aqa a level chemistry periodicity and group 3 elements

how are elements arranged in the periodic table

by increasing atomic number

define ionisation energy

it is the minimum amount of energy required to remove 1 mole of electrons from 1 mole of atoms in the gaseous state

which element is classified as a d block element- antimony, molybdenum, strontium, uranium

molybdenum

which ion has the largest radius- F-, MG2+, NA+, O2-

O2-

which element has a first ionisation energy lower than of sulfur- chlorine, oxygen, phosphorus, selenium

selenium

give an equation including state symbols for the reaction of sodium with water, suggest why it is dangerous to react a similar piece of sodium with 10cm3 of water in a boiling tube

2Na (S) + 2H2O (l)= 2NaOH (Aq) +H2(G)

the temperature will go up more

give an equation for the reaction of phosphorus oxide with water

suggest a ph for the solution formed

P4O10 + 6H2O=4H3PO4

+1

Explain, in terms of crystal structure and bonding, why silicon(IV) oxide has a higher melting point than phosphorus(V) oxide.

SiO2 is macromolecular structure -giant covalent

with many Strong covalent bonds (between atoms.

therefore a lot of energy is required to break and overcome the strong covalent bonds

P4O10 is a simple covalent molecule with Weak van der Waals forces between molecules

therefore less energy is required to break and overcome the weak van der waals forces

An element in Period 3 forms an oxide that is insoluble in water.

This oxide reacts with sulfuric acid and with aqueous potassium hydroxide. Give the formula for this oxide.

Give an equation for the reaction of this oxide with sulfuric acid.

Al2O3

Al2O3 + 3 H2SO4 → Al2(SO4)3 + 3 H2O

Give the formula of a hydroxide of an element in Period 3 used in medicine.

Mg(OH)2

There is a general trend for an increase in ionisation energy across Period 3.

Give one example of an element that deviates from this trend.

Explain why this deviation occurs.

Aluminium

the Outer electron is in the 3p orbital

so is slightly more shielded (than 3s)

The graph shows the successive ionisation energies of a Period 3 element, X.

Identify element X. Explain your choice.

M1 Phosphorus

M2 large jump in ionisation energy for the 6th ionisation energy

M3 This is when the electron is being removed from the 2nd energy level

Which represents the correct order of increasing radius of the ions?

A F- O2- Li+ Be2+

B Li+ Be2+ O2- F-

C Be2+ Li+ F- O2-

D O2- F- Li+ Be2+

C

Identify the element in Period 3, from sodium to argon, that has the highest second ionisation energy.

Give an equation, including state symbols, to show the process that occurs when the second ionisation energy of this element is measured.

M1 Na 1

M2 Na+ (g) → Na2+(g) + e-

Explain why the atomic radius decreases across Period 3, from sodium to chlorine.

The number of protons increases

Therefore, the attraction between the nucleus and electrons increases

also Shielding is similar

Phosphorus burns in air to form phosphorus(V) oxide. Give an equation for this reaction.

4P + 5O2 → P4O10 OR P4 + 5O2 → P4O10

State the meaning of the term periodicity

Repeating pattern and trends (of physical and chemical properties

Identify the element in Period 4 with the highest electronegativity value.

Bromine

Identify the element in Period 4 with the largest atomic radius

Explain your answer

Potassium

The smallest number of protons and smallest nuclear charge

Also Similar shielding

Name the property of arsenic(III) oxide that describes its ability to react in these two ways.

Amphoteric

Which element has the highest first ionisation energy?

A Aluminium

B Phosphorus

C Silicon

D Sulfur

B

Which is the correct order of melting points of these Period 3 elements?

A phosphorus > sulfur > chlorine > argon

B argon > chlorine > phosphorus > sulfur

C sulfur > phosphorus > chlorine > argon

D chlorine > phosphorus > sulfur > argon

C

Which elements are shown in increasing order of the stated property?

A Atomic radius: phosphorus, sulfur, chlorine.

B First ionisation energy: sodium, magnesium, aluminium

C Electronegativity: sulfur, phosphorus, silicon.

D Melting point: argon, chlorine, sulfur.

D

Which of these elements has the highest second ionisation energy?

A Na

B Mg

C Ne

D Ar

A

Explain why the melting point of sulfur (S8) is greater than that of phosphorus (P4)

S8 molecules are bigger than P4 molecules

Therefore, van der Waals between molecules are stronger in sulfur

Explain why sodium oxide forms an alkaline solution when it reacts with water.

Sodium oxide contains O2- ions

These O2- ions react with water forming OH- ions

Write an ionic equation for the reaction of phosphorus(V) oxide with an excess of sodium hydroxide solution

P4O10 + 12OH- 4PO4 3- + 6H2O

State what is used to ionise a sample of indium in a mass spectrometer.

Using an electron gun to beam loads of electrons

State why more than the minimum energy is not used to ionise the sample of indium.

So no more than 1 electron is knocked out

Give two reasons why the sample of indium must be ionised.

accelerate

deflect

There is a similar general trend in first ionisation energies for the Period 4 elements gallium to krypton.

State how selenium deviates from this general trend and explain your answer

Lowers

Paired electrons in a (4) p orbital

(Paired electrons) repel

Suggest why the first ionisation energy of krypton is lower than the first ionisation energy of argon.

Kr is a bigger atom with more shells

Identify the Period 2 element, from carbon to fluorine, that has the largest atomic

radius. Explain your answer.

carbon

fewer protons therefore smaller nuclear charge

similar shielding

State the general trend in first ionisation energies from carbon to neon. Deduce the element that deviates from this trend and explain why this element deviates from the trend.

increases

oxygen

Paired electrons in a (2)p orbital

paired electrons in the p orbital repel each other

Explain why the second ionisation energy of carbon is higher than the first ionisation energy of carbon.

more energy is required to remove an electron from a more positive ion

Deduce the element in Period 2, from lithium to neon, that has the highest second ionisation energy.

lithium

Explain, in terms of its structure and bonding, why nickel has a high melting point.

Strong metallic bond

Strong electrostatic forces of attraction between positive (metal) ions and delocalised electrons

Explain why nickel is ductile

all of the cations are the same size so the layers of atoms can slide over each other and be separated

Describe the bonding in metals.

lattice of positive metal ions surrounded by a sea of delocalised electrons

Explain why the melting point of magnesium is higher than that of sodium.

greater ionic charge

smaller atoms

more delocalized electrons

stronger attraction between positivley charged ions and delocalised electrons

explain how metals conduct electricity

delocalized electrons flow in a given direction

The Ne atom and the Mg2+ ion have the same number of electrons. Give two reasons why the first ionisation energy of neon is lower than the third ionisation energy of magnesium

Mg2+ ion smaller than Ne atom

Mg2+ has more protons than Ne

Explain why the first ionisation energy of sulphur is lower than would be predicted from the general trend.

electrons pair in the 3p sub level

repulsion between electrons in this pair

The elements phosphorus, sulfur, chlorine and argon are in the p block of the Periodic Table. State why these elements are classified as p block elements.

outer electrons are in the p orbital

In terms of atomic structure, explain why the van der Waals' forces in liquid argon are very weak.

Argon particles are single atoms with electrons closer to nucleus

Cannot easily be polarised