Which of the following statements about atoms is true? a. Atoms are only about 10^-10m across
b. The atom is the smallest particle that uniquely defines an element, like a fingerprint
c. Atoms are comprised of a nucleus and a cloud of electrons
d. All of the above three answers are correct
e. None of the above

d. All of the above three answers are correct

Explanation:

Atoms are themselves built up from many smaller particles. According to Rutherford's nuclear theory (1906), the neutron and proton make up the nucleus of the atom.  Atoms are electrically neutral because they contain the same number of electrons and protons. The size of atoms is about meters. The fundamental particle of the atom is the electron.

- 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

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