2/12- Atomic Structure Questions

State the number of atomic orbitals in sub levels s, p, d, and f.

s: 1

p: 3

d: 5

f: 7

Arrange the radiations by increasing frequency.

radio waves, microwaves, infrared, visible light, ultra violet, x rays, gamma rays.

Write the electron configuration for Copper (Cu) and Chromium (Cr)

chromium (Cr): [Ar] 4s^1 3d^5

copper (Cu): [Ar] 4s^1 3d^10

Describe how an electron produces a spectrum.

When the electrons are excited, it drops from a higher energy level to a lower energy level which releases photon of visible light.

Describe the emission spectrum of the hydrogen atom, including the relationships between the lines and energy transitions to the first, second and third energy levels.

The lines get closer together at higher frequency/energy. (convergence)

When an electron falls from a higher to a lower energy level in an atom, a photon of light is emitted.

transition to 1st energy level: ultra violet

transition to 2nd energy level: visible light

transition to 3rd energy level: infra red

Describe the structure of an atom.

Atoms contain a positively charged dense nucleus composed of protons and neutrons (nucleons). Negatively charged electrons occupy the space outside the nucleus.

What device is used to determine the relative atomic mass of an element from its isotopic composition?

the mass spectrometer

Define electromagnetic spectrum.

the different types of electromagnetic waves.

.

The line emission spectrum of hydrogen provides evidence for the existence of electrons in discrete energy levels, which converge at higher energies.

What is a more detailed model of the atom?

A more detailed model of the atom describes the division of the main energy level into s, p, d and f sub-levels of successively higher energies.

Sub-levels contain a fixed number of orbitals, regions of space where there is a high probability of finding an electron.

Order the color of visible wavelength from the shortest to longest wavelength.

violet indigo blue green yellow orange red

What is the relationship between the lines and energy transitions to the first, second and third energy levels?

.

Define isotope.

Atoms that contain the same number of protons but different number of neutrons.

Describe the energy levels and sub levels in detail.

The main energy level or shell is given an integer number, n, and can hold a 2 maximum number of electrons, 2n^2 . The periods indicate the main energy level of an atom.

A more detailed model of the atom describes the division of the main energy level into s, p, d and f sub-levels of successively higher energies.

Sub-levels contain a fixed number of orbitals, regions of space where there is a high probability of finding an electron.

Each orbital has a defined energy state for a given electronic configuration and chemical environment and can hold two electrons of opposite spin.

Describe the relationship between colour, wavelength, frequency and energy across the electromagnetic spectrum.

The shorter the wavelength, the higher the frequency of an electromagnetic spectrum.

In visible light, violet has the shortest wavelength (highest frequency) while red color has the longest wavelength (lowest frequency)

Explain how the Bohr's model contributed to the explanation of line spectra.

Bohr proposed a model in which electrons orbit the nucleus and only exist in certain allowed energy levels. He then used this model to explain the line spectra of hydrogen and other elements.

State the meaning of the term mass number (A). State the difference between mass number and atomic number (Z). Show hoe these numbers can be used to determine the number and types of particles in an atom.

mass number: the sum of number of protons and neutrons in the nucleus.

atomic number shows only the number of protons.

Can be used to find numbers of protons, neutrons, and electrons:

number of electrons = number of protons (Z)

number of neutrons = A - Z.

Identify a radioisotope carbon and state one of its uses.

C-14 and C-11:

used as tracers in medical/scientific tests.

Distinguish between a continuous spectrum and a line spectrum.

Continuous spectrum has radiation spread over all /wavelengths/frequencies/energies/colors

Line spectrum only has radiation absorbed or emitted at specific colors/wavelengths/frequencies.

State why some radioisotopes (like Co-60 e.g.) is used in radio therapy.

They can emit penetrating gamma radiation/rays

Define the term relative atomic mass.

Ratio of AVERAGE mass of an atom to 1/12 the mass of a Carbon 12 isotope.

Compare and contrast the physical and chemical properties of different isotopes of an element.

Different physical properties (due to different masses):

-melting points

-boiling points

-density

Same/similar chemical properties (due to same # of valence electrons)

-reactivity

Describe the appearance of the emission spectrum of hydrogen. Explain how this spectrum is related to the electron energy levels of hydrogen.

It is a line spectrum.

The lines converge at high energy/high frequency/shorter wave length/blue end of spectrum

Each transition is related to the energy difference of electron transition between energy levels.

Explain why metals are good conductors of electricity and why they are malleable.

metals have delocalized electrons / sea of electrons which are mobile/can move / OWTTE;

layers/positive ions/cations/atoms slide past/over each other / OWTTE;

Do not accept nuclei for M2.

Explain why:

1. calcium has a higher melting point than potassium.

2. sodium oxide has a higher melting point than sulfur trioxide.

1. calcium ionic charge is twice/greater than the potassium ionic charge / calcium has more delocalized electrons than potassium;

greater attraction of delocalized electrons and Ca2+/ less attraction between the delocalized electrons and K+

Do not accept calcium ion has a 2+ without comparison to K+

2. Na2O ionic/(stronger electrostatic) attractions between Na+ and O2−;

SO3 has (weak) intermolecular/van der Waals'/London/dispersion/dipoledipole attractions;

intermolecular/van der Waals'/London/dispersion/dipole-dipole forces are weaker/more easily broken than (strong) ionic bonds / ionic bonds are stronger/harder to break than intermolecular bond/van der Waals'/London/dispersion/dipole-dipole forces;

Define orbitals.

Regions of space where there is a high probability of finding an electron.

Describe and explain the evidence for ionization energy.

In a hydrogen emission spectrum, the emission spectrum converge at the blue end (short frequency) end.

Eventually, at the convergence limit, the lines merge to form a continuum. Beyond this point the electron can have any energy and so must be free from the influence of the nucleus, i.e. the electron is no longer in the atom. Knowing the frequency of the light emitted at the convergence limit enables us us to work out the ionisation energy of an atom

In an emission spectrum, the limit of convergence at higher frequency corresponds to the first ionization energy, because the ionisation energy is the minimum amount of energy required to remove an electron from a gaseous atom.

State the equation for calculating ionization energy.

The ionization energy of an atom can be calculated using the frequency (or wavelength) of the convergence limit using equation:

E=hv

E: energy

h: Planck's constant

v: frequency

**remember to convert calculated ionization energy for a SINGLE ATOM to mols, and then the required unit.

Explain the trend of ionization energy as more electrons are removed.

The highest energy electrons are removed first. The second ionisation energy is always higher than the first, and this can be explained in two ways:

1. Once an electron has been removed from an atom, a positive ion is created. A positive ion attracts a negatively charged electron more strongly than a neutral atom does. More energy is therefore required to remove the second electron from a positive ion.

2. Once an electron has been removed from an atom, there is less repulsion between the remaining electrons.They are therefore pulled in closer to the nucleus. If they are closer to the nucleus, they are more strongly attracted and more difficult to remove.

By looking to see where the first large jump occurs in successive ionization energies one can determine the number of valence electrons (and hence the group in the periodic table to which the element belongs).

This trend in first ionization energy across periods account for the existence of main energy levels and sub-levels in atoms.

Since this is called successive ionization energy and energy main and sub levels are presented by electron configuration, successive ionization energy data for an element give information that shows relations to electron configurations.

Explain the trends and discontinuities in first ionization energy across a period.

The successive ionization energy graph will show that there are certain points where there is a large jump, and the graph will continue to increase gradually until it meets the next "jump" again.

The "jump" indicates a transition of main energy levels from a higher energy level to a lower energy level, while the gradual increase gives evidence to sub energy levels within main energy levels.

Discuss the origin of resonance bonds in ozone.

lone pair on p orbital «of O atom» overlaps/delocalizes with pi electrons «from double bond»

both O-O bonds have equal bond length

OR

both O-O bonds have same/1.5 bond order

OR

both O-O are intermediate between O-O AND O=O

both O-O bonds have equal bond energy

Accept "p/pi/ππ electrons are delocalized/not localized".

[3 marks]