Two individual atoms of the same element are slightly different. One has one more proton than it has electrons. The other has one more electron than it has protons. These atoms are both ions
isotopes
freons
xenons
phlogistons

ions

Explanation:

Individual atoms of the same element but having slightly different number of protons and electrons are called ions.

Ion is a charged particle.

When the number of protons > electrons the body is positively charged.

When the number of electrons > protons the body is negatively charged.

Charged particles are called ions.

your picture is not part of the scientific method.

- 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