electrons, bonding, and structure

Question 1

Explain what is meant by the term relative atomic mass of an element.

Answer 1

• (Weighted) mean/average mass of an atom
• compared with 1/12th mass of carbon-12

Question 2

State two differences between isotopes of the same element and a similarity.

Answer 2

• Different numbers of neutrons
• Different (atomic) masses/mass numbers
• Different physical properties

*Same number of protons and electrons

Question 3

Different isotopes of the same element have the same chemical properties.
Explain why.

Answer 3

same number of electrons in outer shell
OR
same electron configuration OR electron structure

Question 4

State, in words, the 3D shape of an s-orbital and a p-orbital.

Answer 4

• s-orbital is spherical
• p-orbital is dumbbell shaped

Question 5

State the capacity (number of electrons that can fit) of the s, p, d, and f subshells, and how many orbitals each subshell contains.

Answer 5

• s- 2 electrons, 1 orbital
• p- 6 electrons, 3 orbitals
• d- 10 electrons, 5 orbitals
• f- 14 electrons, 7 orbitals

Question 6

What is the principle quantum number, n?

Answer 6

• the shell number OR energy level number

Question 7

Why does the 4s subshell empty/fill before the 3d subshell when ionising, despite having a lower energy level?

Question 8

The reaction of barium with bromine is more vigorous than the reaction of calcium with
bromine.
Explain why.

Answer 8

Atomic radius
* Ba has a greater atomic radius than Ca
* OR Ba has more shells
* OR Ba has more shielding ✓

Attraction
* Nuclear attraction is less in Ba
* OR (outer) electrons in Ba are less attracted (to
nucleus)
* OR Increased distance / shielding in Ba
outweighs increased nuclear charge ✓

Ionisation energy
* Ionisation energy of Ba is less
* OR (outer) electrons in Ba are less attracted (to nucleus)
* OR easier to remove (outer) electrons in Ba ✓

Question 9

Explain why the first ionisation energy of strontium is less than the first ionisation energy of calcium.

Answer 9

Atomic radius

*larger atomic radius
OR
*more shells ✓

Effect of nuclear charge / shielding
*Increased nuclear charge outweighed by
*increased distance / shielding
OR
*more / increased shielding ✓

Nuclear attraction
*less nuclear attraction
OR
*less attraction on electrons ✓

Question 10

Why do successive ionisation energies increase with ionisation number?

Answer 10

radius decreases
AND
attraction between (the remaining) electrons and
nucleus increases

Question 11

Explain the physical properties of silicon, bromine, aluminium, and lithium chloride.

Answer 11

silicone
high melting point- giant covalent lattice requires lots of heat energy to break
cant conduct when molten or solid- no mobile ions that can carry charge.

bromine
low melting point- simple covalent structure and weak induced dipole-dipole forces that dont require lots of energy to break
cant conduct when molten or solid- no mobile ions that can carry charge.

aluminium
high melting point- metallic lattice of rows of cations and delocalised electrons require lots of heat energy to break the attraction between oppositely charged ions
can conduct when molten and liquid- delocalised electrons can carry charge

lithium chloride
high melting point- ionic lattice strong electrostatic forces require lots of heat energy to break
can conduct when molten as there are charged ions that can flow, but not when solid as there aren’t.