Atomic Structure

Question 1

Define elements

Answer 1

The simplest substances, made up from simple particles.
Consist of atoms which are all the same (as single atoms, He, or bonded together, O2).

Question 2

Define molecules

Answer 2

More than one atom bonded together (can be the same/different).

Question 3

Define compounds

Answer 3

Combinations of different types of atom e.g. CO2.

Pure = two or more elements chemically combined.

Question 4

Define pure substance

Answer 4

Made of only one type of particle.

Question 5

Define atom

Answer 5

The smallest part of an element that can exist chemically (but not the smallest particles).

Question 6

Define atomic number

Answer 6

The number of protons in the nucleus of an atom.

Question 7

Define relative atomic mass

Answer 7

The sum of the number of protons plus neutrons in the nucleus of an atom.

Question 8

Define isotope

Answer 8

Atoms of the same element with different numbers of neutrons.

Question 9

Define a mole

Answer 9

Mass of a substance containing 6 x 10^23 atoms (or particles).

Question 10

Define electron, what is strange about them?

Answer 10

Subatomic particles with an electric charge of -1.
Demonstrate wave particle duality.

Question 11

Define atomic orbital

Answer 11

Region around an atom in which there is a high probability of finding an electron/pair of electrons.
Region of space defined by a wavefunction.

Question 12

What did John Dalton propose in 1803?

Answer 12

The solid sphere model.
Based on the Ancient Greek idea that atoms are indivisible.
Atoms of a given element are identical.

(Compounds = combinations of different types of atoms).

Question 13

What did J.J Thomson propose in 1904?

Answer 13

Plum pudding model.
After his discovery of electrons in 1897.
Atom composed of electrons scattered throughout a spherical cloud of positive charge.

Question 14

What did Ernest Rutherford propose in 1911?

Answer 14

Nuclear model.
Fired positive alpha particles at gold foil, only some deflected at large angles (most passed through with little deflection).
Concluded atom mostly empty space with positive charge concentrated in central nucleus.

Question 15

What did Niels Bohr propose in 1913?

Answer 15

Planetary model.
Electrons moved around nucleus in orbits of fixed sizes and energies but electron energy quantised (limited to specific energy values).

Question 16

What did Erwin Schrodinger propose in 1926?

Answer 16

Quantum model.
Electrons move in waves, impossible to know exact locations of electrons but have clouds of probability = orbitals where electrons are likely to be found.

Question 17

What do atoms of the same element have in common?

Answer 17

All have the same number of protons in their nucleus (atomic number).

Question 18

Give the symbols for protons, neutrons and electrons.

Answer 18

p, n , e

Question 19

Give the masses of p, n and e.

Answer 19

p = 1.673 x 10^-27 kg
n = 1.675 x 10^-27kg
e = 9.109 x 10^-31kg

Question 20

Give the charges of p, n and e.

Answer 20

p = +1
n = 0
e = -1

Question 21

Why are moles used?

Answer 21

A mole of atoms is easier to weigh compared to a single atom.

Question 22

In terms of moles what does relative atomic mass report on?

Answer 22

The mass of a mole of atoms e.g. 6 x 10^23 carbon atoms weigh 12.011g

Question 23

Give units for relative atomic mass (solids and liquids).

Answer 23

gmol^-1
molL^-1

Question 24

What did Schrödinger suggest the behaviour of electrons in atoms could be explained by?

Answer 24

Properties of waves.

Question 25

What is a wavefunction?

Answer 25

Describes electrons in particular orbit.
An equation to model movement of an electron in an atom.

Question 26

What is the current model of the atom?

Answer 26

A nucleus surrounded by a cloud of electron density.

Question 27

How are electrons arranged in atoms?

Answer 27

In successive principal energy levels/shells.
1st shell is closest to nucleus.
Each shell is split into smaller sublevels (s, p, d, f).
Each subshell split into smaller atomic orbitals.
Each atomic orbital holds a maximum of 2 electrons.
Orbitals have direction represented by cartesian axes: x, y and z.

Question 28

How many electrons are in principal quantum number 1?
Give the subshells and atomic orbitals.

Answer 28

Electrons: 2
Subshells: 1s
Atomic orbitals: 1s

Principle quantum number - describes the energy of an electron and the most probable distance of the electron from the nucleus.

Question 29

How many electrons are there in principle quantum number 2?
Give the subshells and atomic orbitals.

Answer 29

Electrons: 8
Subshells: 2s, 2p
Atomic orbitals: 2s, 2px, 2py, 2pz (subscript)

Question 30

How many electrons are there in principle quantum number 4?
Give subshells and atomic orbitals.

Answer 30

Electrons: 32
Subshells: 4s, 4p, 4d, 4f
Atomic orbitals: 4s, 4px, 4py, 4pz, 4dxy, 4dxz, 4dyz, 4dx^2-y^2, 4dz^2, seven f orbitals

Question 31

How many electrons are there in principle quantum number 3?
Give subshells and atomic orbitals.

Answer 31

Electrons: 18
Subshells: 3s, 3p, 3d
Atomic orbitals: 3s, 3px, 3py, 3pz, 3dxy, 3dxz, 3dyz, 3dx^2-y^2, 3dz^2

Question 32

Describe s orbitals. Give details about:
- shape
- how many orbitals there are
- principal quantum number(s) found at
- the number of electrons each orbital holds

Answer 32

Spherical - symmetrical about all three axes.
One s orbital.
Found at all principal quantum numbers.
Hold a maximum of two electrons.

Question 33

Describe p orbitals. Give details about:
- shape
- how many orbitals there are
- principal quantum number(s) found at
- the number of electrons each orbital holds

Answer 33

Identical in shape (dumbbell) and point in different directions.
Three p orbitals
Found at principle quantum number 2 and above.
Each orbital holds a maximum of 2 electrons.

Question 34

Describe d orbitals. Give details about:
- shape
- how many orbitals there are
- principal quantum number(s) found at
- the number of electrons each orbital holds

Answer 34

Complicated shape (double dumbbell).
Five d orbitals.
Found at principle quantum number 3 and above.
Each orbital holds a maximum of 2 electrons.

Question 35

Describe f orbitals. Give details about:
- shape
- how many orbitals there are
- principal quantum number(s) found at
- the number of electrons each orbital holds

Answer 35

Very complicated shape.
Seven f orbitals.
Found at principle quantum number 4 and above.
Each orbital holds a maximum of 2 electrons.

Question 36

What is meant by orbitals being degenerate?

Answer 36

They have equal energies.

Question 37

List 3 electron configuration rules.

Answer 37

1. Pauli exclusion principle
2. The Aufbau principle
3. Hund’s rule of maximum multiplicity

Question 37

What does the Pauli exclusion principle state?

Answer 37

Each orbital contains a maximum of 2 electrons and for 2 electrons to occupy one orbital, the spins must be paired/opposite.

(Clockwise rotation around the axis of the electron represented by up arrow and anticlockwise represented by down arrow).

Question 38

What does Hund’s rule of maximum multiplicity state?

Answer 38

Electrons occupy a set of degenerate energy orbitals by keeping their spins parallel.
An atom in the ground state adopts a configuration with the greatest number of unpaired electrons.

(Ground state = the lowest possible energy an atom can have)

Question 38

What does the Aufbau principle state?

Answer 38

Electrons occupy the lowest energy vacant orbital.

Question 38

How many blocks is the periodic table comprised of?

Answer 38

Four - s, p, d, f.

Question 39

How is each block named?

Answer 39

For the orbital in which the ‘last’ electron resides.