![]() ![]() (ii) A dative bond is a covalent bond in which both the shared electrons are provided by one atom only.įactors that promote the formation of complex ions (i) A complex ion is a cation bonded to small molecules called ligands by dative bonds. The coloured flames can be used to identify these metals or their salts (iii) The melting point of beryllium is higher than expectedĬalcium, strontium and barium give characteristic flame colourations (ii) group 2 elements have higher melting points than group 1 elements? (i) the melting point of magnesium is lower than expected. This is the reason why the melting and boiling points generally decrease down the group as atomic size increase. Nuclear charge: small atoms with a high nuclear charge for delocalized electrons form stronger metallic bonds than bigger atoms.The bigger the number of electrons contributed to the formation of a metallic bond, the stronger the metallic bonds. The strength of metallic bonds increases with the number of electrons contributed by each metal atom in the electron cloud in the formation of metallic bonds.Factors affecting the strength of metallic bonds include (d) The melting and boiling points of beryllium are higher than expected, because beryllium has a small atomic size and shows non-metallic behaviour, it forms strong Be-Be covalent bonds that lead to high melting and boiling points. Whereas Group 1 elements have 1 electron in the outermost shell and contribute one electron to form weak metallic bonds (c) The melting and boiling points of alkaline earth metals are higher than those of the alkali metals because they contribute 2 electrons to form a stronger metallic bond. (b) The melting point of magnesium is lower than expected probably because magnesium atoms are loosely packed in the metal crystal and experience low interatomic attractions. The strength of metallic bonds decreases down the group due to a decrease in nuclear attraction to the delocalized electrons as the electronegativity decrease. The melting points of group 2 generally decrease down the group due to the decrease in the strength of metallic bonds. The melting points generally decrease down the group as shown below Give one reason to explain why the elements of group II of the periodic table are strong reducing agents.Ī. Explain how the following factors vary within the group. The elements Be, Mg, Ca, Sr, Ba are in group II of the Periodic table. Both nuclear charge and screening effect increase but an increase in screening effect outweighs the increase in nuclear charge. ![]() Down the group, the number of electron shells and protons increases. Increase down the group due to a decrease in effective nuclear charge. The metallic property increases down the group.ĭecreases down the group because an increase in screening effect outweighs increases in nuclear attraction as the number of electron shells increase.Įlectronegativity is the relative tendency of an atom to attract bonding electrons. However, Group 2 elements are highly metallic that they form mainly ionic compound. Group 2 elements have higher ionization energy than group 1 elements, leading to less ionic compounds since less energy is required to form M + than M 2+. The ionization energy decreases down the group due to the decrease in the effective nuclear charge.ĭown the group both the nuclear charge and screening effect increase but increase in the screening outweighs the increase in nuclear charge.ī. increase in the screening effect of the inner electronsĪ.Increase in the number of electron shells.Explain.Ītomic radii of group 2 elements increase down the group due Has very high ionization energy that it hardly form Be 2+ ions leading to covalent compounds.īeryllium chloride is more soluble in ethanol than in water whereas magnesium chloride is more soluble in water than in ethanol.The chemistry of Beryllium differs considerably from the other members of the group because it has Some physical properties of group 2A elements are given in a table below: Uniqueness of Beryllium Radium is radioactive.Īll the members of this group are highly reactive and are essentially found as compounds in nature. The members of group 2A or the alkaline earth metals are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). ![]()
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