the periodic table

Question 1

What is the arrangement of elements in the periodic table based on?

Answer 1

Increasing atomic number

Elements are placed in vertical columns (groups) and horizontal rows (periods)

Question 2

What is periodicity?

Answer 2

Repeating patterns in chemical and physical properties across periods

Question 3

Define atomic radius.

Answer 3

Distance between the nucleus and the outermost electron of an atom

Question 4

How is atomic radius measured?

Answer 4

By measuring the distance between the nuclei of two atoms of the same element and halving this distance

Question 5

What is the atomic radius of sodium (Na)?

Answer 5

0.157 nm

Question 6

What is the trend in atomic radii across Period 3 elements?

Answer 6

Decreases across the period

Question 7

Why does atomic radius decrease across Period 3?

Answer 7

Increasing nuclear charge pulls electrons closer to the nucleus

Question 8

Define ionic radius.

Answer 8

Distance between the nucleus and the outermost electron of an ion

Question 9

How do cations compare in size to their parent atoms?

Answer 9

Cations are smaller than their parent atoms

Question 10

What happens to the ionic radius of anions compared to their parent atoms?

Answer 10

Anions are larger than their parent atoms

Question 11

What is the ionic radius of Na+?

Answer 11

0.095 nm

Question 12

What trend is observed in melting points across Period 3?

Answer 12

General increase from Na to Si, followed by a sharp drop from P to Ar

Question 13

Which Period 3 element has the highest melting point?

Answer 13

Silicon (Si) at 1683 K

Question 14

What is electrical conductivity?

Answer 14

How well a substance can conduct electricity

Question 15

What trend is observed in electrical conductivity across Period 3?

Answer 15

Initial increase from Na to Al, followed by a decrease across remaining elements

Question 16

What is the electrical conductivity of silicon (Si)?

Answer 16

2 x 10^-10 S m^-1

Question 17

What bonding type do Na, Mg, and Al exhibit?

Answer 17

Metallic bonding

Question 18

Describe the structure of metallic elements in Period 3.

Answer 18

Giant metallic lattice held together by a ‘sea’ of delocalised electrons

Question 19

What type of structure do non-metallic elements in Period 3 have?

Answer 19

Simple molecular structure

Question 20

What is the melting point of phosphorus (P)?

Answer 20

317 K

Question 21

What reaction occurs when sodium reacts with water?

Answer 21

2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g)

Question 22

What is formed when magnesium reacts with water?

Answer 22

Mg(OH)2 (aq) + H2 (g)

Question 23

What is the oxidation number of sodium in Na2O?

Answer 23

+1

Question 24

What is the oxidation number of aluminum in Al2O3?

Answer 24

+3

Question 25

What is the oxidation state of phosphorus in P4O10?

Answer 25

+5

Question 26

What is the electronegativity trend among Period 3 elements?

Answer 26

Chlorine and oxygen are more electronegative than other Period 3 elements

Question 27

What happens to the ionic radii from Na+ to Si4+ across Period 3?

Answer 27

Ionic radii decrease due to increasing nuclear charge

Question 28

What is the melting point of argon (Ar)?

Answer 28

84 K

Question 29

Fill in the blank: The ionic radius of Mg2+ is _______.

Answer 29

0.065 nm

Question 30

What is the oxidation number of a single Na atom in Na2O?

Answer 30

+1

Question 31

What is the oxidation number of a single Al atom in Al2O3?

Answer 31

+3

Question 32

What is the oxidation number of a single P atom in P4O10?

Answer 32

+5

Question 33

How many O atoms are in Al2O3 and what is their total oxidation contribution?

Answer 33

3 O atoms contribute -6

Question 34

What is the oxidation state of Mg in MgCl2?

Answer 34

+2

Question 35

What is the oxidation state of Cl in MgCl2?

Answer 35

-1

Question 36

Which Period 3 oxides do not react with water?

Answer 36

Al2O3, SiO2

Question 37

What is the pH of the solution formed when Na2O reacts with water?

Answer 37

12 - 14 (Strongly alkaline)

Question 38

What type of bonding is present in Na2O?

Answer 38

Ionic

Question 39

What is the acid/base nature of Al2O3?

Answer 39

Amphoteric

Question 40

What happens when P4O10 reacts with water?

Answer 40

Forms H3PO4 (aq)

Question 41

What is the primary use of Mg(OH)2?

Answer 41

Used in indigestion remedies

Question 42

What is the reaction of Na2O with HCl?

Answer 42

Na2O (s) + 2HCl (aq) → 2NaCl (aq) + H2O (l)

Question 43

Fill in the blank: The electronegativity of Cl is _______.

Answer 43

3.0

Question 44

What type of structure does SiO2 have?

Answer 44

Giant covalent

Question 45

What occurs when SiCl4 is hydrolyzed in water?

Answer 45

Releases HCl gas and forms SiO2 precipitate

Question 46

What is the bonding type in MgCl2?

Answer 46

Ionic

Question 47

What happens to the oxidation number of Al when it reacts with water?

Answer 47

It can act as both an acid and base

Question 48

What is the characteristic behavior of chlorides of Period 3 elements when added to water?

Answer 48

They form solutions that can be acidic or neutral

Question 49

True or False: The oxides of Na and Mg produce acidic solutions with water.

Answer 49

False

Question 50

What is the chemical equation for SO2 reacting with water?

Answer 50

SO2 (s) + H2O (l) ⇌ H2SO3 (aq)

Question 51

What is the electronegativity trend across Period 3?

Answer 51

Increases from Na to Cl

Question 52

What is the structure of NaCl?

Answer 52

Giant ionic

Question 53

What is the oxidation number of P in PCl5?

Answer 53

+5

Question 54

What type of oxide is Al2O3?

Answer 54

Amphoteric

Question 55

What is the reaction of Al2O3 with H2SO4?

Answer 55

Forms Al2(SO4)3 + H2O

Question 56

What reaction occurs when NaOH reacts with HCl?

Answer 56

Forms NaCl + H2O

Question 57

What is a giant metallic lattice?

Answer 57

A giant metallic lattice is a structure formed by metal cations held together by delocalised electrons that can freely move around. ## Footnote This structure contributes to the metallic properties of elements like sodium, magnesium, and aluminium.

Question 58

Why is aluminium a better electrical conductor than sodium and magnesium?

Answer 58

Aluminium has a stronger metallic bonding due to more delocalised electrons, leading to better electrical conductivity. ## Footnote The electrostatic forces between a 3+ ion and a larger number of delocalised electrons are much stronger than those in sodium.

Question 59

What is the structure of silicon?

Answer 59

Silicon has a giant molecular structure where each silicon atom is held to its neighbours by strong covalent bonds. ## Footnote This structure lacks delocalised electrons, which is why silicon cannot conduct electricity.

Question 60

List the non-metallic elements mentioned in the text.

Answer 60

* Phosphorous * Sulfur * Chlorine * Argon ## Footnote These elements exist in different molecular structures.

Question 61

What type of forces exist between molecules of phosphorous, sulfur, and chlorine?

Answer 61

Weak instantaneous dipole-induced dipole forces. ## Footnote These forces require little energy to break, explaining the low melting points of these non-metals.

Question 62

What is the bonding type of sodium, magnesium, and aluminium?

Answer 62

Metallic bonding. ## Footnote These elements form giant metallic structures with positive ions arranged in a lattice.

Question 63

What is the structure of the chlorides of Period 3 elements?

Answer 63

* NaCl: Giant ionic * MgCl2: Giant ionic * Al2Cl6: Simple molecular * SiCl4: Simple molecular * PCl5: Simple molecular * SCl2: Simple molecular ## Footnote The structure shifts from giant ionic to simple molecular across the group.

Question 64

How does the melting point trend across Period 3 elements?

Answer 64

Melting points increase from sodium to aluminium and then decrease from phosphorous to argon. ## Footnote This is influenced by the type of bonding and structure.

Question 65

What type of bonding is present in the oxides of Period 3 elements?

Answer 65

* Na2O: Ionic * MgO: Ionic * Al2O3: Ionic (with some covalent character) * SiO2: Giant covalent * P4O10: Simple molecular * SO2: Simple molecular * SO3: Simple molecular ## Footnote This shows a transition from ionic to covalent bonding.

Question 66

True or False: The electrical conductivity of Period 3 elements decreases due to a lack of delocalised electrons.

Answer 66

True. ## Footnote This lack of delocalised electrons affects their ability to conduct electricity.

Question 67

Fill in the blank: The presence of a _______ of delocalised electrons determines whether an element is a good conductor.

Answer 67

[sea] ## Footnote The 'sea' of delocalised electrons is crucial for electrical conductivity in metals.

Question 68

What is the significance of an element's position in the Periodic Table?

Answer 68

It allows predictions about the element's chemical and physical properties. ## Footnote Understanding an element's position helps deduce its behavior in reactions.

Question 69

How can the position of an unknown element be deduced?

Answer 69

By analyzing its chloride and oxide properties, such as pH and melting point. ## Footnote Systematic breakdown of the properties can lead to identifying the element's group and period.

Question 70

What type of reaction occurs when Group 15 chlorides react with water?

Answer 70

Hydrolysis reaction. ## Footnote This leads to the formation of acidic solutions.

Question 71

What white fumes are produced when the chloride of Group 15 element Y reacts with water?

Answer 71

Hydrogen chloride gas. ## Footnote This is typical for reactions of Group 15 chlorides with water.