Question

What is the relative mass of an electron?

a) 1/1840 the mass of a neutron + proton

b) 1/1840 the mass of an alpha particle

c) 1/1840 the mass of a C-12 atom

d) 1/1840 the mass of a hydrogen atom

Answer 1

d) 1/1840 of hydrogen atom mass is the relative electron mass.

Step-by-step explanation:

The hydrogen gas is the lightest element and its atomic mass is
`\bold{1.67 * 10^(-27) \ kg}`, same as the mass of proton because it has no neutron and contains one proton and one electron in its atom. But it loses an electron to gain stable electronic configuration leaving only a proton in its atomic structure.

We know, Mass of an electron =
`9.11 * 10^(-31) \ kg`

`\text{Relative mass of electron} = \frac{\text{Mass of proton}}{\text{Mass of electron}}`

Relative mass of electron =
`(1)/(1840)` the mass of proton

Relative mass of electron =
`(1)/(1840)` the mass of hydrogen atom.

Answer 2

1/1840 the mass of a C-12 atom

Choice C is correct

Step-by-step explanation:

The relative mass of an electron is 1/1840 the mass of a C-12 atom . Atomic mass units are expressed relatively to the atomic mass unit of an unbound neutral carbon-12 atom.