Structure of the Atom

Question 1

Nucleus

Answer 1

• Nucleus of an atom contains protons and neutrons
• mass of proton = mass of neutron
• protons are positive and neutrons are neutral
• collectively known as nucleons

Question 2

Atomic Number (Z)

Answer 2

• the number of protons in an atom

- In a neutral atom, the number of protons = the number of electrons

Question 3

Mass Number (A)

Answer 3

• the number of protons and neutrons

- No. of neutrons (N) can be determined by N=A-Z

Question 4

Representation of Atoms

Answer 4

Check book

Question 5

Isotopes

Answer 5

• Isotopes are different atoms of the same element with the same atomic number but different mass numbers
• eg. 24/12Mg and 25/12Mg are isotopes of Mg

Question 6

Relative Atomic mass, Ar

Answer 6

The relative atomic mass (Ar) is a number that compares the average mass of an atom with the mass of the C-12 atom taken to be 12 units.
*Check notes for calculations

Question 7

Energy Level Diagrams

Answer 7

NB opposite spin in orbitals, check notes.

Question 8

Valence electrons

Answer 8

• The electrons that occupy the outermost energy level of an atom
• electrons involved in bonding
• No. of valence electrons = group number

Question 9

Core electrons

Answer 9

• Electrons that occupy the inner energy levels are known as core electrons
• NB because they shield the valence electrons from the attraction of the positive nucleus

Question 10

Atomic Diameter

Answer 10

• How far electrons are positioned from the centre (Nucleus) determines size of atom
• The radius of an atom can only be found by measuring the distance between the nuclei of two touching atoms, then halving that distance

Question 11

Ionisation energy

Answer 11

• 1st ionisation energy = energy required to remove first electron and so on
• Valence first, feel attraction the least
  Factors that effect IE:
• Atomic radius (smaller atoms = higher FIE)
• Charge (Higher positive charge = harder to remove)

Question 12

Ionisation energy Pt.2

Answer 12

• As you move across a period, 1st IE increases due to nuclear charge increasing, but valence E all in same energy level = atomic radius decreases, harder to remove
• As you move down a group, 1st IE decreases due to extra energy level being added, but all atoms have same valence E’s increasing shielding effect