brilliant red colors seen in fireworks are due to the emission of light with wavelengths around 650 nm when strontium salts such as Sr(NO3)2 and SrCO3 are heated. Calculate the frequency of red light of wavelength 6.50 × 102 nm.λ = 650 nm = 6.50 x 10-7 m

ν = c = 2.9979 x 108 m/s = 4.61 x 1014 Hz λ 6.50 x 10-7 m

The blue color in fireworks is often achieved by heating copper(I) chloride (CuCl) to about 1200°C. Then the compound emits blue light having a wavelength of 450 nm. What is the increment of energy (the quantum) that is emitted at 4.50 × 102 nm by CuCl?λ = 450 nm = 4.50 x 10-7 m

Ephoton = hc = (6.626 x 10-34 Js)(2.9979 x 108 m/s) λ 4.50 x 10-7 m

= 4.417 x 10-19 J

Calculate the energy required to excite the hydrogen electron from level n = 1 to level n = 2. Also calculate the wavelength of light that must be absorbed by a hydrogen atom in its ground state to reach this excited state.E = -2.178 x 10-18 J(Z2/n2)for H, Z = 1 so E = -2.178 x 10-18 J(1/n2)From n = 1 to n = 2ΔE = -2.178 x 10-18 J( - ) = -2.178 x 10-18 J( - ) = 1.634 x 10-18 J

λ = hc = (6.626 x 10-34 Js)(2.9979 x 108 m/s) Ephoton 1.634 x 10-18 J

= 1.217 x 10-7 m

Calculate the energy required to remove the electron from a hydrogen atom in its ground state.

E = -2.178 x 10-18 J(Z2/n2)for H, Z = 1 so E = -2.178 x 10-18 J(1/n2)

From n = 1 to n = ∞ since the electron is being removed

ΔE = -2.178 x 10-18 J( - ) = -2.178 x 10-18 J( - ) = -2.178 x 10-18 J( - ) = 2.178 x 10-18 J

For principal quantum level n = 5, determine the number of allowed subshells (different values of ℓ), and give the designation of each.

EXERCISE 5 ELECTRON SUBSHELLS

n = 5 so l = 0, 1, 2, 3, 4 or s, p, d, f, and then gl = 0 5sl = 1 5pl = 2 5dl = 3 5fl = 4 5g (theoretical, not actually observed)

Give the full electron configuration and orbital diagram for each of the following elements.Sulfur Iron

Lithium Aluminum

Magnesium Silicon

EXERCISE 6

1s22s22p63s23p4

1s22s1

1s22s22p63s2

1s22s22p63s23p64s23d6

1s22s22p63s23p1

1s22s22p63s23p2

Orbital Diagram—Sulfur

EXERCISE 6 CONTINUED

1s 2s 2p 3s 3p

Orbital Diagram—Lithium

EXERCISE 6 CONTINUED

1s 2s

Orbital Diagram—Magnesium

EXERCISE 6 CONTINUED

1s 2s 2p 3s

Orbital Diagram—Iron

EXERCISE 6 CONTINUED

1s 2s 2p 3s 3p

4s 3d

Orbital Diagram—Aluminum

EXERCISE 6 CONTINUED

1s 2s 2p 3s 3p

Orbital Diagram—Silicon

EXERCISE 6 CONTINUED

1s 2s 2p 3s 3p

Write the noble gas configuration for the following ions.S2-

 Al3+

 Mg2+

EXERCISE 6 CONTINUED—OTHER SIDE OF PAGE

A sulfide ion has two more electrons than a sulfur atom. S2- [Ne]3s23p6 isoelectronic with argon, Cl-, P3-, K+, Ca2+

[He]2s22p6 isoelectronic with neon, Mg2+, Na+, F-, O2-, N3-

[He]2s22p6 isoelectronic with neon, Al3+, Na+, F-, O2-, N3-

Write the noble gas configuration for the following ions.

 Fe3+

 Br-

EXERCISE 6 CONTINUED—OTHER SIDE OF PAGE

[Ar]3d5

Electrons are lost from 4s first

[Ar]4s24p6

Isoelectronic with Kr, Se2-, As3-, Rb+, Sr2+

Determine the number of unpaired electrons in each element from Exercise 6.

EXERCISE 7

Orbital Diagram—Sulfur

EXERCISE 7

1s 2s 2p 3s 3p

Orbital Diagram—Lithium

EXERCISE 7

1s 2s

Orbital Diagram—Magnesium

EXERCISE 7

1s 2s 2p 3s

No unpaired electrons

Orbital Diagram—Iron

EXERCISE 7

1s 2s 2p 3s 3p

4s 3d

Orbital Diagram—Aluminum

EXERCISE 7

1s 2s 2p 3s 3p

Orbital Diagram—Silicon

EXERCISE 7

1s 2s 2p 3s 3p

The fi rst ionization energy for phosphorus is 1060 kJ/mol, and the fi rst ionization energy for sulfur is 1005 kJ/mol. Why?

P

S

EXERCISE 8 TRENDS IN IONIZATION ENERGIES

First IE = removing “last” electronFor phosphorous, this means removing the electron that makes the 3p subshell half-full. A filled OR half-filled subshell is stable; the atom does not “want” to lose this stability.For sulfur, removing the last electron results in a half-filled 3p subshell. Since stability is gained, the first IE is lower for sulfur than for phosphorous.

Consider atoms with the following electron configurations:a. 1s22s22p6

b. 1s22s22p63s1

c. 1s22s22p63s2

Identify each atom. Which atom has the largest first ionization energy, and which one has the smallest second ionization energy? Explain your choices.

EXERCISE 9 IONIZATION ENERGIES

Neon Sodiu

mMagnesium

Largest first IE (noble gas, stable)

Smallest second IE because it gains a noble gas configuration when it loses 2 electrons

Predict the trend in radius for the following ions: Be2+, Mg2+, Ca2+, and Sr2+. Explain the trend as well.

EXERCISE 10 TRENDS IN RADII

Be2+ < Mg2+ < Ca2+ < Sr2+

Beryllium has the smallest number of principal energy levels, so it is the smallest. As the number of principal energy levels (n) increases, the size of the atom increases.