Why do you think the mass of the carbon atom shown is 12 atomic mass units (amu)?

The mass of Carbon-12 is exactly 12 amu. But, that is not the number that is reported in your periodic table. Carbon as it exists in nature is not all carbon-12. There is some small amount of carbon-13 and even traces of carbon-14 in there. The periodic table reports the average mass of the carbon as it is found in nature, not that of pure carbon-12. The average mass of carbon is slightly heaver than carbon-12, because of the slight amounts of those heaver isotopes of carbon in nature.

Mark me as brainliest please

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