2. Atomic Structure

Question 1

Isotopes

Answer 1

Atoms of the same element with the same atomic number but different mass number

• Same chemical properties (same amount of e^-)
• Slightly different physical properties (different amount of neutrons)

Question 2

Radio Isotopes

Answer 2

Isotopes that have unstable nuclei and therefore emit radiation when they break up

Uses

• carbon dating
• radio therapy
• medical tracers
• nuclear power

Question 3

Wavelength (frequency and energy)

Answer 3

The shorter the wavelength the higher the frequency of the wave and the more energy it contains

Question 4

Emission Spectra

Answer 4

When electrons are excited to a higher energy level, and then return to a lower energy level, they release a photon of a specific energy, as shown by a specific frequency of light

*electrons moving back to the lowest energy states and over longer distances release more energy

as the electron moves to higher energy states, the spectral lines converge

Question 5

Lyman series

Answer 5

U.V. radiation

from a higher sublevel to n=1

Question 6

Balmer Series

Answer 6

Visible light radiation

From a higher sublevel to n=2

Question 7

Paschen

Answer 7

Infrared radiation

From a higher sublevel to n=3

Question 8

Electronic Configuration

Answer 8

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶….

(4s electrons are lost first in transition metals)

Question 9

Aufbau Principle

Answer 9

The order in which the energy levels are filled

2 exceptions:

chromium and copper fill up 3d first / electrons from 4s are lost first

Question 10

Hund’s Rule

Answer 10

Electrons prefer to occupy orbitals on their own, and only pair up when no empty orbitals of the same energy are available

Question 11

Pauli Exclusion Principle

Answer 11

Paired electrons have the opposite spin as this reduces the mutual repulsion between the paired electrons

Question 12

First Ionization Energy

Answer 12

The energy required to remove one mole of electrons from one mole of atoms in the gaseous state to form one mole of univalent cations in the gaseous state

X_(g) –> X⁺ + e^- +ve dH

Question 13

Factors affecting ionization energy

Answer 13

• Size of the nuclear charge - the larger the nuclear charge, the larger the force of attraction so the greater ionization energy required
• Distance of the electron from the nucleus - the farther away the electron is from the nucleus, the smaller the force of attraction

Question 14

Successive Ionization energy

Answer 14

X⁺_(g) –> X²⁺_(g) + e^-

• Increases because electrons are being removed from increasingly positive ions –> larger nuclear attraction
• Large jumps seen when electron is removed from a new sublevel closer to the nucleus

Question 15

Ionization Energy Trends on a Periodic Table - Across a period

Answer 15

• Size of the 1st I.E. increases - e^- comes from the same sublevel but the nuclear charge increases
• The first I.E. of Al is less than that of Mg - the e^- removed from Al is at a higher sublevel
• The first I.E. of S is less than that of P - electron removed from 3p is a paired e^-
  
  • ^​when paired, extra mutual repulsion results in less required energy to remove

Question 16

Ionization Energy Trends on a Periodic Table - Down a group

Answer 16

• I.E. increases down a group
  
  • e^- removed is from a higher energy level
  • nuclear charge increases but the attraction is reduced by the inner electrons which shield the outer ones