structure and bonding

what is ionic bonding?

the transfer of electrons from a metal atom to a non metal atom

what does ionic bonding form?

positively charged metal ions and negatively charged non-metal ions

describe what happens when a magnesium atom reacts with an oxygen atom to form magnesium oxide

magnesium loses 2 electrons to form a Mg²⁺ ion. oxygen gains these 2 electrons to form an O²⁻ ion. the electrons are transferred from magnesium to oxygen, forming ionic bonds between the magnesium ions and oxide ions

what are the properties of ionic compounds?

high melting and boiling points, conduct electricity when molten or dissolved in water, usually soluble in water

what force holds ions together in an ionic bond?

electrostatic attraction between positive and negative ions

why do ionic compounds have high melting and boiling points?

the strong electrostatic forces between ions need a lot of energy to break

why can ionic compounds conduct electricity when dissolved in water or molten?

the ions are free to move and carry a charge

are ionic compounds usually brittle or flexible and why?

brittle because when layers of ions shift, similar charges repel each other, causing the compound to break

what is covalent bonding?

two non-metal atoms share pairs of electrons to achieve full outer electron shells

what is a double covalent bond?

when two atoms share two pairs of electrons, like in oxygen

what are the properties of simple molecules?

low melting and boiling points, don’t conduct electricity, often gases or liquids

why do simple molecules have low melting and boiling points and are often liquids/gases at room temperature?

they have weak intermolecular forces that don’t require much energy to break

can simple molecular substances conduct electricity?

no because they don’t have charged particles (ions or free electrons) that can move and carry a current

describe the structure and bonding of giant covalent structures

diamond and graphite have a continuous network of covalently bonded atoms

is graphite soft or hard and why?

soft because the carbon atoms are arranged in layers held together by weak forces that can easily slide over each other

why do giant covalent structures like diamond have high melting points?

every atom is bonded to many others with strong covalent bonds, which need a lot of energy to break

why can graphite conduct electricity but diamond can’t?

in graphite, each carbon atom is bonded to three others, leaving a delocalised electron that slides through the layers with a charge and conducts electricity. in diamond, all four electrons are involved in bonds

what are some examples are giant covalent structures?

diamond, graphite, silicon dioxide (sand)

what are fullerenes?

molecules of carbon atoms arranged in hollow spheres, tubes or ellipses

what is the shape of a buckyball fullerene?

it’s shaped like a hollow sphere

what is a potential use of carbon nanotubes?

they can be used in electronics, nanomedicine, or strong lightweight materials

why are fullerenes used as lubricants?

the spherical or tube-like shapes can roll easily, reducing friction

what is metallic bonding?

occurs between metal atoms, where delocalised electrons move freely through a lattice of positive ions

how do the delocalised electrons affect the properties of metals?

they allow metals to conduct electricity and heat and make them malleable

why are the metals malleable?

the layers of metal ions can slide over each other without breaking the metallic bond

what is an alloy?

a mixture of metal with one or more other elements

give an example of an alloy

steel is an alloy of iron and carbon

how are alloys different from pure metals?

alloys are a mixture of metals, making them harder and less malleable than pure metals

why are alloys used instead of pure metals?

they’re often stronger, harder and more resistant to corrosion

what is nanotechnology?

working with materials that are small, like atoms

how small are nanomaterials?

between 1 and 100 nanometres in size

what’s one benefit of using nanoparticles in medicine?

they can deliver drugs directly to specific cells, improving treatment effectiveness

why do nanometres often have different properties compared to the same material at a larger scale?

their large surface area compared to volume changes how they interact with other substances

give one advantage of using nanoparticles in suncream

they provide better protection from the sun’s harmful UV rays because they cover the skin more evenly

give one disadvantage of using nanoparticles in sun cream

the long term effects of nanoparticles on human health and the environment aren’t fully understood