Predicting Chemical Reactions (OCR GCSE Combined Science A (Gateway): Chemistry): Flashcards

Reactivity decreases going down Group 7. Each successive element has more electron shells, so the outermost shell is further from the nucleus, making it harder for the atom to attract and gain an electron.

True.

Chlorine is more reactive than bromine because it has fewer electron shells, so its outer electrons are closer to the nucleus. This means chlorine can attract electrons more easily during a displacement reaction.

At room temperature, chlorine is a yellow-green gas, bromine is a red-brown liquid and iodine is a grey-black solid.

Halogen atoms form halide ions, which carry a -1 charge. This happens when a halogen atom gains one electron to complete its outer shell.

False.

Boiling points increase going down Group 7. Larger atoms have stronger intermolecular forces, so more energy is needed to overcome these forces and change state.

A metal halide salt is formed, which has ionic bonding. The halide ion carries a -1 charge, so the formula depends on the valency of the metal.

Halogens are diatomic molecules, meaning they exist as pairs of atoms joined by a single covalent bond.

Cl₂ (aq) + 2Br⁻ (aq) → 2Cl⁻ (aq) + Br₂ (aq)

Chlorine is more reactive than bromine, so it displaces bromide ions from solution. Chlorine gains electrons (reduction) and bromide ions lose electrons (oxidation).

A halogen displacement reaction occurs when a more reactive halogen displaces a less reactive halogen from an aqueous solution of its salt. For example, chlorine displaces bromine from potassium bromide solution.

The noble gases are the Group 0 elements. They are monatomic, colourless, non-flammable gases at room temperature with full outer electron shells, making them extremely unreactive.

The noble gases are unreactive because they have full outer shells of electrons. This configuration is extremely stable, so they do not need to gain or lose electrons to become stable.

True.

As you go down Group 0, atoms get larger, which increases intermolecular forces. More energy is needed to overcome these forces, so boiling points increase.

Helium is used to fill balloons because it is less dense than air and does not burn.

Argon is used in welding because it provides an inert atmosphere. This prevents the hot metal from reacting with oxygen or other gases in the air, which could cause oxidation or weakening of the weld.

False.

Helium has only two electrons in its outer shell (which is also its only shell). All other noble gases have eight electrons in their outer shell.

The density increases going down Group 0. Atoms get larger and heavier as you descend the group, so gases further down have higher densities than those at the top.

Noble gases are used in advertising signs because they glow brightly when a high potential difference is applied under low pressure.

Monatomic means existing as single, individual atoms rather than as molecules. The noble gases (Group 0) are monatomic.

The reactivity series is an ordered list of metals ranked from most to least reactive, based on how easily they lose electrons to form positive ions. It also includes carbon and hydrogen as reference points.

When a metal reacts with cold water, a metal hydroxide and hydrogen gas are produced. For example, calcium reacts with water to form calcium hydroxide and hydrogen.

True.

In a displacement reaction, the more reactive metal takes the place of the less reactive metal. For example, zinc can displace copper from copper oxide.

When a metal reacts with a dilute acid, it forms a metal salt and hydrogen gas.

Carbon and hydrogen are included because they help predict what can happen in reactions. Metals below carbon can be extracted from their ores by heating with carbon. Metals above carbon require electrolysis for extraction.

True.

A more reactive metal loses its outer electrons more easily than a less reactive one. This is why more reactive metals form positive ions more readily and are placed higher in the reactivity series.

The more reactive a metal, the more vigorous its reaction with acid. You can compare the rate of hydrogen gas production — faster, more vigorous bubbling indicates a more reactive metal.

In the reaction between zinc and copper oxide, zinc is the reducing agent because it removes oxygen from the copper oxide.

Metals above carbon cannot be extracted by heating with carbon because carbon is not reactive enough to displace them. Electrolysis uses electrical energy to decompose the molten compound and extract the metal.

The reactivity of Group 1 and Group 2 metals increases as you go down the group. Each successive metal has more electron shells, making it easier to lose outer electrons and form positive ions.

False.

Group 0 elements (the noble gases) are unreactive. They have full outer electron shells, so they do not need to gain or lose electrons.

Transition metals are the block of metals in the middle of the periodic table. They are harder, stronger, denser and much less reactive than Group 1 metals, and can form ions with variable charges.

Group 1 metals react with water, oxygen and halogens, while transition metals either react very slowly or do not react at all.

Group 1 metals are far more reactive than iron and react almost instantly with oxygen in the air to form a dull metal oxide coating. Iron reacts much more slowly and also requires the presence of water to form rust.

True.

Iron is a transition metal and, like other transition metals, can form ions with variable charges. This distinguishes transition metals from Group 1 metals, which always form 1+ ions.

Reactive metals form ionic compounds with reactive non-metals. The metal loses electrons to form a positive ion while the non-metal gains electrons to form a negative ion.

Transition metals have much higher melting points than Group 1 metals. For example, titanium melts at 1,688 °C while potassium melts at only 63.5 °C.

The reactivity of Group 7 elements decreases as you go down the group. Larger atoms have more electron shells, so the outer shell is further from the nucleus and it becomes harder to attract an additional electron.