Lead - Pb

Atomic number

82

Atomic mass

207.2 g.mol ^-1

Electronegativity according to Pauling

1.8

Density

11.34 g.cm^-3 at 20°C

Melting point

327 °C

Boiling point

1755 °C

Vanderwaals radius

0.154 nm

Ionic radius

0.132 nm (+2) ; 0.084 nm (+4)

Isotopes

13

Electronic shell

[ Xe ] 4f¹⁴ 5d¹⁰ 6s^{2 6p2}

Energy of first ionisation

715.4 kJ.mol ^-1

Energy of second ionisation

1450.0 kJ.mol ^-1

Energy of third ionisation

3080.7 kJ.mol ^-1

Energy of fourth ionisation

4082.3 kJ.mol ^-1

Energy of fifth ionisation

6608 kJ.mol ^-1

Discovered by

The ancients

Lead is a soft metal that has known many applications over the years. It has been used widely since 5000 BC for application in metal products, cables and pipelines, but also in paints and pesticides. Lead is one out of four metals that have the most damaging effects on human health. It can enter the human body through uptake of food (65%), water (20%) and air (15%).

Foods such as fruit, vegetables, meats, grains, seafood, soft drinks and wine may contain significant amounts of lead. Cigarette smoke also contains small amounts of lead.

Lead can enter (drinking) water through corrosion of pipes. This is more likely to happen when the water is slightly acidic. That is why public water treatment systems are now required to carry out pH-adjustments in water that will serve drinking purposes.

For as far as we know, lead fulfils no essential function in the human body, it can merely do harm after uptake from food, air or water.

Lead can cause several unwanted effects, such as:
- Disruption of the biosynthesis of haemoglobin and anaemia
- A rise in blood pressure
- Kidney damage
- Miscarriages and subtle abortions
- Disruption of nervous systems
- Brain damage
- Declined fertility of men through sperm damage
- Diminished learning abilities of children
- Behavioural disruptions of children, such as aggression, impulsive behavior and hyperactivity

Lead can enter a foetus through the placenta of the mother. Because of this it can cause serious damage to the nervous system and the brains of unborn children.

Not only leaded gasoline causes lead concentrations in the environment to rise. Other human activities, such as fuel combustion, industrial processes and solid waste combustion, also contribute.

Lead can end up in water and soils through corrosion of leaded pipelines in a water transporting system and through corrosion of leaded paints. It cannot be broken down; it can only converted to other forms.

Lead accumulates in the bodies of water organisms and soil organisms. These will experience health effects from lead poisoning. Health effects on shellfish can take place even when only very small concentrations of lead are present. Body functions of phytoplankton can be disturbed when lead interferes. Phytoplankton is an important source of oxygen production in seas and many larger sea-animals eat it. That is why we now begin to wonder whether lead pollution can influence global balances.

Soil functions are disturbed by lead intervention, especially near highways and farmlands, where extreme concentrations may be present. Soil organisms than suffer from lead poisoning, too.

Lead is a particularly dangerous chemical, as it can accumulate in individual organisms, but also in entire food chains.

For more effects on freshwater ecosystem take a look at lead in freshwater