Please answer it correctly thank you Question 2: Elements and minerals (20 marks
ID: 117781 • Letter: P
Question
Please answer it correctly thank you
Question 2: Elements and minerals (20 marks total] Based on when and how elements were formed, it is possible to subdivide all elements in the periodic table excludiné man-made elements) into three major groups. ) List these three groups [3 marks) Indicate for each group: When they were formed in the stellar/universe evolution; [3 marks) How they were formed (note that a description is sufficient, reactions are not required). [4 marks) Silicate minerals form the largest group of minerals on Earth. by Describe the fundamental (chemical) building block of ALL silicate minerals. [4 marks) Different groups of silicate minerals (six in total) can be identified based on the number of non-bonding oxygens per building block (NBO/T). Page 1 of 2Explanation / Answer
a) The 3 groups are:
Bigbang elements, supernova elements and cosmic rays elemets.
i) H and He are the bigbang elements forn during the big bang around 14.5Ga. Li, Be, and B are Cosmic ray elemets formed just afetr the bing bang in a fraction of second. And rest of them are supernova and large stars elements formed during supernova explosion .
ii) During ‘Big Bang’, only the lightest elements were formed – hydrogen and helium (2 hydrogen fuse togetehr to form He) along with trace amounts of lithium and beryllium ( He+ H=Li, 2He=Be), whic is considerd as a cosmic ray elements.The other 86 elements found in nature were created in nuclear reactions in these stars and in huge stellar explosions known as supernovae.
H2 + H2 = 4He
3 * 4He 12C
12C + 4He 16O
16O + 4He 20Ne
20Ne + 4He 24Mg and so on.
b) The basic building block of all silicate minerals is the [SiO4]4 tetrahedron. There are four covalent SiO bonds. Each oxygen atom forms one vertex of the tetrahedron. The silicon to oxygen atom ratio is 1:4. Because the SiO4 is not electronically neutral (Si4+ + 4O2 - = -8) it tends to combine with other elements to make a neutral species. The variety of silicate minerals is produced by the (SiO4)4- tetrahedra linking to self-similar units sharing one, two, three, or all four corner oxygens of the tetrahedron.
The 6 silicate mineral gropus are:
Nesosilicates – (Orthosilicates) : Isolated (SiO4)4- tetrahedra and bounded to one another via ionic bonds with interstitial cations. eg. Olivine
Sorosilicates – (Disilicates) : SiO4 tetrahedra in combination with Si2O7 units. These commonly form edge-sharing linked octahedral chains.These chains in-turn form sheets by binding with isolated SiO4 tetrahedra. eg. Epidote.
Cyclosilicates – (Ring silicates): 3, 4, 6, 8, 9, or 12 membered rings of Si4+ tetrahedra (though 6-membered are the most common) • These are similar to the Framework silicates in that the ratio of cations in the tetrahedral site (Si) to oxygen is 1:2. eg. Beryl.
Inosilicates - (chain silicates) : Inosilicates, or chain silicates, have interlocking chains of silicate tetrahedrons.The most important two mineral groups are the pyroxenes and the amphiboles. eg. Tremolite.
Phyllosilicates – (Silicate Sheets):Sheet silicate minerals, formed by parallel sheets of silicate tetrahedrons Si2O52-.Many members have a platy or flaky habit with one very prominent cleavage. Minerals are generally soft, low specific gravity, may even be flexible. Most are hydroxyl bearing. eg. Mica.
Tectosilicates – (Framework Silicates): Infinite 3-dimensional network of (SiO4)4- or (Si3Al)O81- - (Si2Al2)O82- building blocks. All oxygen atoms are shared between two SiO4 4- tetrahedron. eg. Feldspar group mineral, quartz.