Mass Spectra

Review and preview of Atomic structure

Multiple Choice

The nucleus of a ²³Na atom contains

• 11 protons and 12 neutrons.

• 11 protons and 12 electrons.

• 23 protons and 11 neutrons.

• 11 protons and 11 electrons.

Multiple Choice

The mass spectrum for a sample of a metal is shown below.

The relative atomic mass of the metal is

• 63.2

• 63.4

• 63.6

• 64.0

Multiple Choice

Chlorine has two isotopes with relative isotopic mass 35 and 37. Four m/z values are given below. Which will occur in a mass spectrum of chlorine gas, Cl₂, from an ion with a single positive charge?

• 35.5

• 36

• 71

• 72

Multiple Choice

Bromine has two isotopes with relative isotopic masses 79 and 81. Which of the following values for mass/charge ratio could correspond to a peak in the mass spectrum of bromine, Br₂? You should assume the ions detected have a single positive charge.

• 79.9

• 80

• 159

• 160

Multiple Choice

Which of these statements is incorrect?

• The atomic radius of metals increases down a Group.

• The trend in the melting temperature of successive elements across Period 2 is similar to that in Period 3.

• A metallic structure is held together by attractions between metal atoms and delocalized electrons.

• Na⁺ and O^2– ions are isoelectronic.

Multiple Choice

In which of the following series does the melting temperature of the element increase from left to right?

• Li, Na, K

• Al, Si, P

• Si, P, S

• Na, Mg, Al

Multiple Choice

The correct sequence for the processes that occur in a mass spectrometer is

• vaporization, ionization, acceleration, deflection and detection.

• vaporization, acceleration, ionization, deflection and detection.

• ionization, vaporization, acceleration, deflection and detection.

• ionization, vaporization, deflection, acceleration and detection.

Multiple Choice

Which of the following ions would be deflected most in a mass spectrometer?

• ³⁵Cl⁺

• ³⁷Cl⁺

• ³⁷Cl²⁺

• (³⁵Cl – ³⁷Cl)⁺

Multiple Choice

The chemical properties of an element are determined by its

• electronic structure

• number of neutrons.

• relative atomic mass

• number of protons plus neutrons.

Multiple Choice

In a mass spectrometer, positive ions are accelerated by

• bombarding them with fast–moving electrons.

• bombarding them with fast–moving protons.

• passing them between charged plates.

• passing them through a magnetic field.

Multiple Choice

Bromine has two isotopes with relative isotopic masses 79 and 81. Which of the following values for mass/charge ratio could correspond to a peak in the mass spectrum of bromine, Br₂? You should assume the ions detected have a single positive charge.

• 79.9

• 80

• 159

• 160

Multiple Choice

Which pair of ions is isoelectronic?

• Ca²⁺ and O^2–

• Na⁺ and O^2–

• Li⁺ and Cl^–

• Mg²⁺ and Cl^–

Electronic Structure of the atom

• The electronic structure of an atom that determines its chemical properties.

• Aufbau Principle: Electrons can be regarded as having certain energy levels. The lower levels fill before the higher levels are occupied.

Electronic Configuration

• The shells used in the simple view of the atom are divided into subshells. 

• Shells are also called the principal quantum number of electrons. 

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The higher the energy of the shell, the more subshells it contains.

Orbitals in subshells

• An orbital has no edge, the surface which would contain a given percentage (say, 95%) of the electron density

• Each electron in an atom is different from all the other electrons

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s subshell

• s-orbitals can contain a maximum of two electrons. 

• These have the same energy value, but are said to have opposite spin values (Pauli exclusion principle)

• The s-orbital is always spherically symmetrical

• Total number of electrons in 1s orbital = ____

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p subshell

• There are three p orbitals, each of which can contain a maximum of two electrons. 

• Total number of electrons in 2p orbitals = _______

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