Earth materials: Atoms, bonding and measurements of matter

week 1: 21.09.26

what is a mineral?

naturally occurring inorganic solid with an ordered atomic arrangement and definite chemical composition.

what is a rock?

naturally occurring solid mass which is an aggregate of one or more minerals

how many known minerals are there?

around 3000

what does crystalline mean?

the atoms possess an ordered atomic arrangement

why is glass not crystalline?

atoms are not ordered and it has the structure of a liquid

how does glass form?

rapid cooling

what determines a crystals external morphology?

reflects the hexagonal symmetry of the crystal structure

how do crystals grow?

grow by adding atoms to their edges

what is a euhedral crystal?

a crystal that has the opportunity to grow into open space allowing it to form a well developed crystal shape

what is a subhedral crystal?

when the growth of a crystal is constrained so do not show recognisable faces therefore are imperfect but show some evidence of ideal form

what are atoms composed of?

protons, neutrons, electrons

what is the relative mass of a proton?

1

what is the relative charge of a proton?

+1

what is the relative mass of a neutron?

1

what is the relative charge of a neutron?

0

what is the relative mass of an electron?

1/1840

what is the relative charge of an electron?

-1

what is the atomic number?

number of protons in the nucleus + number of electrons

what is the mass number?

number of protons and neutrons

how is mass and atomic number displayed on the periodic table?

what are isotopes?

elements that have the same number of protons but different number of neutrons

what are isotopes useful for in geology?

useful in giving absolute dates to minerals and rocks as certain isotopes undergo radioactive decay to another isotope at a constant rate and some a fractionated by natural mass dependent processes

how can analysing carbon isotopes help determine its origin?

during photosynthesis, plants prefer ¹²C rather than ¹³C therefore by analysing the ratio of isotopes it may be possible to tell whether the carbon originated organically or by precipitation from seawater

why are noble gases more stable?

have 8 electrons in the outer shell

how do atoms gain a stable electron cofiguration?

by bonding

what are cations?

positively charged ions

what are anions?

negatively charged ions

what is ionic bonding?

elements gain or lose electons to form ions with a full outer shell

what is covalent bonding?

atoms attain the noble gas structure and bonds by sharing electrons

what is Van Der Waals bonding?

weak residual forces that exist between all atoms

what is metallic bonding?

• metals consist of ions bound together by a sea of electrons. these electrons are free to move through the structure

what is Avogadro’s number?

6.022 × 10²³

what is the formula for mass, moles and relative atomic mass?