Chapter 2 Flashcards
What is the electrical charge on a proton? A neutron? An electron? What are their relative masses?
Charges: proton: +1, neutron: 0, electron: −1, Masses: proton: 1, neutron: 1, electron: almost 0.
Explain how the need for an atom’s outer shell to be filled with electrons contributes to bonding.
The element’s atomic number will determine the extent to which its outer layers are populated with electrons. If the outer shell is not quite full, the atom may gain electrons to fill them and become an anion (negative charge). If the outer shell has only a few electrons, it may lose them and become a cation (positive charge). Cations and anions attract each other to form molecules with ionic bonding.
Why are helium and neon non-reactive?
Helium and neon (and the other noble gases) have complete outer shells and therefore no tendency to form ionic bonds.
What is the difference in the role of electrons in an ionic bond compared to a covalent bond?
Electrons are transferred from one atom to another to form an ionic bond. Electrons are shared between atoms to form a covalent bond.
What is the electrical charge on an anion? A cation?
An anion has a negative charge and a cation has a positive charge.
What chemical feature is used in the classification of minerals into groups?
Minerals are classified into groups based on their anion or anion group.
Name the mineral group for the following minerals: calcite gypsum hematite quartz biotite galena graphite fluorite pyrite orthoclase magnetite olivine
calcite – CaCO3, carbonate gypsum – CaSO4, sulphate hematite – Fe2O3, oxide quartz – SiO2, silicate biotite – silicate galena – PbS, sulphide graphite – C, native fluorite – CaF2, halide pyrite – FeS2, sulphide orthoclase – KAlSi3O8, silicate magnetite – Fe3O4, oxide olivine – MgSiO4, silicate
What is the net charge on an unbonded silica tetrahedron?
An unbonded silica tetrahedron has one Si ion (+4 charge) and 4 oxygens (−2 charge each) so the overall charge is 4 − 8 = −4 for SiO4−4
What allows magnesium to substitute freely for iron in olivine?
Magnesium can substitute freely for iron in olivine and several other minerals because they have similar charges (+2) and similar ionic radii.
How are the silica tetrahedra structured differently in pyroxene and amphibole?
Pyroxene is made up of single chains of tetrahedra while amphibole is made up of double chains.
Why is biotite called a ferromagnesian mineral, while muscovite is not?
Biotite includes iron and/or magnesium in its formula, while muscovite does not.
What are the names and compositions of the two end-members of the plagioclase series?
The two end-members of the plagioclase series are Albite (NaAlSi3O8) and Anorthite (CaAl2Si2O8)
Why does quartz have no additional cations (other than Si+4)?
In quartz each silica tetrahedron is bonded to four other tetrahedra, and since oxygens are shared at each bond the overall ratio is silicon (+4) to two oxygens (2 × −2 = −4), which is balanced.`
Why is colour not necessarily a useful guide to mineral identification?
Some minerals have distinctive colours, but many have a wide range of colours due to differing impurities.
You have an unknown mineral that can scratch glass but cannot scratch a porcelain streak plate. What is its approximate hardness?
Glass has a Mohs hardness of about 5.5 while porcelain is close to 6.5. The mineral is between these two, so it must be close to 6.
