3.1

Question 1

Physical properties of group 2 elements

Answer 1

•high melting points and boiling points
•light metals with low densities
•form colourless (white) compounds

Question 2

Why does reactivity increase as you go down the group2?

Answer 2

•down a group, shielding increases
•The outer electrons experience less attraction towards the nucleus
•This causes a decrease in the first and second ionisation energies

Question 3

What happens when a group 2 element reacts with oxygen ?

Answer 3

Burns with a bright flame and it produces a metal oxide forming a white power

Question 4

What kind of reaction is it when a group two element reacts with oxygen ?

Answer 4

Redox reactin

Question 5

What happens when group two elements react with water?

Answer 5

They undergo a redox reaction, and form aqueous metal hydroxides, becomes more vigorous as we go down the group

Question 6

Magnesium reaction with cold water and steam

Answer 6

•Reacts lightly with liquid cold water to form magnesium hydroxide and hydrogen
•Reacts vigorously with steam to form magnesium oxide and hydrogen

Question 7

What happens when group 2 elements react with dilute hydrochloric acid ?

Answer 7

Form a soluble salt and hydrogen gas

M(s) + Acid (aq) —> Salt(aq) + H*2(g)

Question 8

What do groups have in common?

Answer 8

Same number of electrons in outer shell

Question 9

What does the period number tell us?

Answer 9

The number of the highest energy electron shell for the elements of that period

Question 10

What is periodicity?

Answer 10

Trend in properties that is repeated across each period

Question 11

How does atomic radius vary across a period?

Answer 11

Decreases
•as you move across a period each element has more protons in its nucleus, increasing the positive charge means that, increased attraction between the nucleus and the electrons, drawing them closer
•shielding is the same

Question 12

How does atomic radius vary down a group?

Answer 12

Increases
•more shells so the outer electron shell is further from the nucleus
•increases shielding between the nucleus and the outer electron
—->less attraction between the outer electron and nucleus

Question 13

What is the first ionisation energy?

Answer 13

The first ionisation energy is the energy needed to remove one mole of electrons from one mole of atoms in their gaseous state to form one mole of 1+ ions (also in their gaseous state)

Question 14

Example of first ionisation energy for Mg

Answer 14

Mg (g) —-> Mg+(g) + e-

Question 15

How does first ionisation energy vary across a period?

Answer 15

Decreases
•more protons, increases attraction between nucleus and electrons
Both the increased nuclear charge and the decreased atomic radius mean that outer electrons are more attracted to the nucleus
•same shielding

Question 16

How does first ionisation energy vary down a group?

Answer 16

Decreases
•atomic radius increases si outer electron shell is further away from nucleus
•more shielding between nucleus and outer electrons, attraction between nucleus and outer electrons decreases
•

Question 17

What are key features of the giant metallic lattice structure? /features of metals

Answer 17

•cations are fixed in place and cannot move
•delocalised electrons are free to move- so they are good conductors of electricity
•delocalised electrons they a strong electrostatic attraction to cations -high melting and boiling points
•dont dissolve

Question 18

What do metals with 2+ cations have?

Answer 18

2x electrons

Question 19

Giant covalent lattice

Answer 19

Many billions of atoms held together by a network of strong covalent bonds (boron carbon silicon)
•

Question 20

Properties of giant covalent structures

Answer 20

•High mpt/bpt (covalent bonds strong so high energy to break)
•insoluble in almost all solvents (bonds r too strong to be broken by interactions w solvents)
•diamond silicon cant conduct elec- no delocalised electrons, graphene and graphite can conduct

Question 21

Graphene

Answer 21

Single layer of graphite, hexagonally arranged planar (120*) carbons
-conducts
-thin and strong

Question 22

Graphite

Answer 22

•parallel layers hexagonally arranged carbon atoms (planar 120*)
Layers bonded by weak london forces, spare delocolised electrons between layers, conducts

Question 23

What are group 2 elements referred to?

Answer 23

Alkaline earth metals

Question 24

How do group 2 elements act as reducing agents?

Answer 24

By transferring their two electrons , in their s sub shells of their outer shell are lost when they react

Question 25

Reactions between group 2 oxides and water

Answer 25

MO(s) +H2 O(l)—> M(OH)2(aq)

Question 26

What happens to the solubility of group 2 as you go down the group?

Answer 26

Increases down the group, when a hydroxide is more soluble than another it releases more OH- ions and so make a more alkaline solution with a higher pH
-Beryllium oxide is insoluble in water

Question 27

What are uses of group 2 compounds?

Answer 27

-Neutralising acidic soils
Calcium hydroxide, Ca(OH)2 is used by farmers to reduce the acidity levels of soil
-indigestion remedies
Magnesium hydroxide can be used to neutralise excess acid producing salt and water.
-building and construction uses
Calcium carbonate (CaCO3) used as building material

Question 28

What are the halogens?

Answer 28

-group 7
-7 outer shell electrons, 5 being in the p sub-shell
-strong oxidising agents

Question 29

how does reactivity vary as you go down group 7?

Answer 29

Reactivity decreases
-the atomic radius increases (the nuclear pull is further away from the incoming electrons)
-shielding increases
-the ability to gain an electron in the p sub shell and form 1- ions decreases

Question 30

What are the appearances and state of the halogens at RTP

Answer 30

F2
-pale yellow gas (reacts w/ almost any substance)
Cl2
- pale green gas
Br2
-red-brown liquid
I2
-shiny grey-black solid
At2
never been seen (radioactive + decays rapidly)

Question 31

trend in boiling points down the halogens?

Answer 31

Increases
-more electrons, stronger London forces, –>more energy to break
intermolecular forces

Question 32

What are the Halogen-halide displacement reactions?

Answer 32

○ Cl2 reacts with Br-
(Cl2(aq) + 2Br-(aq) →2Cl-(aq) + Br2(aq) orange)
○ Cl2 reacts with I-
(Cl2(aq) + 2I-(aq) → 2Cl-(aq) + I2(aq) violet)
○ Br2
reacts with I-
only (Br2 (aq) + 2I-(aq) → 2Br- (aq)+ I2 (aq) violet)
○ I2 doesn’t react at all

Question 33

colour in water for the halogens? and colour in cyclohexanes?

Answer 33

solution in water
Cl=pale green, Br=orange, I=brown
Solution in cyclohexane (/nonpolar solvent) top layer: Cl=pale green, Br=orange,
I=violet

Question 34

What is disproportionation?

Answer 34

a reaction in which the same element is both reduced and oxidised e.g reaction of chlorine with water (used in water purification)

Question 35

What are benefits and risks of having chlorine in water?

Answer 35

kills bacteria preventing disease e.g.cholera. Risks: can react
with organic hydrocarbons (formed by decaying vegetation) to make chlorinated
hydrocarbons

Question 36

disproportionation of chlorine with water

Answer 36

e.g. Cl2
(aq) + H2O (l) → HClO (aq) + HCl (aq) (bacteria killed by chloric (I)
acid/ions, chloric (I) acid acts as weak bleach- indicator paper will turn red then
white)
○ Cl2
(aq) + 2NaOH (aq)→ NaCl (aq) + H2O (l) + NaClO (household bleach)

Question 37

How does electronegativity vary across a period?

Answer 37

increases