atomic structure

Question 1

What are isotopes?

Answer 1

Isotopes are atoms of the same element but with different number of neutrons.
To find relative atomic mass from isotopes:
(percentage/100 x mass number) + (percentage/100 x mass number)

Question 2

What is another phrase that means the same thing as “principal quantum shell”?

Answer 2

Electron shell (each principal quantum number corresponds to an electron shell)

Question 3

1s^2. What does 1, s and ^2 represent?

Answer 3

1: energy level (principal quantum number)
s: type of orbital (s, p, d, f)
^2: number of electrons in orbital (for s, max 2 while for p, max 6)

Question 4

Electrons are removed from orbitals with the ___ principal quantum number first.

Answer 4

Electrons are removed from orbitals with the highest principal quantum number first.

Question 5

An atom is in the ___ ___ when the electrons are in the orbitals of ___ available energy level.
An atom is in the ___ ___ when one or more electrons absorb energy and are promoted to a ___ energy level.

Answer 5

An atom is in the ground state when the electrons are in the orbitals of lowest available energy level.
An atom is in the excited state when one or more electrons absorb energy and are promoted to a higher energy level.

Question 6

What is the ionisation energy of an element?

Answer 6

It is the energy required to remove an electron from its gaseous atom/ion in its ground state. It measures the ease of an atom/ion losing an electron.

Question 7

How to represent ionisation energy in the form of a chemical equation?

Answer 7

X (g) –> X^+ (g) + e^- (electrons have no state symbols!!)

*in IE, every particle must be in gaseous state!!

Question 8

Successive ionisation energies increase because…

Answer 8

After the removal of the first electron, a positively-charged ion is formed. A greater amount of energy is needed to remove electrons from a cation as compared to a neutral ion.

Question 9

Sharp increases in ionisation energy is due to…

Answer 9

It is due to the removal of a x electron for the y IE compared to the removal of a z electron (an electron farther to the nucleus) for the (y-1) IE. The x electron is more strongly attracted to the nucleus than the z electron. Hence much more energy is required to remove the x electron as it is from an inner electron shell.