This page covers the shapes and angles of beryllium chloride molecule, beryllium fluoride, beryllium bromide, beryllium iodide, magnesium fluoride, magnesium chloride, magnesium bromide, magnesium iodide

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Lewis dot and cross electronic diagram used to predict the shape of group 2 halide molecules in the gaseous state.

Q-X-Q  symmetrical linear shape, bond angle 180^o

Gaseous group 2 halides XQ₂ (X = Be or Mg and Q = F, Br, Cl or I)

From the periodic table and Z, the outer electron configurations are:

for the group 2  alkaline earth metals they are Be 2s² and Mg 3s²

for the group 7/17 halogens they are ns²p⁵ where n = 2 (F), 3 (Cl), 4 (Br) and 5 (I)

Be and Mg are group 2 elements with two outer valence electrons and so can form two single covalent bonds - 2 bond pairs with halogen atoms, which have one electron short of the stable octet of valence electrons and so can form a single covalent e.g. Be-Cl.

VSEPR theory argument predicts a linear shaped Q-X-Q molecule because there only two groups of bonding electrons around the central atom mutually repelling other to the maximum angle of 180^o (this assumes we are dealing an isolated molecule in the gaseous state).

This applies to gaseous beryllium halides BeF₂, BeCl₂, BeBr₂ and BeI₂

The same VSEPR arguments apply to gaseous magnesium halides MgF₂, MgCl₂, MgBr₂ and MgI₂

When condensed all beryllium halides form solid complex polymeric structures

When condensed all magnesium halides form solid essentially ionic compounds.

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Position of the elements ? and ? in the Periodic Table

Pd	s–block metals			p–block metals and non-metals  (p-block old/new IUPAC group numbering)
	Gp1	Gp2		Gp3/13	Gp4/14	Gp5/15	Gp6/16	Gp7/17	Gp0/18
1	[1H] (hydrogen does not really fit into any group)								2He
2	3Li	4Be		5B	6C	7N	8O	9F	10Ne
3	11Na	12Mg	Selected elements of the Periodic Table ZSymbol, Z = atomic/proton number No d block, f block or period 7 elements are shown	13Al	14Si	15P	16S	17Cl	18Ar
4	19K	20Ca		31Ga	32Ge	33As	34Se	35Br	36Kr
5	37Rb	38Sr		49In	50Sn	51Sb	52Te	53I	54Xe
6	55Cs	56Ba		81Tl	82Pb	83Bi	84Po	85At	86Rn

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 LINKS

 Home page of Doc Brown's Advanced A-Level pre-university/college chemistry

 My original page on VSEPR theory of shapes of selected molecules and ions

 My new extended INDEX of shapes of selected molecules and ions

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