CHEM: Talking heads

What would be observed if you put a magnesium ribbon into some hydrochloric acid?

Dissolves quickly, gets hot, gas given off (positive squeaky pop), colourless solution left

What would be observed if you put a magnesium ribbon into some sulfuric acid?

Rapid bubbling, positive squeaky pop, metal dissolves

Observations when lithium is added to water

Effervescence, floats on water and moves around surface leaving white trail behind, metal disappeared

Observations when sodium is added to water

Effervescence, moves on surface water, melted into a ball, faster movement than sodium

Observations when potassium is added to water

Melted into ball, moved around fast on surface of water, burned with lilac flame

What would be observed if you added iron to hydrochloric/sulfuric acid?

HCl: Very slow bubbling

H2SO4: Slow reaction, small bubbles

What would happen if you added zinc to hydrochloric/sulfuric acid?

HCl: Bubbles given off, metal slowly dissolves

H2SO4: Bubbles slowly, metal dissolves, colourless solution

What are the group 1 metals known as?

Alkali metals because they form alkaline solutions when they react with water

What are some common characteristics of group 1 metals?

Soft, can easily be cut with a knife

Relatively low densities and low melting points

Very reactive

Why are group 1 metals so reactive?

They only have to lose one electron to have a full outer shell

Equation for group 1 metals with water

2[M] (s) + 2H2O (l) → 2[M]OH (aq) + H2 (g)

What forms when a group 1 metal reacts with water?

A colourless, aqueous solution

Describe the trend in the reactions of alkali metals with water as you descend the group.

The reactions get more vigorous as you descend the group.

Why do the first 3 alkali metals float on the surface of the water?

They are less dense than water

Describe and explain the trend in reactivity in group 1 metals

They get more reactive as you descend the group.

The atoms are larger so have more outer shells and thus the outermost electron gets further from the nucleus. The force of attraction between the nucleus and outer electron gets weaker so there is less energy required to overcome it and the electron is more easily lost.

What are halogens?

Elements in group 7

What does fluorine look like at room temperature?

Yellow poisonous gas

Very reactive

What does chlorine look like at room temperature?

Pale yellow-green, dense gas

Reactive and poisonous

Colour of chlorine in solution

Pale green

What does bromine look like at room temperature?

Red-brown dense liquid

Volatile (evaporates easily)

Colour of bromine in solution

Orange

What does iodine look like at room temperature?

Grey, shimmery, crystalline solid

Sublimes to form a purple vapour

Colour of iodine in solution

Dark brown

What do halogens exist as?

Diatomic molecules

Describe and explain the trend in melting and boiling points of halogens.

Melting and boiling points increase as you descend the group

The intermolecular forces become stronger as the atoms get larger so more energy is required to overcome these forces.

Why do halogens get less reactive as you descend the group?

The atomic mass of the halogens increases and they increase in electron shells. The halogen atom must gain an electron to get a full outer shell and become stable. As the outer shell gets further away from the nucleus, the force of attraction between the two decreases, so it is more difficult to gain an electron.

What structure forms when a halogen reacts with a metal?

An ionic compound which is a metal halide salt

What structure forms when a halogen reacts with a non-metal?

A simple molecular covalent structure, e.g. halogens react with hydrogen to form hydrogen halides like hydrogen chloride.

Place these elements in order of most to least reactive: Iodine, Chlorine, Bromine

Chlorine, bromine, iodine

What is the reactivity series (including carbon) from most to least reactive?

Potassium, sodium, lithium, calcium, magnesium, aluminium, carbon, zinc, iron, hydrogen, copper, silver, gold

What happens in a displacement reaction?

A more reactive element takes the place of a less reactive one in a compound.