Electron Arrangement

Question 1

The arrangement of electrons around the nucleus was studied by…………

Answer 1

Niels Bohr(1922)

Question 2

What is a continuous spectrum?

Answer 2

It is when white light passes through a prism, and the white light is broken up into an array of colours

Question 3

What is line spectrum

Answer 3

It is when light from a hydrogen discharge tube is passed through a prism, a series of narrow coloured lines are formed

Question 4

What is a hydrogen discharge tube?

Answer 4

Glass tube filled with gas at low pressure with an electric current running through it.

Question 5

Differentiate between a spectrometer and a spectroscope

Answer 5

A spectrometer is a device used to carry out measurements on spectra, while spectroscopes are simply used to observe spectra

Question 6

What colours do the following salts of metals give when burned

Sodium

Potassium

Lithium

Barium

Copper

Strontium

Answer 6

Yellow

Lilac

Crimson

Green

Blue/Green

Red

Question 7

What is an energy level?

Answer 7

It is the fixed energy value that an electron in an atom may have

Question 8

What is the ground state?

Answer 8

It is where electrons occupy the lowest available energy levels

Question 9

What is the excited state?

Answer 9

It is where electrons occupy higher energy levels than those in the ground state

Question 10

Explain Bohr Theory

Answer 10

1. An electron occupies fixed energy levels
2. At its ground state it occupies the lowest available energy levels
3. It can jump to a higher energy level if it receives a certain amount of energy
4. Energy absorbed must exactly equal the energy difference between ground state and excited state according to E2-E1=hf
5. Because the excited state is unstable the electron falls back to ground state
6. It emits the excess energy in the form of a photon of light (hf)

Question 11

Name the three series

Answer 11

Balmer series- in the visible spectrum so we can see li es

Paschen- in infrared region

Lyman- in the ultraviolet region

Question 12

What are the limitations of the Bohr Theory

Answer 12

1. It only applied to electrons in the hydrogen atom
2. Doesn’t take wave like motion into account
3. Doesn’t take sub levels into account
4. Doesn’t take the Uncertainty Principle into account

Question 13

How do lines on emission spectrum provide evidence for existence of energy levels

Answer 13

1. Lines on emission spectrum are produced when an electron falls from the excited state to the ground state
2. The line is the light energy produced when it calls
3. The light energy is the difference between the energy levels so shows the existence of energy levels.

Question 14

What is Atomic Absorption Spectrum

Answer 14

Atomic absorption measures the amount of light at a resonant wavelength, which passes through a cloud of atoms and is absorbed by them

When white light is passed trough a sample of gas and then a prism, the light that emerges will have certain wavelengths missing. This spectrum is called Atomic Absorption Spectrum

Question 15

Name some some uses of Atomic Absorption Spectrum

Answer 15

1. Used to identify unknown gas samples
2. Detects concentration of an element present a light source of that element must be used
3. The intensity of light before and after the sample is measured and this difference equals the concentration of the element present
4. Used to measure the amount of lead in a sample of water

Question 16

Name the different energy sub levels

Answer 16

1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, 5s, 5p, 4d, 4f, 5s, 5p, 5d, 5f, 6s, 6p, 6d, 6f, 7s, 7p, 7p, 7d, 7f

Question 17

Define an energy sub level

Answer 17

An energy sublevel is a sub division of a main energy level and consists of one or more orbitals of the same energy

Question 18

What was Louis De Broglie’s contribution

Answer 18

All moving particles have a wave associated with them, this proved that electrons do not travel in precise paths.

Question 19

What is Heisenberg’s Uncertainty Principle

Answer 19

It is impossible to measure at the same time both the velocity and position of an electron

Question 20

What is an orbital

Answer 20

An orbital is a region in space within which there is a probability of finding an electron

Question 21

What is Schrodinger’s contribution

Answer 21

Used mathematical equations to work out the probability of finding an electron in any sub level

Question 22

What shape is the S orbital

Answer 22

Spherical

Question 23

What shape is the P orbital

Answer 23

It is a dumb bell

Question 24

How many electrons are in s, p, and d energy levels respectively

Answer 24

2, 6, 10

Question 25

list all the energy levels available for the first 36 elements in the periodic table

Answer 25

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p

Question 26

How are Balmer series lines formed

Answer 26

They are formed when one set of electron transitions from higher levels to the level where n = 2 gives rise to the lines in the visible spectrum.

Question 27

What implications did De Boglie’s theory on the wave nature of the electron have on Bohrs Theory

Answer 27

If the electron has a wave motion, then Bohr’s picture fit travelling in a precise path at a precise distance from the nucleus cannot give q full picture of the situation