Topic 2: Atomic Structure

Question 1

what is an element?

Answer 1

a substance that cannot be broken down into simpler substances by a chemical reaction

Question 2

Daltons Model of an Atom

Answer 2

• all matter is composed of atoms
• atoms cannot be created or destroyed
• atoms of the same element are alike
• atoms of different elements are different
• atoms combine to form molecules

Question 3

what is a compound?

Answer 3

a substance made by chemically combining two or more elements. It has different properties than its constituent elements

Question 4

Rutherford’s model of an Atom

Answer 4

• fired alpha particles at a piece of gold foil; some bounced back
  = atoms are mainly empty space and contain a positive nucleus

Question 5

Proton

Answer 5

+1, in nucleus

Question 6

Electron

Answer 6

-1, outside of nucleus (space outside)

Question 7

Neutron

Answer 7

0, in nucleus

Question 8

Mass Number (Ar)

Answer 8

number of protons plus number of neutrons in an atom

Question 9

Isotopes

Answer 9

atoms of the same element with different mass numbers due to number of neutrons it contains (same electrons and protons however)

Question 10

Relative average mass formula

Answer 10

total mass/number of atoms

Question 11

positive ion

Answer 11

when an element loses an electron (cation)

Question 12

negative ion

Answer 12

when an element gains an electron

anion

Question 13

Relative Atomic Mass

Answer 13

weight mean of all naturally occuring isotopes of an element relative to carbon-12

Question 14

decreasing wave frequencies/energy

Answer 14

Y-Rays
X-Rays
UV Radiation
Visible light
R Radiation 
Microwaves
Radio waves

Question 15

Continious spectrum

Answer 15

contains radiation of all wavelengths within a given range

e.g. visible light

Question 16

Line spectrum

Answer 16

discrete lines of different wavelengths and frequencies

e.g. emmision or absorbtion spectra

Question 17

Explain emmision spectrum of hydrogen atom

Answer 17

• The emission spectrum of hydrogen atom consists of different series of lines in different regions of the
electromagnetic spectrum.
• The lines in an emission spectrum are produced by excited electrons falling from higher to lower energy
levels: ΔEatom = hν = hc/λ.
• As the energy levels of the hydrogen atom converge at higher energy as they are further from the nucleus,
the lines in the spectrum also converge at higher energy/frequency.

• 2–>1 is the UV series
• anything to 2 is the visible light series (palmer)

Question 18

Formula/relation between frequency and wavelength

Answer 18

• Frequency (ν) and wavelength (λ) are related by: c (speed of light) = ν λ.
• The energy of a photon (Ephoton) is related to the frequency (ν) of the radiation by Planck’s equation:
Ephoton = hν (the equation is given in section 1 of the IB data booklet)
h is Planck’s constant (see section 2 of the IB data booklet)

Question 19

frequency

Answer 19

the number of waves that pass a certain point

Question 20

IR Radiation

Answer 20

• long wavelength; short frequency; low energy

Question 21

UV radiation

Answer 21

• short wavelength, high frequency, high energy

Question 22

how is a line spectrum produced

Answer 22

when white light is passed through hydrogen gas

Question 23

how is an emmision spectra produced

Answer 23

by providing hydrogen gas with high voltage

Question 24

first ionization energy

Answer 24

minimum energy needed to remove one mole of electrons from one mole of gaseous atoms in their ground state

Question 25

main energy levels of an atom and their energies?

Answer 25

• higher energy states= exicted electrons
• falling to ground state from high energy level has high energy

N= 1 (ground state)
N=2
N=3
N= infinity

Question 26

how are lines the emission spectra produced

Answer 26

The lines in an emission spectrum are produced by excited electrons falling from higher to lower energy
levels: ΔEatom = hν = hc/λ.

Question 27

Heisenbergs Uncertainty principle

Answer 27

• We cannot know where an electron of an atom is at a given time, so we use ‘probable diagrams’

Question 28

Shrodigers model of the hydrogen atom

Answer 28

• atomic orbitals

- wave equation describes properties/behaviour of an electron

Question 29

atomic orbital

Answer 29

• region around nucleus where there is a 90% probably of finding an electron
• different levels
• higher energy; more likely to find an electron further way from nucleus

Question 30

Orbitals

Answer 30

Orbitals are regions in space in which an electron
may be found in an atom. Each orbital can hold two
electrons of opposite spin.

Question 31

orbital shapes

Answer 31

s orbitals are spherical and 
p orbitals are dumb-bell shaped. 
There
are three p orbitals orientated along the x, y and z
axis.

Question 32

Pauli exclusion principle

Answer 32

states that only electrons with opposite spin can occupy the same orbital.

Question 33

Orbital diagrams

Answer 33

• used to describe the number of electrons in each orbital.
• Each orbital is represented by a box and each electron by a single-headed arrow which represents the direction of its spin.

Question 34

energy levels

Answer 34

Each main energy level can hold a maximum of 2n^2
electrons.
• Each main energy level contains n sub-levels and n2
orbitals.

Question 35

Aufbau principle

Answer 35

states that orbitals with lower energy are filled before

those with higher energy.

Question 36

aufbau order

Answer 36

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4f, 5d, 6p, 7s …