# Quiz - Structure and Bonding | Structure and Bonding

1

What is the electron configuration of bromine? (Z=35)

1s2 2p6 2s2 3d10 3p6 3s2 4f7

1s2 1p6 2s2 2p6 2d10 3s2 3p6 3d1

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5

1s2 2s2 2d6 3s2 3d6 4s2 3p10 4d5

s orbital: 2 electrons;   p orbital: 6 electrons;   d orbital: 10 electrons;   f orbital: 14 electrons
Energy of atomic orbitals: 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d …
Bromine (Z =35) ⇒ 35 electrons

2

What is the most stable calcium ion? (Calcium: Z=20)

Ca+

Ca2+

Ca-

Ca2-

Octet rule: atoms tend to form molecules in such a way as to reach an octet in the valence shell and attain a noble-gas configuration
Calcium (Z =20) ⇒ 20 electrons ⇒ 1s2 2s2 2p6 3s2 3p6 4s2
Nearest noble gas is Argon (1s2 2s2 2p6 3s2 3p6) ⇒ Ca needs to lose 2 electrons to get Ar's configuration

3

What is the most stable ionic compound formed by Sodium (Z=11) and Oxygen (Z=8)?

NaO

NaO2

Na2O2

Na2O

Sodium (Z = 11) ⇒ 1s2 2s2 2p6 3s1 ⇒ it needs to loose 1 electron to have the configuration of Neon ⇒ Na+
Oxygen (Z = 8) ⇒ 1s2 2s2 2p4 ⇒ it needs to gain 2 electrons to have the configuration of Neon ⇒ O2-
The most stable ionic compound formed by Na and O must be neutral ⇒ O2- + 2 Na+ (Na2​​​​​​​O)

4

Draw one of the resonance structures of SO3 without expansion of the valence shell. What is the formal charge of S?

– 1

0

+ 1

+ 2 Sulfur (Z = 16) ⇒ 1s2s2p3s3p4 = [Ne] 3s3p4
number of Valence Electrons (VE) in free atom = 6
number of VE in bound atom = 4 (4 covalent bonds)
Formal charge = 6 - 4 = +2

5

What is the geometry around the carbon atoms of C2Br4?

linear

trigonal planar

tetrahedral

pyramidal 3 neighboring electron domains around the carbon atoms (3 different atoms, 0 lone pair of electrons)
⇒ sp2 ​​​​​hybridization ⇒ trigonal planar

6

With regard to species ${}_{8}{}^{16}\mathrm{O}^{2-}$ and ${}_{10}{}^{20}\mathrm{Ne}$, which of the following statements is correct?

They have the same number of electrons

They have the same number of neutrons

They have the same number of protons

None of the above

${}_{8}{}^{16}\mathrm{O}^{2-}$ ⇒ 8 protons, 8 neutrons, 10 electrons
​​​​​​​${}_{10}{}^{20}\mathrm{Ne}$ ⇒ 10 protons, 10 neutrons, 10 electrons