Which represents a p orbital?

C

Which is correct for the line emission spectrum for hydrogen?

A. Line M has a higher energy than line N. 
B. Line N has a lower frequency than line M. 
C. Line M has a longer wavelength than line N. 
D. Lines converge at lower energy.

C

What is the ground state electron configuration of an atom of chromium, Cr (Z = 24)?

A. [Ar]3d⁶

B. [Ar]4s²3d⁴

C. [Ar]4s¹3d⁵

D. [Ar]4s²4p⁴

C

A large number of the candidates had ground state configuration of Cr as 4s² 3d⁴ rather than 4s¹ 3d⁵

Which electron transition emits radiation of the longest wavelength?

C

Which represents the shape of an s atomic orbital?

A

Which is correct for ${}_{16}^{34}{\text{S}}^{2-}$?

D

A well answered question. 88 % of the candidates deduced the correct numbers of protons, neutrons and electrons in the sulfide ion.

What is the condensed electron configuration of the Fe²⁺ ion? 

A. [Ar]3d⁶
B. [Ar]3d⁴4s²
C. [Ar]3d⁵4s¹
D. [Ar]3d⁶4s²

A

What is the number of protons and the number of neutrons in ¹³¹I?

A

What is represented by A in ${}_{\text{Z}}^{\text{A}}{\text{X}}^{2-}$?

A. Number of electrons

B. Number of neutrons

C. Number of nucleons

D. Number of protons

C

Naturally occurring gallium consists of the isotopes ⁷¹Ga and ⁶⁹Ga. What is the approximate percentage abundance of ⁶⁹Ga?

M_r(Ga) = 69.72.

A.  40 %

B.  50 %

C.  60 %

D.  75 %

C

Which technique is used to detect the isotopes of an element?

A.  Mass spectrometry

B.  Infrared spectroscopy

C.  Titration

D.  Recrystallization

A

What is the relative molecular mass of bromine, according to the following mass spectrum?

NIST Mass Spectrometry Data Center Collection © 2014 copyright by the U.S. Secretary of Commerce
on behalf of the United States of America. All rights reserved.

A.  $\frac{158\times 52+160\times 100+162\times 48}{52+100+48}$

B.  $\frac{158\times 52+160\times 100+162\times 48}{158+160+162}$

C.  $\frac{79\times 11+81\times 11+158\times 52+160\times 100+162\times 48}{11+11+52+100+48}$

D.  $\frac{79\times 11+81\times 11}{11+11}$

A

Which is the electron configuration of a chromium atom in the ground state?

A. [Ne]3s²3p⁶4s¹3d⁴

B. [Ar]3d³

C. 1s²2s²2p⁶3s²3p⁶4s²3d⁴

D. [Ar]4s¹3d⁵

D

What is the maximum number of electrons that can occupy the 4th main energy level in an atom?

A.  $8$

B.  $14$

C.  $18$

D.  $32$

D

Poorly answered questions from candidates in general. Only 38% of candidates could state the maximum number of electrons in the 4th principal energy level is 32, with the most common incorrect answer being 18.

Which statements are correct for the emission spectrum of hydrogen?

I. The lines converge at higher frequencies.

II. Electron transitions to n = 2 are responsible for lines in the visible region.

III. Lines are produced when electrons move from lower to higher energy levels.

A.   I and II only

B.   I and III only

C.   II and III only

D.   I, II and III

A

In which set do all the species contain more electrons than neutrons?

A.     ¹⁴N, ¹⁶O, ¹¹C

B.     ¹⁴N, ¹⁶O, ¹¹C^4–

C.     ¹⁴N^3–, ¹⁶O^2–, ¹¹C

D.     ¹⁴N^3–, ¹⁶O^2–, ¹¹C⁴⁺

C

What is the relative atomic mass, $A_{\mathrm{r}}$, of an element with this mass spectrum?

A.  $24.0$

B.  $24.3$

C.  $24.9$

D.  $25.0$

B

Well answered question with more than 70% of candidates able to find the RAM of an element from isotope relative abundances.

Which are correct statements about the emission spectrum of hydrogen in the visible region?

I.     The red line has a lower energy than the blue line.

II.     The lines converge at longer wavelength.

III.     The frequency of the blue line is greater than the frequency of the red line.

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

B

Which of the following is the electron configuration of a metallic element?

A.  [Ne] 3s² 3p²

B.  [Ne] 3s² 3p⁴

C.  [Ne] 3s² 3p⁶ 3d³ 4s²

D.  [Ne] 3s² 3p⁶ 3d¹⁰ 4s² 4p⁵

C

Bromine consists of two stable isotopes that exist in approximately a 1 : 1 ratio. The relative atomic mass, A_r, of bromine is 79.90. Which are the stable isotopes of bromine?

A. ⁷⁹Br and ⁸¹Br

B. ⁸⁰Br and ⁸¹Br

C. ⁷⁸Br and ⁸⁰Br

D. ⁷⁹Br and ⁸⁰Br

A

Almost 56 % of candidates could find a 1:1 ratio as an average of 2 items, however many had ⁷⁹Br and ⁸⁰Br with an average mass of 79.90

What does ${}_{12}^{24}M{g}^{2+}$ represent?

A.     An ion with 12 protons and 24 neutrons

B.     An ion with 14 protons and 24 neutrons

C.     An ion with 12 protons and 12 neutrons

D.     An ion with 12 protons and 22 neutrons

C

Which statement about ⁵⁶Fe³⁺ and ⁵⁴Fe²⁺ is correct?

A. Both have the same numbers of protons and electrons.

B. Both have the same number of protons.

C. Both have the same number of neutrons.

D. Both have the same numbers of protons and neutrons.

B

The full electron configuration of an element is:

1s²2s²2p⁶3s²3p²

To which group and period does the element belong?

D

What is the relative atomic mass of an element with the following mass spectrum?

A.  23

B.  24

C.  25

D.  28

B

69% of the candidates determined the relative atomic mass of the element from its mass spectrum.

How are emission spectra formed?

A.  Photons are absorbed when promoted electrons return to a lower energy level.

B.  Photons are absorbed when electrons are promoted to a higher energy level.

C.  Photons are emitted when electrons are promoted to a higher energy level.

D.  Photons are emitted when promoted electrons return to a lower energy level.

D

What is represented by ^“2−” in ${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X}^{2-}$?

A.  loss of electron

B.  gain of electron

C.  loss of proton

D.  gain of proton

B

Which experimental results support the theory that electrons exist in discrete energy levels?

A.  ¹H NMR

B.  X-ray diffraction pattern

C.  Emission spectra

D.  IR spectra

C

A well answered question. 84% of the candidates identified emission spectra as the experimental results that support the theory that electrons exist in discrete energy levels.

What is the composition of the nucleus of ²⁶Mg?

D

How many p-orbitals are occupied in a phosphorus atom?

A.  2

B.  3

C.  5

D.  6

D

Which electron transition in the hydrogen atom emission spectrum emits radiation with the longest wavelength?

A.     n = 2 → n = 1

B.     n = 1 → n = 2

C.     n = 4 → n = 1

D.     n = 3 → n = 2

D

What is the maximum number of electrons that can occupy a p-orbital?

A.  2

B.  3

C.  6

D.  8

A

Question 6 was poorly answered as it asked for the number of electrons in a p orbital. Very few students gave the correct answer of 2. The majority chose answer C (6) for the maximum number of electrons that can occupy a p-orbital, rather than A (2). It appears candidates reflexively conflated p-orbitals with the entire p subshell in any given period.

Which transition in the hydrogen atom emits visible light?

A. n = 1 to n = 2

B. n = 2 to n = 3

C. n = 2 to n = 1

D. n = 3 to n = 2

D

This question discriminated well between high scoring and low scoring candidates. 68% of the candidates chose the correct transition that emits visible light (n = 3 to n = 2). The most commonly chosen distractor C was the only other option that involved emission.

Which shows the number of subatomic particles in ³¹P³⁻?

A