# Quiz - Structure and Bonding | Structure and Bonding

1

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

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)

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)?

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+ (Na2O)

4

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

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?

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?

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