Homework 1 - Myweb @ CW Post

Earth Materials - GLY 26
Homework Set 1
Fall 2013
due Wed, Feb 6
Earth origin & composition
1)! Describe, compare, and contrast the compositions of the core, mantle, oceanic
crust, and continental crust. Be concise but complete.
atoms, elements, periodic table, bonds
2)! Write out the electron configuration (s,p,d,f “stuff”) for an element with 14 electrons in
the neutral atom and an element with 30 electrons in the neutral atom. What are
these elements
3)! When atoms bond they do so in such a way as to modify their electron configuration
to achieve a lower energy state by either completely filling, half-filling, or emptying
the available orbitals of the valence shell. Many elements may take on more than
one valence state (+ or 1 depending on numbers of electrons accepted or donated).
Tell why the following elements take on their particular valence states (tell what
orbitals gain or lose electrons and how many).
a) Na: +1! b) Ca: +2! c) Cl: -1! d) O: -2
e) Si: +4! f) Al: +3! g) Fe: +2! h) Fe: +3
4)! Based on their normal valence states, list the chemical formula for each of the
following pairs.
a) Na & Br! b) Mg & Cl! c) Ca & S! d) Mg & O! e) Al & O!
f) Fe III (Fe in the +3 valence state) & O
g) Ca & the carbonate ion (first determine what the net charge of CO3 is)
5)! Determine the percent ionic character of the following bonds based on the
electronegativity differences. Use Table 2.3 for the electronegativites. It is missing
the following electronegativities (Cl: 3.0, Si: 1.8, Al: 1.5). Find the Percent Ionic
Character using Table 7.2 from Faure (1998) included at the end of this document.
Interpolate values from the table (donʼt just pick the closest ionic character).
a) Na-Cl! e) Si-O! i) Na-O
b) O-O! f) Al-O! j) K-O
c) H-O! g) Fe-O! k) Mg-O
d) C-O! h) Ca-O

---! Next, list bonds e-k, in order from most covalent to most ionic. Notice that these
are the major elements bonding with oxygen as in silicate minerals.
coordination polyhedra & ionic substitution
6)! Using Figures 2.7-2.8 and Table 2.5 in the textbook, determine the coordination
number and type for the following ions.
! Note: the values listed in Figs 2.7 & 2.8 are for general use but not necessarily the
specific radius in a given compound. The radius listed for Si +4 in b) below is specific
for its bonding with oxygen and differs from the general radius given in Fig 2.7.
! a) Na + relative to Cl - in halite (Cl- ionic radius: 1.72 Å)
! b) Si +4 relative to O -2 in silicates (Si +4 ionic radius here is ~0.34 Å; Faure, 1998)
! c) Al +3 relative to O -2 in silicates
! d) Na + relative to O -2 in silicates
! e) Fe +2 relative to O -2 in silicates
7)! Atomic and ionic radii vary with valence state but also with the type and number of
surrounding ions (for example, see Table 2.6). Determine the coordination number
and type for carbon in carbon dioxide and in carbonate ions:
! a) C +4 relative to O -2 in CO2 (radius of C +4 in CO2: 0.16 Å)
! b) C +4 relative to O -2 in CO3 -2 (radius of C +4 in CO3 -2 : 0.29 Å)
!
8)! Determine whether the following substitutions will occur. Show why or why not, and
if coupled substitution is required. Use Figure 2.7 and Table 2.6 for cation radii (note
correct coordination in Table 2.6).
a) will Mg +2 substitute for Fe +2 bonded to O -2 in silicates
! b) will Ca +2 substitute for Na + bonded to O -2 in silicates
! c) will K + substitute for Na + bonded to O -2 in silicates

9)! The ternary diagram below is Figure 3.3 from p. 48 of the textbook. Plot the
compositions of the following two carbonate samples on the diagram (use points A &
B from the text as a guide for how to plot).
!
! c) (Fe0.2, Mg0.8)CO3
! d) (Fe0.8, Mg0.15, Mn0.05)CO3
silicates
10)!Is quartz, SiO2, is electrically neutral or charged.
11)! Determine whether an isolated silica tetrahedron, SiO4, is electrically neutral or
charged, and if charged, what its charge is. If charged, how is the charge
neutralized
12)!Describe the changing ratio of silicon and oxygen (the formula) in isolated silica
tetrahedra, single chains of silica, double chains, silica sheets, and the framework
structure of quartz.

=========================== for use with #5 ===========================
from Faure (1998)