(2) What is the relationship between what you know and what you need to find out? The period 2 elements are: lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine and neon. (b) Aqueous solution of combustion product turns blue limus red (a) Physical appearance at room temperature and pressure: black solid (1) What information (data) have you been given in the question? What is the question asking you to do? Name the period 2 element. This trend of increasing electronegativity across period 2 from left to right is shown in the table below: If we consider the ability of an atom of each period 2 element to attract elctrons towards itself (its electronegativity) we would expect the elements on the right which have a smaller atomic radius and greater nuclear charge to be better at this than those atoms on the left hand side of the period. This suggests that elements on the left hand side of the period 2 are more likely to form positive ions, that is lose an electron, than elements on the right hand side of period 2. In general, the energy required to remove an electron from each atom in period 2 increases as you go from left to right across the period. The trend from conductor to poor conductor to insulator across period 2 from left to right confirms the trend from metal to semi-metal (metalloid) to non-metal. Similarly, there are no mobile electrons to conduct electricity in the structure of the other non-metals. The delocalised electrons between the carbon layers of graphite allow electricity to be conducted in this way, but the electrons are "locked up" in covalents bonds in the diamond structure so diamonds do not conduct electricity, diamond is an insulator. Lithium and beryllium are metals.Īt room temperature, boron is a poor conductor of electricity, but its conductivity increases when it is heated. The delocalised electrons in the structure of a metal allows metals to conduct electricity well. So, we see a trend from high to low melting points across period 2 from left to right, a trend from solid to gas, as well as a trend from metal to semi-metal to non-metal, and a trend from metallic bonds to covalent network solid to diatomic molecules to monatomic gas: It requires a lot of energy to disrupt these strong covalent bonds holding the carbon atoms in place in the lattice so the melting point of carbon (either as graphite or diamond) is high. What about the high melting point of carbon, is carbon a metal?Ĭarbon has other properties that make it definitely a non-metal, such as the formation of covalent bonds between carbon atoms which produce large (infinite) 3-dimensional lattices that make graphite and diamond (see allotropes). The melting point of boron is very high, so is it a metal? ,īoron has other properties such as being a semiconductor, not a metallic conductor which place it in the borderline region between being a metal and a nonmetal so we shall classify it as a semi-metal (or metalloid). ![]() Strong metallic bonds hold the "atoms" in a 3-dimensional array and it requires a lot of energy to disrupt these attractive forces so the melting points are high. The elements on the left, lithium and beryllium have high melting points and are metals. ![]() Only weak intermolecular forces (London forces or dispersion forces) act between these covalent molecules, so little energy is required to disrupt the attraction and melt the solid, or indeed, boil the liquid to produce a gas. In fact, apart from neon which exists as a monatomic gas (Ne (g)) at room temperature and pressure, the others are all diatomic gases, nitrogen gas (N 2(g)), oxygen gas (O 2(g)) and fluorine gas (F 2(g)). The elements on the right, nitrogen, oxygen, fluorine and neon all have low melting points and are all non-metals.
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