(U1) Atomic Structure

Question 1

What is atomic number?

Answer 1

The number of protons in the nucleus of an atom

Question 2

What is mass number?

Answer 2

The total number of protons and neutrons in the nucleus of an atom.

Question 3

What is Relative Atomic Mass (RAM) (3)

Answer 3

• The weighted mean mass
• of an atom of an element
• relative to 1/12 of the mass of an atom of carbon-12

Question 4

What is Relative Isotopic Mass (RIM) (3)

Answer 4

• The weighted mean mass
• of an atom of an isotope of an element
• relative to 1/12 of the mass of an atom of carbon-12

Question 5

What are isotopes? (2)

Answer 5

• Atoms which contain the same number of protons
• but a different number of neutrons

Question 6

What is Relative Molecular Mass (RMM) (3)

Answer 6

• The weighted mean mass
• of a molecule
• relative to 1/12 the mass of an atom of carbon-12

Question 7

What is Relative Formula Mass (RFM) (2)

Answer 7

• The weighted mean mass of a species
• relative to 1/12 the mass of an atom of carbon-12

Question 8

What is a molecular ion?

Answer 8

An ion formed by the removal of an electron from a molecule

Question 9

What is First Ionisation Energy? (2)

Answer 9

• The energy required to convert one mole of gaseous atoms
• into gaseous ions with a single positive charge

Question 10

What is Second Ionisation Energy? (2)

Answer 10

• The energy required to convert one mole of gaseous ions with a single positive charge
• into gaseous ions with a double positive charge

Question 11

What is Third Ionisation Energy? (2)

Answer 11

• The energy required to convert one mole of gaseous ions with a double positive charge
• into gaseous ions with a triple positive charge

Question 12

Using a mass spectrometer, how do you calculate relative atomic mass?

Answer 12

(percentage abundance) x (mass charge ratio) / 100

Question 13

What is an orbital? (2)

Answer 13

• a region within an atom that can hold up to 2 electrons
• within opposite spins

Question 14

What shape is an S-type orbital?

Answer 14

Spherical

Question 15

What shape is an O-type orbital?

Answer 15

Dumbbell

Question 16

State Hund’s Rule (2)

Answer 16

• where electrons have choice between orbitals of equal energy
• they will fill the orbitals singly as far as possible

Question 17

State the order of filling for energy levels (up to 9th)

Answer 17

• 1_s
• 2_s
• 2_p, 3_s
• 3_p, 4_s
• 3_d, 4_p

Question 18

Why is 4_s filled before 3_d?

Answer 18

4_s is closer to the nucleus than 3_d

Question 19

In s, p, d, f notation, what do the letters represent?

How many electrons can s, p and d hold?

Answer 19

• Sub shells
• s holds 2, p holds 6, d holds 10

Question 20

What atom does the electronic configuration 1_s² represent?

What does this mean?

Answer 20

• an atom of helium
• the 1st ‘s’ sub shell is filled with 2 electrons

Question 21

State the general equation for 1st ionization energy

Answer 21

X_(g) —> X⁺_(g) + e^-

Question 22

State the general equation for 2nd ionization energy

Answer 22

X⁺_(g) —> X²⁺_(g) + e^-

Question 23

State the general equation for 3rd ionization energy

Answer 23

X²⁺_(g) —> X³⁺_(g) + e^-

Question 24

Why does ionization energy usually increase across a period? (3)

Answer 24

• increased nuclear charge
• Decrease in atomic radius
• same number of shielding electrons

Question 25

What is the electronic configuration of Cr (using noble gas notation)

Why is it irregular?

Answer 25

• [Ar] 3d⁵ 4s¹
• the 4s subshell loses an electron to the 3d subshell to form a half filled subshell (more stable)

Question 26

What is the electronic configuration of Cu (using noble gas notation)

Why is it irregular?

Answer 26

• [Ar] 3d¹⁰ 4s¹
• the 4s subshell loses an electron to the 3d subshell to form a filled subshell (stable)

Question 27

What 2 elements are exceptions to the rule for the filling of orbitals?

Answer 27

• Cu
• Cr

Question 28

Why does ionization energy not increase regularly across a period?

Answer 28

• some have higher than expected energies due to filled and half filled subshells
• transition metals increase marginally due to 3d subshell shielding 4s effectively

Question 29

What happens to 1st ionization energy down a group?

Why?

Answer 29

• decreases
• increase in atomic radius and more energy levels —> more shielding —> attraction weakens

Question 30

What are valence electrons?

Answer 30

Outer electrons

Question 31

How many orbitals are in a:

• p-subshell?
• s-subshell?

Answer 31

• p = 3 orbitals
• s = 1 orbital

Question 32

State and explain the general trend in the first ionization energy across the second period.

Identify and explain any exceptions

(7)

Answer 32

• 1st ionization energy increases left to right
• due to:
  1. increase in nuclear charge
  2. Decrease in distance between nucleus and outer electrons
  3. Same number of shielding electrons
• exceptions: Be and N
• Be —> full outer subshell —> stability —> more energy needed
• N —> half full outer subshell —> stability —> more energy needed

Question 33

When forming cations, which orbital are electrons removed from first in Cr?

Why?

Answer 33

• The 4s subshell
• 4s is further away from the nucleus than 3d