Unit 1 HL Chemistry: Asteroid mining, atomic structure and moles - Flashcards

Flashcards covering key concepts from Lesson 1–4 (and related topics) including element/compound distinctions, electron configuration, spectra and isotopes, ionization energy, moles, empirical formulas, and spectroscopy of stars and Mars.

What are the three main categories of matter described in Lesson 1 (element or compound) and how are they defined?

Elements cannot be chemically broken down into simpler substances; compounds are formed when atoms of different elements are chemically bonded in fixed ratios; mixtures contain more than one substance in no fixed ratio and can be separated by physical methods.

From which property can the electron configuration of an atom be deduced (as taught in Lesson 2)?

The atomic number.

How are colour, wavelength, frequency, and energy related across the electromagnetic spectrum?

Shorter wavelengths correspond to higher frequencies and higher energy; longer wavelengths correspond to lower frequencies and lower energy.

What information do mass spectra provide about elements (as used to study Mars)?

Mass spectra give the relative atomic masses from isotopic composition and allow interpretation of the identity and abundance of isotopes.

What is relative atomic mass (Ar) and how is it determined?

Ar is the weighted average mass of an element’s atoms relative to 1/12 of carbon-12; it is unitless and calculated from isotopic masses and their abundances: Ar = sum(abundance × isotope mass) / sum of abundances.

Why might Ar values change over time?

New measurements and data can alter the weighted average; IUPAC revises Ar values as data improves; radioactive decay can influence abundances.

What defines an isotope and how do isotopes differ in physical properties?

Isotopes have the same number of protons (and electrons) but different numbers of neutrons; they have different masses and densities, though chemical properties are similar.

What causes the lines in an emission spectrum?

Electrons transition between fixed energy levels and emit photons with specific energies, producing discrete spectral lines.

What are Lyman, Balmer, and Paschen series in the hydrogen emission spectrum?

Series of lines for electron transitions to n=1 (Lyman, UV), n=2 (Balmer, visible), and n=3 (Paschen, infrared).

What is the convergence limit in the hydrogen emission spectrum and what does it represent?

The point where lines converge as n → ∞; it represents the first ionization energy of hydrogen.

How do you calculate the first ionization energy from spectral data?

Energy per photon is E = hc/λ; to get energy per mole, multiply by Avogadro’s number: E_mol = (hc/λ) × NA (units: kJ/mol).

What is a mole and how many particles does it contain?

A mole contains 6.02 × 10^23 particles (atoms, molecules, etc.).

How do you convert mass to moles using molar mass?

Moles = mass / molar mass (M); the molar mass is the mass of one mole of a substance.

How do you determine the empirical formula from percent composition?

Convert each element’s mass to moles, divide by the smallest number of moles to get a whole-number ratio, then write the empirical formula (e.g., Na2S2O3 from Na 29.1%, S 40.5%, O 30.4%).

Why is reflux used in empirical formula experiments (e.g., tin iodide)?

To heat reaction mixtures for extended periods without losing volatile reactants/solvents; a condenser prevents loss of components.

How can spectra help identify elements present in stars (or stars’ composition)?

Compare the star’s spectrum with known elemental spectra; identify matching lines to determine which elements are present (neutral and ionic lines).

What is the Bohr model's explanation for spectral lines?

Electrons occupy fixed energy levels; spectral lines arise from transitions between energy levels, with energy differences determining the emitted photon wavelengths.

What is the visible region of the hydrogen spectrum and which series contribute to it?

The Balmer series produces visible lines (transitions to n=2); Lyman (n→1) is in the UV and Paschen (n→3) is in the IR.