Q8s

Question 1

Define Atomic Number?

Answer 1

Number of protons (in an atom of an element or in nucleus of an atom).

Question 2

Define Mass Number?

Answer 2

Number of protons and neutrons (in an atom of an element).

Question 3

Define relative atomic mass?

Answer 3

Mass of an atom of an element relative to 1/12 the mass of C12 isotope.

Question 4

How does an electron in an atom become excited?

Answer 4

It gains energy or heat for example by electricity or a flame.

Question 5

Why does the electron not remain in the excited state?

Answer 5

It is unstable. Loses energy.

Question 6

Define energy level?

Answer 6

It’s the amount of energy that an electron in an atom has.

Question 7

Distinguish between the ground and an excited state?

Answer 7

The ground state electron is in the first energy or the lowest energy level before energy supplied. In the excited state, the electron has been given energy or heat and is promoted to a higher energy level.

Question 8

What happens when an electron in an excited state in an atom falls to a lower energy state?

Answer 8

Light is emitted.

Question 9

What is the relationship between the energy of an excited energy level, the lower energy level and the frequency of the electromagnetic radiation emitted?

Answer 9

E2-E1 = hf, where E1 is the energy of electron in lower energy level, E2 is the energy of electron at higher energy level (excited state), f = frequency of photon, and h = Planck’s constant.

Question 10

State and explain the trend in atomic radii down group 1 in the periodic table?

Answer 10

Atomic radii increases down group 1 as additional shells are added.

Question 11

Define atomic Orbital.

Answer 11

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

Question 12

What is the maximum number of electrons that can occupy any atomic orbital?

Answer 12

2

Question 13

How do 2p atomic orbitals differ from one another?

Answer 13

They have different directions in space.

Question 14

What is the difference between s and p orbitals?

Answer 14

S orbital is spherical and holds a max of 2 electrons. P orbital is dumbbell-shaped and holds up to 6 electrons.

Question 15

Define Isotopes?

Answer 15

Same atomic number, different mass number.

Question 16

Why are alkali metals so reactive?

Answer 16

They have only one electron in their outer shell.

Question 17

Why do alkali metals become more reactive down their group in the periodic table?

Answer 17

The atomic radius increases, so the outer electrons are further from the nucleus and more loosely bound.

Question 18

Why is Bromine less reactive than chlorine?

Answer 18

Bromine has a lower electronegativity; its nucleus is further from the outer electrons.

Question 19

Why is Neon chemically inert?

Answer 19

It has a full octet of electrons, giving it a stable electronic configuration.

Question 20

What is meant by the first ionisation energy of an element?

Answer 20

It is the minimum energy required to remove the most loosely bound electron from one mole of a neutral gaseous atom.

Question 21

Why are ionisation values of some elements higher than expected?

Answer 21

They have a stable configuration with a full or half-filled outer shell.

Question 22

Explain the general increase in first ionisation energy values across the second period of the periodic table.

Answer 22

It is due to increasing nuclear charge and decreasing atomic radius.

Question 23

Explain the general trend in first ionisation energy values down any group of the periodic table?

Answer 23

Values decrease due to increasing atomic radius and the screening effect of inner electrons.

Question 24

Why is the first ionisation energy of xenon less than that of neon?

Answer 24

Xenon has a larger atomic radius.

Question 25

Give properties of a transition metal?

Answer 25

Variable valency, good catalysts, formation of coloured compounds, and d-orbitals.

Question 26

Define electronegativity?

Answer 26

Measure of attraction that an atom in a molecule has for a shared pair of electrons.

Question 27

How is an ionic bond formed between a pair of atoms?

Answer 27

One atom gains electrons and the other loses electrons, creating attraction between oppositely charged ions. Electronegativity difference is >1.7.

Question 28

Define a (pure) covalent bond?

Answer 28

The sharing of electrons where electronegativity difference is 0.

Question 29

Define a polar covalent bond?

Answer 29

Unequal sharing of electrons where electronegativity difference is <1.7.

Question 30

How is a double covalent bond between pairs of atoms?

Answer 30

It is the sharing of two pairs of electrons.

Question 31

Describe the bonding in a metallic crystal.

Answer 31

Positive ions with free-moving electrons.