What are proper units for density for a solid, liquid or gas

Density of a substance is defined as the mass occupied by the substance per unit volume. Mathematically it can be expressed as:

Density = Mass/Volume

i.e. ρ = m/V

In SI units, the mass is expressed in kilograms (kg) and the volume in cubic meters (m3). Thus,

Density = kg/m3

SI units for density = kg/m3

- 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