3c. Electron configuration, elements in the periodic table forming covalent bonds

Doc Brown's Chemistry: Chemical Bonding and structure GCSE level, IGCSE, O, IB, AS, A level US grade 9-12 level Revision Notes


Which elements from the periodic table combine to form covalently bonded molecules?

Its a good idea to have some idea of where the elements are in the periodic table, and their electronic structure, before looking at the theoretical electronic model for covalent bonding in molecules (elements or compounds).

The black zig–zag line 'roughly' divides the metals on the left from the non–metals on the right of the elements of the Periodic Table - combining elements on the right usually results in a covalent bond.

(c) doc b

The electronic structures of the first 20 elements of the Periodic Table

You need to know these to understand the details of covalent chemical bonding and working out dot and cross electronic diagrams of molecules (GCSE level)

Pd metals Part of the modern Periodic Table

Pd = period, Gp = group

metals => non–metals
Gp1 Gp2 Gp3 Gp4 Gp5 Gp6 Gp7 Gp0
1

1H  Note that H does not readily fit into any group

2He
2 3Li 4Be atomic number Chemical Symbol eg 4Be 5B 6C 7N 8O 9F 10Ne
3 11Na 12Mg 13Al 14Si 15P 16S 17Cl 18Ar
4 19K 20Ca 21Sc 22Ti 23V 24Cr 25Mn 26Fe 27Co 28Ni 29Cu 30Zn 31Ga 32Ge 33As 34Se 35Br 36Kr
5 37Rb 38Sr 39Y 40Zr 41Nb 42Mo 43Tc 44Ru 45Rh 46Pd 47Ag 48Cd 49In 50Sn 51Sb 52Te 53I 54Xe
6 55Cs 56Ba Transition Metals 81Tl 82Pb 83Bi 84Po 85At 86Rn
Gp 1 Alkali Metals  Gp 2 Alkaline Earth Metals  Gp 7 Halogens  Gp 0 Noble Gases

Chemical bonding comments about the selected elements highlighted in white

Two of the highlighted non–metals on the right of the periodic table (and hydrogen) may combine with each other OR with themselves. In doing so, covalent bonds are formed, e.g. the formation of a covalent compounds like hydrogen chloride gas HCl, sulfur dioxide gas SO2, liquid water H2O, and element molecules like hydrogen H2 or oxygen O2.

A bigger picture, but not exclusively is shown below

Pd metals Part of the modern Periodic Table

Pd = period, Gp = group

metals => non–metals
Gp1 Gp2 Gp3 Gp4 Gp5 Gp6 Gp7 Gp0
1 1H  Note that hydrogen does not readily fit into any group but is a non-metal 2He
2 3Li 4Be atomic number Chemical Symbol eg 4Be 5B 6C 7N 8O 9F 10Ne
3 11Na 12Mg 13Al 14Si 15P 16S 17Cl 18Ar
4 19K 20Ca 21Sc 22Ti 23V 24Cr 25Mn 26Fe 27Co 28Ni 29Cu 30Zn 31Ga 32Ge 33As 34Se 35Br 36Kr
5 37Rb 38Sr 39Y 40Zr 41Nb 42Mo 43Tc 44Ru 45Rh 46Pd 47Ag 48Cd 49In 50Sn 51Sb 52Te 53I 54Xe
6 55Cs 56Ba Transition Metals 81Tl 82Pb 83Bi 84Po 85At 86Rn
The non-metals in the Periodic Table highlighted in white, tend to form covalent bonds with each other (for GCSE level).

This might be as an element or a compound, usually forming small molecules, but sometimes a giant structure

 

Most covalent molecules you will come across are formed by combinations of atoms of non–metallic elements on the right–hand side of the Periodic Table eg

from Group 4 carbon and silicon, from Group 5 nitrogen and phosphorus and from the Group 7 Halogens – fluorine, chlorine, bromine and iodine.

Hydrogen also forms predominantly covalent compounds and so does the Noble Gas xenon in Group 0.

Don't forget, even non–metal elements can form molecules eg hydrogen H2 and phosphorus P4.

Brief summary of the Periodic Table including electronic structure and formula patterns

You should be able to from Parts 3 and 4:

know when atoms share pairs of electrons, they form strong covalent bonds,

covalently bonded substances may consist of small molecules. and recognise common substances that
consist of small molecules from their chemical formula,

know that some covalently bonded substances have very large molecules, such as polymers,

know that some covalently bonded substances have giant covalent structures such as diamond and silicon dioxide,

appreciate that covalent bonds in molecules and giant structures can be represented in various forms

draw dot and cross diagrams for the molecules like hydrogen, chlorine, oxygen, nitrogen, hydrogen chloride, water, ammonia and methane,

represent the covalent bonds in small molecules, in the repeating units of polymers and in part of giant covalent structures, using a line to represent a single bond,

describe the limitations of using dot and cross, ball and stick, two and three-dimensional diagrams to represent molecules or giant structures,

deduce the molecular formula of a substance from a given model or diagram in these forms showing the atoms and bonds in the molecule.

Be able to define empirical formula and molecular formula

Be able to calculate empirical and molecular formula from given data

 


What next?

Recommend next: The covalent bonding in the hydrogen molecule

 

Sub-index for Part 3. Covalent Bonding: small molecules & properties

 

Index for ALL chemical bonding and structure notes

 

Perhaps of interest?

Overview of the Periodic Table

 

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