Mass Number & Isotopes

Question 1

Electrons orbit the nucleus of the atom, contributing very little to its overall mass, but creating a ‘….’ of negative charge

Answer 1

cloud

Question 2

An atom is ……. and has no overall charge

Answer 2

neutral

a ion is a charged particle

Question 3

Isotopes are atoms of the same element that contain and what is the symbol

Answer 3

the same number of protons and electrons but a different number of neutrons

The symbol for an isotope is the chemical symbol (or word) followed by a dash and then the mass number
E.g. carbon-12 and carbon-14 are isotopes of carbon containing 6 and 8 neutrons respectively

Question 4

Isotopes have the same ……… properties but different …….. properties

Answer 4

chemical

physical

Question 5

Why do isotopes of an element have the same chemical properties

Answer 5

This is because they have the same number of electrons in their outer shells
Electrons take part in chemical reactions and therefore determine the chemistry of an atom

Question 6

Why do isotopes of an element have different physical properties

Answer 6

Since these are neutral subatomic particles, they only add mass to the atom

As a result of this, isotopes have different physical properties such as small differences in their mass and density

Question 7

Because of this, the mass of an element is given as relative atomic mass (Ar) by using the average mass of the isotopes

The relative atomic mass of an element can be calculated by using the relative abundance values

what is the formula

Answer 7

(relative abundance isotope 1 x mass) + (relative abundance isotope 2 x mass)

DIVIDE BY

100

Question 8

relative atomic mass of a element is defined as

Answer 8

the average mass of an atom of an element relative

divide by

one twelfth of the mass of an atom of carbon-12.