T-cell costimulatory

TLS Online TPP Program

#Id: 7751

#Section 2: General Biology

Ranks the following in increasing atomic radius

S, Mg, Al

S: 16-10 +6

Mg: 12-10 = +2

Al: 13-10 +3

So: S < AlMg

TLS Online TPP Program

#Id: 7750

#Section 2: General Biology

The greater the effective nuclear charge the more tightly an electron is held in by the nucleus because there is less electron shield between the valence electrons and the nucleus, and so, the smaller the radius.

TLS Online TPP Program

#Id: 7749

#Section 2: General Biology

    

TLS Online TPP Program

#Id: 7748

#Section 2: General Biology

Zeff=Z –S

Chlorine would have a Z value of 17 (the atomic number of Chlorine). Continuing to use Chlorine as an example, the 10 inner electrons (S) would screen out the positive charge of ten protons. Therefore there would be and effective nuclear charge of 17-10 or +7.

TLS Online TPP Program

#Id: 7747

#Section 2: General Biology

Size of atom or atomic radii can be estimated by effective nuclear charge

TLS Online TPP Program

#Id: 7746

#Section 2: General Biology

The noble gases are left out of the trends in atomic radii because there is great debate over the experimental values of their atomic radii.

The SI units for measuring atomic radii are the nanometer (nm) and the picometer (pm). 1 nm = 1 X 109 m; 1 pm = 1 X 10-12 m.