Q: Calculate the effective nuclear charge ($$Z_{\text{eff}}) $$experienced by a 2s electron in a magnesium atom ($$Z=12). $$Use the equation $$Z_{\text{eff}} = Z - S$$ and assume $$S=2$$ for the 2s electron.

$$Z_{\text{eff}} = 12 - 2 = 10$$

Question 1

Which of the following best explains why tin (IV) oxide (SnO$$_2) $$exists, based on the electron configuration of tin?

Accepted Answer

Tin can lose four electrons from its 5p and 5s orbitals, achieving a noble gas configuration.

Question 2

Calculate the effective nuclear charge ($$Z_{	ext{eff}}) $$experienced by a 2s electron in a magnesium atom ($$Z=12). $$Use the equation $$Z_{	ext{eff}} = Z - S$$ and assume $$S=2$$ for the 2s electron.

Accepted Answer

$$Z_{	ext{eff}} = 12 - 2 = 10$$

Question 3

Arrange the following elements in order of increasing atomic radius: Ba, Ca, Na.

Accepted Answer

Na \u003c Ca \u003c Ba

Question 4

Which of the following ions is the smallest in size: S$$^{2-}$$, Cl$$^-$$, or K$$^+$$? All have the same number of electrons.

Accepted Answer

K$$^+$$

Question 5

What is the trend in first ionization energy as you move down Group 1A (alkali metals) in the periodic table?

Accepted Answer

It decreases because the atomic radius increases, making it easier to remove an electron.

Question 6

Which of the following molecules exhibits resonance and what is the bond order between the central atom and oxygen in that molecule?

Accepted Answer

CO$$_3$$^{2-}$$; bond order = $$\frac{4}{3}$$

Question 7

Which of the following bonds is the most polar?

Accepted Answer

Li–Cl

Question 8

Which step in the Born-Haber cycle for KF(s) formation corresponds to the lattice energy?

Accepted Answer

Step 5

Question 9

Given the following values, calculate the lattice energy of KF(s):

Sublimation of K(s) to K(g): 89.24 kJ
Bond dissociation of ½ F$$_2(g$$): 79.4 kJ
1st Ionization energy of K(g): 419 kJ
1st Electron affinity of F(g): -332.6 kJ
Enthalpy of formation of KF(s): -562.6 kJ

Use the equation:

$$	ext{Lattice Energy} = 	ext{Step 1} + 	ext{Step 2} + 	ext{Step 3} + 	ext{Step 4} - 	ext{Step 6}$$

Accepted Answer

$$89.24 + 79.4 + 419 + (-332.6) - (-562.6) = 818 kJ$$

Question 10

Which of the following molecules is T-shaped according to VSEPR theory?

Accepted Answer

IF$$_3$$

Question 11

What is the most likely X–A–X bond angle in a molecule AX$$_2$$ where A has one lone pair and two bonds to X?

Accepted Answer

107°

Question 12

Which two orbitals interact to form the N–H bonds in NH$$_3$$ according to valence bond theory?

Accepted Answer

N sp$$^3$$ and H 1s

Question 13

Which of the following statements is FALSE?

Accepted Answer

Strong covalent bonds have strong atom attraction, but small orbital overlap.

Question 14

Which of the following compounds has the largest lattice energy?

Accepted Answer

Al$$_2O$_3$$

Question 15

Which of the following best describes why electron affinity is typically a negative (exothermic) value?

Accepted Answer

Energy is released when an electron is added to a neutral atom, stabilizing the atom.

Question 16

Which of the following pairs will possess the more negative electron affinity and why?

S or Cl?

Accepted Answer

Cl, because it is more electronegative and closer to a full octet.

Question 17

Which of the following is the correct Lewis dot symbol for phosphorus (P)?

Accepted Answer

P with five dots around it

Question 18

Which of the following best explains why Fe$$^{3+} is $$smaller than Fe$$^{2+}$$?

Accepted Answer

Fe$$^{3+}$$ has lost an additional electron, increasing the effective nuclear charge and pulling electrons closer.

Question 19

Which of the following molecules is predicted to be polar and have a bent molecular geometry?

Accepted Answer

H$$_2O$$

Question 20

Which of the following best describes the hybridization of the central atom in BF$$_3$$?

Accepted Answer

sp$$^2$$

Chem 1210 Midterm 4 Study Guide: Periodic Properties, Bonding, and Molecular Geometry

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