Atomic Structure and Isotopes Quiz
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Questions and Answers

What is the primary function of the mass spectrometer?

  • To calculate the density of an element
  • To analyze the chemical reactivity of compounds
  • To determine the isotopes present in a sample (correct)
  • To measure the temperature of a sample

In isotopes, what remains constant among them?

  • Number of electrons
  • Mass number
  • Number of neutrons
  • Number of protons (correct)

Which technique is NOT used for ionization in a mass spectrometer?

  • Chemical vapor deposition (correct)
  • Electron impact
  • Ion drift
  • Electro spray ionization

What is the correct relationship for calculating the number of neutrons in an atom?

<p>Number of neutrons = Mass number - Atomic number (D)</p> Signup and view all the answers

What happens during the electron impact ionization process?

<p>Electrons from an electron gun knock out outer electrons (C)</p> Signup and view all the answers

What primarily causes the increase in first ionisation energy across a period?

<p>The effective attraction of the nucleus increases due to more protons. (C)</p> Signup and view all the answers

Why does sodium (Na) have a lower first ionisation energy than neon (Ne)?

<p>Na's outer electron is in a higher energy level shell. (A)</p> Signup and view all the answers

Which characteristic is true for heavier ions in a mass spectrometer?

<p>They have a longer drift time than lighter ions (A)</p> Signup and view all the answers

What accounts for the small drop in first ionisation energy from magnesium (Mg) to aluminium (Al)?

<p>3p electrons are higher in energy and more shielded. (B)</p> Signup and view all the answers

What is a defining feature of electro spray ionization?

<p>It is ideal for larger organic molecules and avoids fragmentation (D)</p> Signup and view all the answers

What is the reason for the drop from phosphorus (P) to sulfur (S) in first ionisation energy?

<p>The fourth 3p electron experiences repulsion from other electrons. (A)</p> Signup and view all the answers

In an atom of Lithium (Li), what is the mass number?

<p>7 (B)</p> Signup and view all the answers

Which of the following accurately describes the trend in second ionisation energy across periods?

<p>It displays a similar pattern but shifted one to the left. (C)</p> Signup and view all the answers

What is unique about lithium's second ionisation energy compared to helium's?

<p>Lithium's second electron is removed from the 1s shell with no shielding. (B)</p> Signup and view all the answers

Which factor does NOT contribute to the trend of ionisation energy across a period?

<p>Increased electron shielding. (C)</p> Signup and view all the answers

What is meant by periodicity in the context of ionisation energy?

<p>The repeating pattern of ionisation energy across periods. (D)</p> Signup and view all the answers

What effect does increasing the mass of a particle have on its velocity, given constant kinetic energy?

<p>Velocity decreases (A)</p> Signup and view all the answers

How is the time of flight for an ion in a mass spectrometer determined?

<p>By its velocity and the length of the flight tube (B)</p> Signup and view all the answers

What is the relationship between the size of the current generated by ions at the detector and their abundance?

<p>Directly proportional (B)</p> Signup and view all the answers

When calculating relative atomic mass, what factors must be included in the equation?

<p>Isotopic mass and abundance (A)</p> Signup and view all the answers

What happens during electron impact ionization in a mass spectrometer?

<p>It breaks the molecules into fragments (C)</p> Signup and view all the answers

When using electro spray ionization in a mass spectrometer, what is observed?

<p>Only the molecular ion peak is detected (C)</p> Signup and view all the answers

What is the m/z value for a 2+ ion of 24Mg?

<p>12 (B)</p> Signup and view all the answers

How do mass spectrometers assist in identifying elements on other planets?

<p>By determining the isotopic composition (B)</p> Signup and view all the answers

What is the significance of the molecular ion peak in mass spectrometry?

<p>It corresponds to the relative atomic mass of the molecule (B)</p> Signup and view all the answers

In the calculation of relative atomic mass, what needs to be done when using relative abundance instead of percentage abundance?

<p>Use the same equation with different values (D)</p> Signup and view all the answers

During the mass spectrum analysis of Cl2, which isotopes are involved?

<p>Cl35 and Cl37 (B)</p> Signup and view all the answers

What assumption can be made about ions with smaller m/z values in a flight tube?

<p>They achieve the same energy but have higher velocities (B)</p> Signup and view all the answers

What is a key feature of the Bohr model of the atom?

<p>Electrons are arranged in shells (D)</p> Signup and view all the answers

Which combination of isotopes would yield an average atomic mass of approximately 63.5 for copper?

<p>75% of 63Cu and 25% of 65Cu (B)</p> Signup and view all the answers

Which of the following correctly describes the filling order of sublevels in an atom?

<p>1s → 2s → 2p → 3s → 3p → 4s → 3d (C)</p> Signup and view all the answers

What is the electronic configuration of a calcium atom?

<p>1s2 2s2 2p6 3s2 3p6 4s2 (B)</p> Signup and view all the answers

Which subshell is filled first for d-block elements when they form ions?

<p>4s before 3d (C)</p> Signup and view all the answers

What is the correct definition of first ionisation energy?

<p>Energy change when one mole of gaseous atoms forms gaseous ions (B)</p> Signup and view all the answers

Which factor does NOT affect the first ionisation energy?

<p>Mass of the atom (C)</p> Signup and view all the answers

Which statement is true regarding successive ionisation energies?

<p>Successive ionisation energies generally increase (D)</p> Signup and view all the answers

What electronic structure corresponds to the ion Mg2+?

<p>1s2 2s2 2p6 (C)</p> Signup and view all the answers

Why does helium have a higher first ionisation energy than hydrogen?

<p>It has its first electron in the first shell with no shielding (D)</p> Signup and view all the answers

Which of the following ions has a configuration of [Ar] 4s03d10?

<p>Zn2+ (C)</p> Signup and view all the answers

In which group of the periodic table is an element with a large jump between its 2nd and 3rd ionisation energies likely to be found?

<p>Group 2 (B)</p> Signup and view all the answers

Which element displays an electronic configuration of 1s22s22p63s23p6 4s13d5?

<p>Chromium (B)</p> Signup and view all the answers

What is the ionisation energy trend as you move down a group in the periodic table?

<p>Decreases due to increased shielding (A)</p> Signup and view all the answers

When filling orbitals within the same sublevel, according to Hund's rule, how should electrons be placed?

<p>Fill each orbital singly before pairing up electrons (D)</p> Signup and view all the answers

What shape do p sublevels have?

<p>Dumbbell (B)</p> Signup and view all the answers

What is the electronic configuration of an oxygen ion (O2-)?

<p>1s2 2s2 2p6 (B)</p> Signup and view all the answers

Flashcards

Atomic number (Z)

The number of protons in an atom's nucleus.

Mass number (A)

The total number of protons and neutrons in an atom's nucleus.

Isotopes

Atoms of the same element with the same number of protons but different numbers of neutrons.

Electron impact ionization

A technique used to ionize a sample using high-energy electrons to knock out an outer electron, forming positive ions.

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Electrospray ionization

A technique for ionizing larger organic molecules by dissolving the sample in solvent and creating a mist, allowing the molecules to gain a proton.

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Mass spectrometer

A tool used to identify and measure the isotopes in a sample of an element.

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Ionization (Mass Spec)

The process of converting neutral sample particles into charged ions in a mass spectrometer.

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time of flight mass spectrometry

A technique used in mass spectrometry to measure the time it takes ions to travel through a drift tube, allowing the determination of their mass.

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s sublevels

S sublevels are spherical in shape and represent a type of atomic orbital containing a maximum of two electrons.

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p sublevels

P sublevels are shaped like dumbbells with two lobes, representing atomic orbitals with a maximum of six electrons.

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Electronic configuration

A description of the arrangement of electrons in an atom's different energy levels and sublevels.

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Subshell filling order

Atoms fill subshells in order of increasing energy, and the 3d subshell is higher in energy than the 4s

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1s2

Describes the lowest energy level (n=1) with the 's' sublevel containing two electrons.

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2p4

Describes the second energy level (n=2) with the 'p' sublevel containing four electrons.

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s block element

An element whose outermost electron is filling an 's' sublevel, like sodium with 1s2 2s2 2p6 3s1.

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p block element

An element whose outermost electron is filling a 'p' sublevel, like chlorine with 1s2 2s2 2p6 3s2 3p5.

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d block element

An element whose outermost electron is filling a 'd' sublevel, like vanadium with 1s2 2s2 2p6 3s2 3p6 4s2 3d3.

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Positive ion formation

When atoms lose electrons from their outermost shell, forming ions with a positive charge.

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Negative ion formation

When atoms gain electrons in their outermost shell, forming ions with a negative charge.

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Ionization energy

The minimum energy required to remove one electron from a gaseous atom.

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First ionization energy

The energy required to remove one electron from a neutral atom in the gaseous phase (to form a 1+ ion)

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Successive ionization energies

The energy required to remove each successive electron from the atom, each ionization energy is higher than the last.

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Factors affecting ionization energy

Three main factors: nuclear charge, distance of electrons from the nucleus, and shielding of the nucleus.

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Kinetic Energy (KE)

The energy an object possesses due to its motion.

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How does mass affect velocity for ions with the same KE?

Lighter ions move faster than heavier ions if they have the same kinetic energy.

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What is the drift area in a mass spectrometer?

The region where ions travel through a flight tube, separated based on their mass-to-charge ratio.

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Time of Flight (t)

The time it takes for an ion to travel the length of the flight tube in a mass spectrometer.

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How do you calculate the time of flight?

Time of flight (t) is calculated by dividing the distance (d) by the velocity (v) of the ion.

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What is the relationship between m/z and time of flight?

Ions with a smaller m/z value travel faster and have a shorter time of flight compared to ions with a larger m/z value.

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How does the detector work in a mass spectrometer?

The detector measures the current generated when ions hit it, proportional to their abundance.

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What is m/z?

The mass-to-charge ratio of an ion, a unique identifier in a mass spectrometer.

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How does the abundance of a species get measured?

The abundance of a species is measured by the size of the current produced by the ions in the detector.

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What is the relative atomic mass (R.A.M.)?

The weighted average of the masses of all isotopes of an element, taking into account their abundance.

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How can you calculate R.A.M. using percentage abundance?

R.A.M. is calculated by summing the products of the isotopic mass multiplied by its percentage abundance and dividing by 100.

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What is the parent ion or molecular ion?

The peak in a mass spectrum corresponding to the complete molecule without any fragmentation.

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How does a mass spectrometer analyze molecules?

It breaks down molecules into fragments and measures the m/z of each fragment, providing information about the molecule's structure.

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What is the difference between parent and MH+ ion?

The parent ion corresponds to the neutral molecule, while MH+ ion is the protonated molecule formed using electrospray ionization.

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What are the advantages of electrospray ionization?

Electrospray ionization minimizes fragmentation of large molecules and allows the determination of their molecular mass with high accuracy.

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Ionization Energy Trend Across a Period

Generally increases across a period due to increasing nuclear charge (more protons) with a constant shielding effect, making it harder to remove an electron.

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Why Na has Lower Ionization Energy than Ne

Sodium's outermost electron is in a higher energy level further from the nucleus and shielded by inner electrons, making it easier to remove than the tightly held electrons in neon.

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Small Drop in Ionization Energy from Mg to Al

Aluminum's outer electron is in a slightly higher energy 3p subshell, which is shielded by the 3s electrons, making it easier to remove than magnesium's 3s outer electrons.

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Periodicity

Repeating patterns in the properties of elements across a period, like the trend of increasing ionization energy.

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Why is there a small drop from P to S?

Sulfur's 4th 3p electron experiences repulsion from the other electron already in the 3p orbital, making it slightly easier to remove than phosphorus's 3rd 3p electron.

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Second Ionization Energy Pattern

The trend of second ionization energy across a period is similar to the first ionization energy, but shifted one element to the left. Group 1 elements now have the highest second ionization energies.

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Lithium's High Second Ionization Energy

Lithium has a high second ionization energy because the second electron is removed from the 1s shell, which is closer to the nucleus and less shielded.

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Factors Influencing Ionization Energy

Three key factors affect an element's ionization energy: nuclear charge, electron shielding, and energy level of the electron being removed.

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Study Notes

Atomic Structure

  • Subatomic Particles: Atoms have three fundamental particles:
    • Protons: Located in the nucleus, with a relative mass of 1 and a relative charge of +1.
    • Neutrons: Located in the nucleus, with a relative mass of 1 and a relative charge of 0.
    • Electrons: Located in orbitals, with a relative mass of 1/1840 and a relative charge of -1.

Atomic Representation

  • Lithium (Li) Example: The representation ⁷Li₃ shows:
    • Atomic number (Z): 3 (number of protons).
    • Mass number (A): 7 (total number of protons and neutrons).
    • Number of neutrons: Calculated as A - Z = 7 - 3 = 4

Isotopes

  • Definition: Atoms of the same element with the same number of protons but different numbers of neutrons are called isotopes.
  • Chemical properties: Isotopes have similar chemical properties due to the same electronic structure.
  • Physical properties: Isotopes may have slightly differing physical properties due to their varying masses.

Mass Spectrometry

  • Purpose: Used to identify and quantify isotopes in a sample.

  • Conditions: Must be under vacuum to avoid interference from air particles.

  • Steps:

    • Ionisation: Sample is converted into ions (e.g., electron impact, electrospray ionisation). Electron impact is best for smaller molecules, while electrospray is preferred for larger organic molecules.
    • Acceleration: Positive ions are accelerated to a constant kinetic energy by an electric field.
      • Lighter ions accelerate faster.
      • Heavier ions accelerate slower.
    • Flight Tube: Ions travel through a tube where their flight time differs based on mass-to-charge ratio (m/z). Lighter ions move faster.
    • Detection: Ions reach a detector generating a current proportional to abundance.

  • Time of Flight (TOF) Calculations: Time taken for an ion to travel through the flight tube depends on its velocity and the length of the tube. The velocity in turn depends on the ion's mass, ensuring that heavier ions take longer to travel.

    • The mass-to-charge ratio (m/z) is determined for each isotope.
    • Relative atomic mass(RAM) calculation is based on the percentage abundance of isotopes.

Calculating Relative Atomic Mass (RAM)

  • Formula: RAM = ∑ (isotopic mass × % abundance) / 100
  • Variations: can be used if relative abundance is used instead of percentage abundance.
  • Examples of calculations provided.

Mass Spectra for Diatomic Molecules

  • Diatomic molecules: Examples for Cl₂and Br₂show that peaks are created due to different isotope combinations.

Electronic Structure

  • Models: Early Bohr models, modern models consider principal energy levels(numbered 1,2,3..),
    • sub-energy levels labeled s , p, d, and f
    • s holds up to 2 electrons
    • p holds up to 6 electrons
    • d holds up to 10 electrons
    • f holds up to 14 electron
  • Filling Order: Electrons fill orbitals in order of increasing energy. (Example 3d is higher in energy than 4s) Specific filling order: 1s → 2s →2p → 3s → 3p → 4s → 3d → 4p and so on.)
  • Orbital Shapes: s orbitals are spherical, p orbitals are dumbbell-shaped, etc.
  • Electronic Configuration: Writing electronic arrangements using numbers and letters.
    • Example for oxygen: 1s²2s²2p⁴

Electronic Structure of Ions

  • Positive Ions: Electrons are lost from the outermost shell.
  • Negative Ions: Electrons are gained.

Ionization Energies

  • Definition: First ionization energy is the energy required to remove one mole of electrons from one mole of gaseous atoms.

  • Factors: Affecting ionization energy include:

    • Nuclear attraction: Stronger with more protons.
    • Electron distance: Greater distance, weaker attraction.
    • Shielding: Inner electrons repel outer electrons, reducing attraction.

  • Successive Ionization Energies: Energies required to remove successive electrons increase due to increased nuclear attraction on remaining electrons.

  • Patterns: -Increases across a period due to increasing nuclear attraction. -Decreases down a group due to increasing distance from the nucleus and shielding. -Specific drops in the graph, due to additional influencing factors, are explained in detail.

  • Groups 1 and 2: These patterns in successive ionization energies give information about the element's electronic structure.

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Test your knowledge on atomic structure, including subatomic particles, atomic representation, and isotopes. Understand the differences between protons, neutrons, and electrons, and explore how isotopes affect chemical and physical properties.

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