Periodicity

Question 1

What does the group number indicate

Answer 1

The number of valency electrons

Question 2

What does the period number indicate

Answer 2

The number of electron shells

Question 3

What group is alkali metals

Answer 3

group 1

Question 4

What group is halogens

Answer 4

group 17

Question 5

Define periodicity

Answer 5

The repeating pattern of physical and chemical properties shown by the different periods

Question 6

Define Atomic radius

Answer 6

The distance between the nucleus and most outer electron

Question 7

How is atomic radius calculated

Answer 7

As the position of the outer most electron is impossible to be known precisely it is taken as half the distance between the nuclei of two bonded atoms of the same element

Question 8

How does atomic radius change across a group and period and why

Answer 8

Atomic radius increases down a group as additional electron shells are present and atomic radius decreases across a period as the charge between nucleus and electrons increases as the proton number increases

Question 9

Define ionic radius

Answer 9

The distance between the nucleus and most outer electron of an ion

Question 10

How does ionic radius change for Cations

Answer 10

Ionic radius decreases as the atoms loses an entire energy level when ionizing

The radius increases down a group as there are more electron shells

The radius decreases across the group as the valency electron number remains the same but the proton number increases and the attraction is stronger

Question 11

How does ionic radius change for anions across a period and group.

Answer 11

The radius increases down a group as there are more electron shells

The radius decreases across the group as the electron number remains the same but the electron number decreases and the attraction is stronger

Question 12

How do melting points change down group 1 and 17. Explain why.

Answer 12

Melting points decrease down group 1 as metalic bonding strength decreases down the group as the ionic radius increases

Melting points increase down group 17 as intermolecular forces increase due to the repulsion of nuclei decreasing given increased ionic radius

Question 13

How do first ionisation energy change down the group and across a period?

Answer 13

Values decrease down a group a the valency electron is further away from the positive nucleus

The values increase across a period as additional electrons are added to the electron shell increasing the attraction to the nucleus. Additionally if electrons are of opposite spin the ie will be lower as their will be repulsion between electrons

Question 14

Define electronegativity

Answer 14

A relative measure of attraction between an atom and a shared pair of electrons when it is covalently bonded

Question 15

How does electronegativity change across a period and down a group. Explain why

Answer 15

As the size of the atom increases the electronegativity decreases thus electronegativity decreases down a group and increase across a period

Question 16

Define electron affinity

Answer 16

The energy change measured when one mole of electrons are added to an isolated atom in its gaseous states

Question 17

Explain first and second electron affinity for oxygen

Answer 17

The first electron added has a negative vale for oxygen as the electron wants to gain another electron but adding a second electron requires energy as the atom is negatively charged and the repulsion must be overcome.

Question 18

How does reactivity change in group 1 and why?

Answer 18

The reactivity increases down the group as the distance between nucleus and valency electron increases and thus attraction decreases allowing the electron to be lost easier

Question 19

How does reactivity change down group 17 and why?

Answer 19

The reactivity decreases down the group as the distance between nucleus and valency shell increases and thus attraction decreases between nucleus and free electrons

Question 20

Test for halide ions

Answer 20

The pressence of a halogen in a solution cam be detected by adding silver which will form a precipitate

Question 21

Color of

Silver chloride
Silver Bromide
Silver Iodide

Answer 21

Silver chloride - white
Silver Bromide - cream
Silver Iodide - yellow

Question 22

Define transition metal

Answer 22

An element that possess an incomplete d sub level in one or more of its oxidation states

Question 23

Why isn’t Zinc a transition metal

Answer 23

Zn can from only two ions, Zn+1, and Zn+2 which all have a full d sub level

Question 24

Properties of transition elements

Answer 24

-Catalytic properties
-Forms ligands
-Variable oxidation states
-Forms coloured compounds
-Magnetic properties

Question 25

4 examples of catalysts

Answer 25

Iron in harbor process [Nitrogen + hydrogen –> ammonia] reversible
Vanidium (V) oxide in the contact process [sulfur dioxide + oxygen –> sulfur trioxide] reversible
Nickle in hydrogentaion reactions [ethene + hydrogen –> ethane]
Manganese (IV) with hydrogen peroxide [hydrogen peroxide –> water + oxygen]

Question 26

Explain ferro-magnetism and provide three examples

Answer 26

This is when unpaired electrons (domains) align parrallel to each other regardless wether an external magnetic field is present.

Fe, Co, Ni

Question 27

Explain paramagnetism

Answer 27

Electrons which are unpaired do not cancel out their spins. These spins will create a small magnetic field, and will line up in an electrical or magnetic field. The more unpaired electrons the more paramagnetic the complex will be.

Question 28

Explain diamagnetism

Answer 28

When all the electrons in a transition metal complex are paired up the complex is said to be diamagnetic

Question 29

What dictated wether a ligand complex with iron will be paramagnetic or diamagnetic?

Answer 29

If the ligand is low in the spectrochemical series it will split the 5 d oriibital only slightly allowing for electrons to occupy the split sub level producing paramagentism

If the ligand is high in the spectrochemical series it will split the 5 d oriibital only a lot, not allowing for electrons to occupy the split sub level producing diamagnetism as all electrons are paired

Question 29

Define lignand

Answer 29

Ligands are neutral molecules or anions which contain a non-bonding pair of electrons.

Question 30

How do complex ions form

Answer 30

Ligands are neutral molecules or anions which contain a non-bonding pair of electrons These electron pairs can form co-ordinate covalent bonds with the metal ion to form complex ions.

Question 31

What factors affect the color of transition metal complexes?

Answer 31

• The nature of the transition element
  -Oxidation state of transition metal
  -The identity of the ligand
  -The shape of the molecule or ion
  -How much the d orbitals split

Question 32

What is a coordination number in complex ions?

Answer 32

The number of lone pairs bonded to the metal ion in a complex ion.

Ex. [ Fe (CN)6 ] 3-
coordination number is 6

Question 33

How does splitting of D orbitals occur and how does color come as a result?

Answer 33

All d orbitals are of equal energy. The d orbitals which lie ALONG the x-y and z axis are repelled by ligands causing the orbitals to split. Those (two) which lie along the axis go to a higher level and the remaining three go to a lower energy level.

Electrons are promoted by absorbing wavelength, and if they are promoted for example by red light, the color they will show is blue light as it is complementary.

Question 34

What factors affect d orbital splitting in complex ions?

Answer 34

• The transition metal as the number of protons in the nucleus change
• Oxidation state of the metal as the number of electrons in the level will change
• The electron density of the ligand

Question 35

How do complementary colors work?

Answer 35

If a white light is passed through a solution where the wavelength corresponding to the color red is absorbed than the observer will see the color which corresponds to the opposite wavelength of on the color wheel to red

Question 36

What type of bonding is present in Silicon and Diamond

Answer 36

macromolecular covalent structure with very strong bonds resulting in very high melting point.

Question 37

Why does Helium have a higher first ionisation energy than hydrogen even though the electron being removed has opposite spin repulsion?

Answer 37

Helium is a noble gas with a stable configuration

Question 38

Why does Beryllium have a higher first ionisation energy than Lithium even though the electron being removed has opposite spin repulsion?

Answer 38

Beryllium has its electron removed from its fully filled 2S orbital, which is more stable than lithium’s partialy filled 2S orbital

Question 39

How do we know which of two elements both showing paramagnetism will have a stronger magnetic field?

Answer 39

The more unpaired electrons there are in the complex the more paramagnetic the complex will be.

Question 40

Why is zinc not considered a transition element?

Answer 40

Zn is not considered to be a transition element as it does not form ions with incomplete d-orbitals and all of its compunds are colorless

Question 41

Why do different transition metals have different ligand colored complexes?

Answer 41

The amount that the d orbitals are split will determine the exact colour. Changing the transition metal changes the number of protons in the nucleus which will affect the levels.

Question 42

Do anions have a larger or smaller radius than their atom and why?

Answer 42

Anions have a larger radius than there atoms as the number of electron-electron repulsion interactions that take place