Find the oxidation number of chromium in K2Cr2O7

The oxidation state of chromium is +6

Explanation:

Let the oxidation number be x

Since The sum of all oxidation numbers are equal to zero,

So,

(+1)2 + 2x + (-2)7 = 0

+2 +2x -14 = 0

2x-12 = 0

2x = +12

Dividing 2 to both sides

x = +6

- 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