Chemistry Basics Quiz

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Questions and Answers

What is the relative mass of a proton compared to an electron?

1/1840

1840

1 (correct)

Which of the following statements about isotopes is TRUE?

Isotopes have different numbers of protons.

Isotopes are defined by their varying charges.

Isotopes have identical physical properties.

Isotopes have the same number of protons but different numbers of neutrons. (correct)

What information does the atomic number provide about an atom?

The number of electrons in the atom.

The total number of neutrons in the atom.

The number of protons in the nucleus. (correct)

The mass of the atom.

What is the primary function of a time of flight mass spectrometer?

To identify elements and measure isotopes present in a sample. Signup and view all the answers

How are neutrons calculated within an atom?

Mass number - Atomic number. Signup and view all the answers

What represents the second ionisation energy?

The enthalpy change when one mole of singly charged gaseous ions forms doubly charged gaseous ions Signup and view all the answers

Which factor affects ionisation energy by increasing the attraction between the nucleus and electrons?

The number of protons in the nucleus Signup and view all the answers

Why are successive ionisation energies always larger?

The remaining electrons experience a stronger attraction due to the positive ion formed Signup and view all the answers

What happens during the ionisation process described in the equation Ti+ (g) → Ti2+(g) + e-?

One mole of gaseous Ti+ is converted into Ti2+ ions Signup and view all the answers

What does shielding refer to in the context of ionisation energy?

The blocking of attraction by inner shell electrons Signup and view all the answers

Which statement about ionisation energies is true?

Elements with larger atoms generally have lower ionisation energies Signup and view all the answers

What significant jump in ionisation energy is typically observed?

Between the last outer electron and an inner shell electron Signup and view all the answers

Which of the following best explains the trend in ionisation energies across a period?

Attraction between electrons and nucleus increases Signup and view all the answers

What occurs to first ionisation energy as you move down a group in the periodic table?

It decreases due to increased distance from the nucleus and shielding. Signup and view all the answers

Why does sodium have a much lower first ionisation energy compared to neon?

Sodium's outer electron is in a shell further from the nucleus. Signup and view all the answers

What is the primary reason for the increase in first ionisation energy across a period?

The number of protons increases, enhancing nuclear attraction. Signup and view all the answers

What happens to the first ionisation energy when moving from magnesium to aluminum?

It decreases slightly because aluminum begins filling the 3p subshell. Signup and view all the answers

Why is there a small drop in first ionisation energy from phosphorus to sulfur?

Sulfur's 3p subshell has paired electrons in an orbital. Signup and view all the answers

How does the concept of shielding affect the first ionisation energy down a group?

Increased shielding reduces the attraction between outer electrons and the nucleus. Signup and view all the answers

Which element would likely have the highest first ionisation energy?

Neon (Ne) Signup and view all the answers

What is the effect of increasing nuclear charge without a corresponding increase in shielding across a period?

Increased ionisation energy. Signup and view all the answers

What happens to MH+ ions as the solvent evaporates?

They move towards a negative plate. Signup and view all the answers

In an electric field, how does the mass of a particle affect its velocity?

Lighter particles have a faster velocity. Signup and view all the answers

What distinguishes ions in the flight tube?

Their m/z values and flight times. Signup and view all the answers

What does the current generated in the detector indicate?

The abundance of the species. Signup and view all the answers

What is the mass-to-charge ratio (m/z) of 24Mg2+?

12 Signup and view all the answers

Which equation represents the relationship between kinetic energy, mass, and velocity?

KE = ½ mv^2 Signup and view all the answers

Given ions have the same kinetic energy, which will move faster?

Ions with smaller m/z values. Signup and view all the answers

How long would an ion of 59Ni+ take to travel along a flight tube that is 0.8000 m long if accelerated to 1.000 x 10-16 J of kinetic energy?

It cannot be determined without mass. Signup and view all the answers

What is the percentage abundance of the isotope 63-Cu?

72.5% Signup and view all the answers

Which of the following isotopes of chlorine has a higher percentage abundance?

Cl35 Signup and view all the answers

What is the relative abundance contribution for the 160 m/z peak in the bromine mass spectrum?

It is due to both Br79-Br81 and Br81-Br79 Signup and view all the answers

When using a mass spectrometer, what typically happens to the molecules during the ionization stage?

They break up and create fragments Signup and view all the answers

How does the abundance of Br79 compare to that of Br81?

Both have equal abundance at 50% Signup and view all the answers

What percentage abundance does the isotope 65-Cu have?

27.5% Signup and view all the answers

What is the significance of including mass spectrometers in planetary space probes?

To identify elements and their isotopes on other planets Signup and view all the answers

What equation is used to calculate the weighted average of the isotopes in copper?

63.5 = yx63 + (1-y)x65 Signup and view all the answers

Study Notes

Atomic Structure

Three fundamental sub-atomic particles:
- Proton: located in the nucleus, relative mass of 1, charge of +1
- Neutron: located in the nucleus, relative mass of 1, charge of 0
- Electron: located in orbitals, relative mass of 1/1840, charge of -1
Lithium (Li) represents an atom with a mass number of 7 and an atomic number of 3.
Atomic number (Z) indicates the number of protons; mass number (A) equals the total count of protons and neutrons (A = Z + N).

Isotopes

Isotopes are variants of elements with the same proton count but different neutron counts.
Isotopes exhibit similar chemical properties due to identical electronic structures but can have varying physical properties due to different masses.
Mass spectrometers determine isotopes in a sample regardless of ionization tendencies.

Ionization Energy

Second ionization energy: enthalpy change for forming one mole of gaseous ions with a single positive charge into one mole of gaseous ions with a double positive charge, exemplified by the reaction Ti+(g) → Ti2+(g) + e-.
Factors influencing ionization energy:
- Nuclear attraction: More protons enhance attraction.
- Electron distance: Outer electrons further from the nucleus experience weaker attraction.
- Shielding effect: Electrons in inner shells reduce nuclear attraction felt by outer electrons.

Successive Ionization Energies

Patterns in successive ionization energies reveal electronic structure insights.
Each successive ionization energy is larger due to increased effective nuclear attraction after each electron is removed.
Significant jumps in ionization energy, such as between the fourth and fifth electrons, suggest that subsequent electrons reside in closer inner shells, raising attraction to the nucleus.

Trends in Ionization Energies

Ionization energies decrease down a group due to increased shielding and distance from the nucleus.
Ionization energies increase across a period as protons increase, enhancing nuclear attraction while maintaining the same shielding effect.
Sodium (Na) has lower ionization energy than neon (Ne) due to lower nuclear attraction on its outer electron being further from the nucleus and more shielded.

Mass Spectrometry

Acceleration stage: positive ions accelerated by an electric field to a constant kinetic energy; lighter ions travel faster than heavier ions.
Flight tube: ions distinguished by flight time, with lighter ions moving faster than heavier ones.
Detection: ions generate current upon reaching the detector; current size correlates with species abundance.

Example Calculations

For nickel isotope analysis:
- Example isotope: 59Ni; kinetic energy of ions is 1.000 x 10^-16 J, flight tube length is 0.8000 m.
- Example calculations yield abundance percentages for isotopes of copper (Cu): 72.5% for ^63Cu and 27.5% for ^65Cu.

Mass Spectra

Chlorine isotopes: Cl35 (75%) and Cl37 (25%).
Bromine isotopes: Br79 (50%) and Br81 (50%).
Mass spectra diagrams illustrate relative abundances and molecular fragments from electron impact ionization, leading to distinct peaks in the spectrum.

Applications of Mass Spectrometry

Mass spectrometers deployed in space probes identify elemental compositions on other planets that may differ in isotopic abundances from Earth.

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Description

Test your knowledge on fundamental chemistry concepts such as the relative masses of protons and electrons, isotopes, atomic numbers, and mass spectrometry. This quiz will challenge your understanding of atomic structure and measurement techniques.