The ionization state of amino acids is altered by a change in ph. at low ph, near the p k a pka for the carboxylic acid, the − cooh −cooh proton is lost from the fully protonated form. as the ph approaches physiological levels, the zwitterionic form predominates. at high ph, near the p k a pka for the amino group, one of the − nh + 3 −nh3+ protons is lost to form the fully deprotonated species.

The pH at which amino acid would not have net charge is 6

From the graph , it is obvious that zwitterion form that carries no net charge of amino acid exist at pH 4 to 8 .

The Pink line shows the ionisation of carboxylic acid and green line shows ionisation of ammonium ion .

pH at which none of the green and pink line exist is the pH where complete zwitterion form exist ( having no net charge ) .

So, pH 6 is the correct answer .

Explanation:

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms