Use a copy of the Periodic Table where you need one.
Oxygen reacts with a metal X to form an ionic compound XO. Which statement about oxygen is correct when forming this compound?
Source: 2023 GESS Sec 3 End-of-Year P1 Q10
Which of the following elements would be expected to form the largest ion (most number of electron shells) with a noble gas configuration?
Source: 2023 XMS Sec 3 WA2 Q1
Element P has an electronic configuration of 2.8.8.2. Element Q has an electronic configuration of 2.8.7. What is the likely chemical formula of the compound containing only P and Q?
Source: 2023 XMS Sec 3 WA2 Q2
Which particles enable the conduction of electricity through metals?
Source: 2023 XMS Sec 3 WA2 Q4
Iron is a metal. Its structure consists of a giant lattice of positive ions in a ‘sea of electrons’. Which statements about solid iron are correct?
1 Iron conducts electricity because the electrons are free to move.
2 Iron conducts heat because the positive metal ions are free to move.
3 Iron has a high melting point due to the strong ionic bonds.
4 Iron is malleable because the layers of atoms can slide over one another.
Source: 2023 PLMGS Sec 3 End-of-Year P1 Q6
The diagram shows the structure of brass.
Why is brass harder than pure copper?
Source: 2024 Dunman Sec 4 Prelim P1 Q29
Carbon has many allotropes, including diamond, buckyball, graphite and single-walled carbon nanotubes (SWCNT). Carbon atoms have four valence electrons and prefer to share electrons rather than transfer them. A buckyball is a molecule made of 60 carbon atoms. SWCNT is one flat sheet of carbon atoms rolled into a cylinder, and graphite is a stack of such sheets. Each carbon atom in buckyball, SWCNT and graphite is bonded to three other carbon atoms, so these structures have one delocalised electron per carbon atom. Each carbon atom in diamond is bonded to four other atoms. The table shows some properties.
| property | diamond | buckyball | graphite | SWCNT |
|---|---|---|---|---|
| electrical conductivity / S per cm | 0.001 | 0.00001 | 4000 | 1 000 000 |
| relative electron movement speed | low | very low | high | very high |
| melting point / °C | 4030 | 600 | 3600 | 3550 |
| relative cost | high | very high | low | high |
| solubility in organic solvents | no | yes | no | no |
| flexibility | no | yes | no | yes |
Source: 2022 XMS Sec 3 WA2 B4, adapted
Carbon is a highly versatile element that exists in different forms such as diamond, graphite and fullerene. Figure 1 shows the structure of graphite and Figure 2 shows the structure of a buckyball, C60, which has 60 carbon atoms covalently bonded in a cage-like structure.
Figure 1 (left) and Figure 2 (right)
Source: 2023 XMS Sec 3 WA2 Q8
Oxygen and chlorine combine to form a brownish-yellow gas, dichlorine monoxide (Cl2O). Oxygen and chlorine also combine with aluminium to form aluminium oxide and aluminium chloride respectively.
| statement | true | false |
|---|---|---|
| (i) The ionic bonding in aluminium oxide is much stronger than in aluminium chloride. | ||
| (ii) Aluminium chloride has a simple molecular structure while aluminium oxide has a giant ionic lattice structure. | ||
| (iii) Both aluminium oxide and aluminium chloride can conduct electricity when molten. |
Source: 2024 SMSS Sec 3 End-of-Year P2 Q4
Sodium hydride, NaH, is an ionic compound formed between sodium and hydrogen.
Source: 2024 SMSS Sec 3 End-of-Year P2 Q5(a)
Ethanedioic acid, H2C2O4, is a colourless crystalline solid with a melting point of 103 °C. A student tested the electrical conductivity of the acid. The colourless crystals did not conduct electricity but the aqueous solution of the acid did.
Source: 2024 SMSS Sec 3 End-of-Year P2 Q6(a)
The SAE system gives each steel a four-digit designation. The first two digits show the type of steel and the last two digits show the percentage of carbon by weight. For example, 1060 is a plain carbon steel with 0.60 % carbon. Chromium steel is written 50XX.
| steel | carbon (%) | melting point / °C | use |
|---|---|---|---|
| low carbon | 0.05 to 0.30 | 1464 | car bodies |
| medium carbon | 0.30 to 0.60 | 1427 | machinery |
| high carbon | 0.60 to 1.00 | 1353 | bridge cables |
Source: 2024 SMSS Sec 3 End-of-Year P2 Q11, adapted
Flerovium, Fl, has atomic number 114. It has been suggested that flerovium is a typical metal.
Source: 2024 CHS Sec 3 End-of-Year Section B Q5(c)
Source: 2022 XMS Sec 3 WA2 B3(b)
Done atom of oxygen receives two electrons from an atom of X[1]
In XO, the ions are X2+ and O2−. Oxygen gains two electrons from the metal.
Cpotassium[1]
K+ is 2.8.8 with three shells. O2−, F− and Mg2+ are all 2.8, with two shells.
BPQ2[1]
P loses 2 electrons to form P2+. Q gains 1 electron to form Q−. Two Q− balance one P2+, so the formula is PQ2.
Delectrons only[1]
Only the delocalised electrons move. The positive ions stay in the lattice.
B1 and 4[1]
Only the electrons are mobile, so statement 2 is wrong. Iron has metallic bonding, not ionic bonding, so statement 3 is wrong.
BThe zinc atoms prevent layers of copper atoms from slipping over each other easily.[1]
Zinc atoms are a different size from copper atoms, so they disrupt the orderly layers. A larger force is then needed to make the layers slide.
Carbon has 4 valence electrons and prefers to share electrons rather than transfer electrons to form a bond. [1]
The higher the relative electron movement speed, the higher the electrical conductivity. [1]
Each carbon atom in SWCNT is bonded to three others. [1]
Each carbon atom in diamond is bonded to four others. [1]
So SWCNT has one delocalised electron per carbon atom that can conduct electricity, but diamond has none. [1]
Any two of the following: it is soluble in organic solvents, it has a low electrical conductivity of 0.00001 S per cm, it has a low melting point of 600 °C. [2]
C60 [1]
SWCNT (single-walled carbon nanotube). No mark is given for the name alone.
It has the highest electrical conductivity of all the carbon allotropes. [1]
It is also flexible. [1]
Any one: high melting point, insoluble in water (but soluble in organic solvent), conducts electricity, brittle or slippery. [1]
Comparison: both buckyball and graphite have each carbon atom covalently bonded to 3 other carbon atoms, with 1 unbonded electron that is delocalised, free-moving and mobile. [1]
Prediction: buckyball can conduct electricity. [1]
Correct shared electron pairs: the oxygen atom shares one pair with each chlorine atom, making two single bonds. [1]
Correct unshared electrons: oxygen has 2 lone pairs and each chlorine atom has 3 lone pairs, so every atom has an octet. [1]
(i) False [1]
(ii) True [1]
(iii) False [1]
Aluminium chloride has a low melting point, so it is made of simple molecules with no ions to carry current.
A sodium ion with the electronic arrangement 2.8 and a hydride ion with 2 electrons, all shown, each in square brackets. [1]
The correct charges, + on sodium and − on hydrogen, outside the brackets. [1]
Pure ethanedioic acid contains only molecules with no charge, so there are no mobile charged particles. [1]
In water, the acid forms mobile ions, which are charge carriers. [1]
5065 [1]
Low carbon steel has the highest malleability, so it can be easily moulded into the shapes of car bodies. [1]
High carbon steel has the highest tensile strength, so it can support the weight of the suspension bridge without breaking. [1]
High carbon steel [1]
It has more carbon atoms, which are a different size from iron atoms. [1]
They disrupt the orderly arrangement of the atoms more. [1]
A greater force is needed to slide the layers of atoms over one another. [1]
The idea of "more" must be present, or a maximum of 2 marks is given.
Flerovium has a giant metallic structure and oxygen has a simple molecular structure. [1]
Flerovium has a higher melting point than oxygen, because more energy is needed. [1]
This is to overcome the strong electrostatic forces of attraction between the positive metal ions and the sea of delocalised electrons in flerovium, compared with the weak intermolecular forces between the molecules in oxygen. [1]
The correct electrons: Ca2+ with no outer electrons shown and O2− with 8 outer electrons. [1]
The correct charges and ratio: one Ca2+ to one O2−, in square brackets. [1]