Atomic Theory Sample exam questions

Question 1

Define atomic orbital

Answer 1

Region of space around the nucleus where electrons are most likely to be found

Question 2

Define first ionisation energy

Answer 2

The minimum energy required to remove most loosely bound electron from a neutral gaseous element in its ground state

Question 3

Explain general increase in first ionisation energy across a period

Answer 3

• Increases across
• Decreasing atomic radius
• Increase in effective nuclear charge
• Screening effect remains the same

Question 4

Define Atomic number

Answer 4

Number of protons in the nucleus of an atom

Question 5

Define atomic mass

Answer 5

Number of protons and neutrons in the nucleus of an atom

Question 6

Define Relative atomic mass

Answer 6

The average mass of an atom compared to 1/12th the mass of the carbon 12 isotope

Question 7

Define electronegativity

Answer 7

The measure of the attraction that an atom has for the shared pair of an electron in a covalent bond

Question 8

Describe how electronegativity values can be used to predict the type of bonds that occur between a pair of atoms

Answer 8

<0.4= pure covalent bond
>0.4 but <1.7=polar covalent bond
>1.7= ionic bond

Question 9

explain the trend of atomic radius down the group

Answer 9

• Increases
• nuclear charge increases
• screening effect increases

Question 10

explain why alkali metals are so reactive

Answer 10

• Group one
• 1 electron in its outer energy level
• it loses that one electron to follow the octet rule

Question 11

Explain why alkali metals become more reactive down the group

Answer 11

• atomic radius increases down the group

Question 12

Explain why bromine is less reactive than chlorine

Answer 12

• The electronegativity of Bromine is smaller

- The atomic radius is larger than chlorine

Question 13

Explain why neon is chemically inert

Answer 13

8 electrons in its outside shell

Question 14

How is an ionic bond formed between a pair of atoms

Answer 14

• Electrons are transferred to form a positive ion

- To form a negative ion

Question 15

How is a double covalent bond formed between a pair of atoms

Answer 15

The sharing of 2 pairs of electrons

Question 16

transition metal

Answer 16

one that forms an ion with an incomplete d-subshell

Question 17

Give 2 characteristic properties of transition metals

Answer 17

variable valency

acts as a catalyst

Question 18

what is a crystal

Answer 18

solid with a repeating pattern of atoms

Question 19

Describe the bonding in a metallic crystal

Answer 19

positive ions with valence electrons being shared

Question 20

would you expect nickel to be a good electrical conductor, why?

Answer 20

yes

electrons are free to move

Question 21

Account for the visible lines in the hydrogen emission spectrum

Answer 21

• Electrons occupy the ground state
• they move to excited energy levels due to heat or electricity
• it’s unstable and falls back down
• light is released

Question 22

Why is there a sharp increase from the 11th to the 12th ionisation energy

Answer 22

12th electron is taken from a new energy level which is closer to the positive nucleus

Question 23

Intermolecular forces

Answer 23

forces that exist between molecules

Question 24

Name the type of intermolecular force between

i) ammonia gas
ii) water
iii) methane gas

Answer 24

i) hydrogen bonds
ii) hydrogen bonds
iii) van der Waals forces

Question 25

explain in terms of intermolecular forces why the NH3 is very soluble in water

Answer 25

- water and ammonia are both polar molecules - one side of each is slightly negative and the other side is positive - hydrogen bonds can form between them and ammonia dissolves - "like dissolves like"

Question 26

Relative atomic mass

Answer 26

The average mass of one element compared to 1/12th the carbon 12 isotope

Question 27

Why do electronegative values decrease across a period

Answer 27

- nuclear charge increases - electrons enter the same energy level - screening effect stays the same - Electronegativity values decrease as the atomic radius increases

Question 28

Covalent crystal bonding

Answer 28

Each carbon atom forms four covalent bonds with four more carbon atoms

Question 29

What are the bonding forces in an ionic crystal

Answer 29

Ionic bonds

Question 30

What are bonding forces that hold molecular crystals together

Answer 30

Intermolecular forces

Question 31

Explain why the molecular crystals usually have lower melting points than ionic crystals

Answer 31

Intermolecular bonds in molecular crystals are weaker than ionic bonds which are easier to break

Question 32

What type of crystal is characterised by a solid having a lustre and very high mobility of electrons throughout the structure

Answer 32

Metallic

Question 33

Atomic Number

Answer 33

Number of protons in an atom of a nucleus

Question 34

First ionisation energy

Answer 34

The minimum energy required to remove the most loosely bound electron from a neutral gaseous element in its ground state

Question 35

A general increase in ionisation energy

Answer 35

- Nuclear charge is increasing - Atomic radius is decreasing - Screening effect stays the same

Question 36

why is there a lot of energy required to ionise a neon atom

Answer 36

Neon is a noble gas It has 8 electrons in its outer shell It is stable and does not want to lose an electron

Question 37

Why is the first ionisation energy of xenon higher than neon

Answer 37

Xenon has a larger atomic radius than neon

Question 38

Define atomic orbital

Answer 38

A region in space around the nucleus where electrons are most likely to be found

Question 39

What's the difference between the 2s and 2p orbitals of neon

Answer 39

S is lower in energy than the P orbital | Px, Py, Pz orbitals differ in direction

Question 40

Why do electron pairs repel each other

Answer 40

Like charges repel | Electrons are negatively charged so they repel each other at an energy level

Question 41

Compare the magnitude of repulsion between the two lone pairs and repulsion between two bonding pairs of electrons

Answer 41

Repulsion between two lone pairs of electrons is greater than the repulsion between two bond pairs Lone pairs of electrons are closer to the nucleus than bond pairs

Question 42

Distinguish between ground and excited state

Answer 42

Ground: electrons occupy the lowest available energy level Excited: Electrons occupy a higher energy level

Question 43

2 Ways an electron can become excited

Answer 43

Heat | Electricity

Question 44

Why is there no yellow line in the hydrogen emission spectrum

Answer 44

No transition equal in energy to produce a yellow line | Electrons cant occupy spaces between energy levels

Question 45

Describe how you carried out a flame test

Answer 45

- Soak a wooden splint in water - dip in salt - place splint into the blue flame of a bunsen burner

Question 46

Define mass number

Answer 46

Number of neutrons and protons in an atom of a nucleus

Question 47

Define relative atomic mass

Answer 47

Mass of an atom of an element compared to 1/12th the carbon-12 isotope

Question 48

Define electronegativity

Answer 48

The measure of the force of attraction of an atom in a molecule for the shared pair of electrons in a covalent bond

Question 49

Identify a type of bond in a water molecule

Answer 49

Polar covalent bond

Question 50

Predict solubility of methane

Answer 50

Methane is not soluble in water water is polar methane is non-polar Like dissolves like