Question

When conducting metal/metal ion displacement reactions in a high school laboratory, why does the precipitate metal commonly look black in colour?

Answer 1

Carbon is one of the most common elements on earth, and greatly influences everyday life. Common molecules containing carbon include carbon dioxide (CO2) and methane (CH4). Many scientists in a variety of fields study of carbon: biologists investigating the origins of life; oceanographers measuring the acidification of the oceans; and engineers developing diamond film tools. This article details the periodic properties of the carbon family and briefly discusses of the individual properties of carbon, silicon, germanium, tin, lead, and flerovium.
Introduction
The carbon family, Group 14 in the p-block, contains carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl). Each of these elements has only two electrons in its outermost p orbital: each has the electron configuration ns2np2. The Group 14 elements tend to adopt oxidation states of +4 and, for the heavier elements, +2 due to the inert pair effect.

Figure 1: Row 14 in the Periodic Table
Members of this group conform well to general periodic trends. The atomic radii increase down the group, and ionization energies decrease. Metallic properties increase down the group. Carbon is a non-metal, silicon and germanium are metalloids, and tin and lead are poor metals (they conduct heat and electricity less effectively than other metals such as copper).
Despite their adherence to periodic trends, the properties of the carbon family vary greatly. For example, carbon is a non-metal and behaves as such, whereas tin and lead behave entirely as metals. In their elemental solid states, the Group 14 metalloids silicon and germanium act as electrical semiconductors, although silicon is largely non-metallic; their electrical conductivity can be affected in various degrees by doping, or adding of Group 13 or Group 15 elements in varying concentrations to the Group 14 solid matrix. These semiconductor properties have wide application for circuitry components in the electronics industry, such as diodes, transistors, and integrated circuit (IC) chips.
Element
Carbon
Symbol
C
Atomic #
6
Atomic Mass
12.011
Classification
Non-metal
Electron Configuration
[He]2s22p2
Element
Silicon
Symbol
Si
Atomic #
14
Atomic Mass
28.0855
Classification
Metalloid
Electron Configuration
[Ne]3s23p2
Element
Germanium
Symbol
Ge
Atomic #
32
Atomic Mass
72.61
Classification
Metalloid
Electron Configuration
[Ar]3d104s24p2
Element
Tin
Symbol
Sn
Atomic #
50
Atomic Mass
118.710
Classification
Metal
Electron Configuration
[Kr]4d105s25p2
Element
Lead
Symbol
Pb
Atomic #
82
Atomic Mass
207.2
Classification
Metal
Electron Configuration
[Xe]4f145d106s26p2
Element
Flerovium
Symbol
Fl
Atomic #
114
Atomic Mass
287
Classification
Metal
Electron Configuration
[Rn]5f146d107s27p2
Carbon
Carbon is the fourth most abundant element on earth. It is of particular interest in organic chemistry, as it is the distinguishing feature of an organic compound. It is also considered the "backbone" of biology, as all life forms on earth are carbon-based. This is due to two important qualities of carbon: its small size and its unique electron configuration. Because carbon atoms are small, their p-orbital electrons overlap considerably and enable π bonds to form. Compare the molecular structures of CO2 and SiO2 below:

\(CO_2\) has double bonds between carbon and oxygen atoms, whereas \(SiO_2\) has single bonds. The \(CO_2\) molecule exists freely in the gas phase. The \(SiO_2\) molecule, by contrast, always exists within a network of covalent bonds.
Carbon's electron configuration of allows it to form very stable bonds with oxygen and hydrogen. These bonds store an enormous amount of energy. The formation (fixation) and breakage (combustion) of these bonds in the carbon cycle facilitate earthly life:
Carbon fixation: In photosynthesis, plants use energy from the sun and chlorophyll molecules to turn gaseous carbon dioxide from the atmosphere into simple carbohydrates like glucose:
6CO2 + 6H2O + energy → C6H12O6 + 6O2
Carbon