TSR Wiki > Study Help > Subjects and Revision > Revision Notes > Chemistry > Covalent Radius
Covalent Radius
- Half the distance between two identical atoms bonded together by a single covalent bond. Nobel gases do not have a covalent radius because they do not form covalent bonds.
Trends
- Across a period, covalent radius decreases because effective nuclear charge increases (due to an increase in no. of protons and little increase in shielding) therefore shells are pulled closer towards the nucleus.
- Covalent radius increases down a group due to the constant effective nuclear charge and increase in no. of shells at increasing distances from the nucleus.
- Covalent radius is constant across the first row of transition metals because despite an increase in no. of protons across the period, electrons enter the inner 3D subshell, therefore the increase in nuclear charge is shielded so all the transition metals feel the same effective nuclear charge.
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