S1.2 The nuclear atomIB Chemistry SL: Flashcards

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What particles make up the nucleus?

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What particles make up the nucleus?: Protons and neutrons (nucleons).
What are the relative charges of a proton, neutron and electron?: +1, 0 and −1.
What does A represent in a nuclear symbol?: The mass number: the number of protons plus neutrons.
What does Z represent in a nuclear symbol?: The atomic number: the number of protons.
How many neutrons are in ³⁹K?: 39 − 19 = 20.
How many electrons are in O²⁻ (Z = 8)?: 8 + 2 = 10.
Define isotopes.: Atoms of the same element with the same number of protons but different numbers of neutrons.
Why do isotopes have the same chemical properties?: They have the same number and arrangement of electrons, and chemical reactions involve electrons.
Name two physical properties that differ between isotopes.: Density and boiling point (also rate of diffusion, melting point).
Define relative atomic mass.: The weighted mean mass of an element's atoms relative to one-twelfth of the mass of a carbon-12 atom.
Why is Ar usually not a whole number?: It is a weighted average of the masses of the element's isotopes.
What did the gold-foil experiment show?: Atoms are mostly empty space with a small, dense, positively charged nucleus.
Chlorine has Ar 35.5 with isotopes 35 and 37. What are the abundances?: 35x + 37(1 − x) = 35.5, so 75 % chlorine-35 and 25 % chlorine-37.