Chapter 5

Question 1

How are electrons arranged around the nucleus ?

Answer 1

• electrons are arranged around the nucleus in principle energy levels, or principle quantum shells
• principle quantum numbers(n) are used to number the energy levels or quantum shells, the lower the principle quantity number, the closer the shell is to the nucleus
• each principle quantum number holds a fixed number of electrons 2n^2

Question 2

What are the different subshells of electrons ?

Answer 2

The principle quantum shells are split into sub-shells which are given letters s,p,d and f, only elements with more than 57 electrons have an f shell

The energy of the electrons in the sub-shells increases s < p < d

Question 3

What are orbitals ?

Answer 3

• sub-shells contain one or more atomic orbitals
• orbitals exists at specific energy levels and electrons can only be found at these specific levels, not in between them
• each atomic orbitals can be occupied by a maximum of 2 electrons
• s: 1 orbital
• p: 3 orbitals
• d: 5 orbitals
• f: 7 orbitals

Question 4

What is the shape of the s orbital ?

Answer 4

• the s orbitals are spherical in shape
• the size of the s orbitals are increases with increasing shell number
• the s orbital of the 3rd quantum shell is bigger than the s orbital of the 1st quantum shell

Question 5

What is the shape of the p orbital

Answer 5

• The p orbitals have a dumbbell shape
• every shell has 3 p orbitals except for the first one
• the p orbitals occupy the x,y, z axes and point at right angles to each other, so are oriented perpendicular to each other

Question 6

What does a shell and sub shell look like ?

Answer 6

Question 7

What is electron spin ?

Answer 7

• electrons can be imagined as small spinning charges which rotate around their own axis either clockwise or anticlockwise
• the spin creates a tiny magnetic field with N-S point point up or down
• electrons with the same spin repel each other
• this means electrons will occupy separate orbitals in the same sub-shells first to minimise this repulsion, and spin in the same direction
• they then pair up with the other electron spinning in the opposite direction

Question 8

What is the Pauli exclusion principle ?

Answer 8

• An orbital can only hold 2 electrons and they must have opposite spin, known as Pauli Exclusion Principle
• This is because the energy required to jump to a higher empty orbital is greater than the inter-electron repulsion
• for this reason, they pair up and occupy the lower energy levels first.

Question 9

What is ground state ?

Answer 9

• the ground state is the most stable electronic configuration of an atom which has the lowest amount of energy
• the order of the subshells in terms of increasing energy does not follow a regular pattern.

Question 10

What is the difference between full electron figuration and short hand ?

Answer 10

• the full electron configuration describes the arrangement of all electrons from the 1s subshell up
• the shorthand electron configuration includes using the symbol of the nearest preceding noble gas

Question 11

How is the periodic table split up?

Answer 11

• the periodic table is split into 4 main blocks depending on which orbital the outer most electron is held in

Question 12

What is ionic bonding ?

Answer 12

• ionic bonding involves the transfer of electrons from a metallic element to a non-metallic element
• this creates an electrostatic force of attraction between cations and anions
• once atoms become ions, their electronic configurations are the same as a noble gas

Question 13

What are the physical properties of ionic compounds ?

Answer 13

• melting points are higher for lattices that contain ions with a greater ionic charge
• many ionic compounds will dissolve in polar solvents e.g water

Question 14

How does solubility of ionic compounds work ?

Answer 14

Solubility is dependent on:
1. breaking down the ionic lattice
2. the polar molecules attracting and surrounding the ions
- The δ+ end of the polar molecule can surround the negative anion
- The δ- end of the polar molecule can surround the positive cation
- this breaks the electrostatic forces of attraction between the cation and anion

Question 15

What is covalent bonding ?

Answer 15

• covalent bonds involves the electrostatic attraction between nuclei of 2 atoms and the bonding electrons of their outer shells
• no electrons are transferred but only shared in this type of bonding

Question 16

What is bond energy ?

Answer 16

• The bond energy is the energy required to break one mole of a particular covalent bond in the gaseous states
• the larger the bond energy the stronger the covalent bond it

Question 17

What is bond length ?

Answer 17

• the bond length is the internuclear distance of 2 covalently bonded atoms
• the greater the forces of attraction between electrons and nuclei, the more the atoms are pulled closer to each other
• this decreases the bond length of a molecule and increases the strength of the covalent bond

Question 18

What does a dot and cross diagram look like ?

Answer 18

Question 19

What is an example of expanding the octet rule ?

Answer 19

Question 20

What is dative covalent bond ?

Answer 20

• some molecules have lone pair of electrons that can be donated to form a bond with an electron-deficient atom.
• both the electrons are from the same atom
• this is called dative covalent bonding

Question 21

What is an example of a dative covalent bond ?

Answer 21

• ammonium ion, the H+ ion is electron deficient and has space for 2 electrons in its shell.
• the nitrogen atom has a lone pair which it donates to hydrogen ion.