Exam Q 24

Question 1

Distinguish between ground state and excited state for the electron in a hydrogen atom

Answer 1

The ground state of an atom is one in which the electrons occupy the lowest available energy level (n=1)

The excited state of a hydrogen electron is when the electron occupies higher energy levels than those available in the ground state e.g n<1

Question 2

How can the electron in a hydrogen atom become excited?

Answer 2

it gains energy by heating

Question 3

Explain the origin of the series of visible lines in the emission spectrum of hydrogen

Answer 3

Electrons fall back down from higher energy levels to n=2

The energy lost is emitted as different frequencies of light

Question 4

What is the name of the visible line spectrum for hydrogen?

Answer 4

Balmer series

Question 5

Explain why there is no yellow line in the hydrogen emission spectrum

Answer 5

There is no corresponding electron transition for yellow. No electron can exist between energy levels

Question 6

Describe how to carry out a flame test to confirm the presence of lithium in a salt sample

Answer 6

Soak wooden splints in water or a platinum wire in concentrated hydrochloric acid for 24 hours.
Pick up some of the salt sample on a wooden splint and place it over a flame of a bunsen burner.
Note that if the colour of the flame is crimson then lithium is present in the salt sample.

Question 7

Define an atomic orbital

Answer 7

It is the region in space where there is a high probability of finding an electron

Question 8

Distinguish between a 2p orbital and a 2p sublevel.

Answer 8

2P orbital:
Draw 1 dumbell.
Draw box with one arrow up and one arrow down

A 2P orbital can only contain 2 electrons

P sublevel:
Draw x,y,z dumbell orbitals and label.
Draw 3 boxes with one arrow up and one arrow down

A 2P sublevel contains 3 2p orbitals that all contain 2 electrons each

Question 9

Write the s, p electron configuration for a calcium atom

Answer 9

1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2

1s22s22p63s23p64s2

Question 10

Explain in terms of energy sublevels why the arrangement of electrons in the main energy levels in a calcium atom is 2, 8, 8, 2 and not 2, 8, 10

Answer 10

The 4s sublevel is lower in energy than the 3d sublevel/ electrons fill the 4s before the 3d sublevel