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The group 2 elements are called the alkaline earth metals. The physical properties and chemical reactivity depend upon the electronic structure of the elements.

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Introduction

Alkesh Chohan                Chemistry

Group 2trends

  • The group 2 elements are called the alkaline earth metals. The physical properties and chemical reactivity depend upon the electronic structure of the elements.

Atomic radius – the distance between nucleus and the outer shell (measured in units nm)

image00.png

Trend – atomic radius increases down the group

Explanation

There are more filled energy levels between the nucleus and the outer electrons therefore the outer electrons are more shielded from the attraction of the nucleus so the electrons in the outer energy levels are further from the nucleus and the atomic radius increases.

As the number of protons in the nucleus increases going down Group 2, you might expect the atomic radius to decrease because the nuclear charge increases. This does not happen, because although the electrons in the inner energy levels become closer to the nucleus, the factors described above have a greater influence on the atomic radius overall.

First ionisation energy – the amount of energy required (Kjmol-1)

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Middle

Electronegativity – the power of an atom to attract electrons in a covalent bond

image02.png

Trend – as you can see, the electronegativity value decreases going down the group.

Explanation

The atomic radius increases therefore the outer electrons are more shielded from the attraction of the nucleus so the bonding electrons are less strongly attracted to the nucleus.

As the number of protons in the nucleus increases going down Group 2, you might expect the electronegativity to increase because the nuclear charge increases. This does not happen, because the factors described above have a greater influence on the electronegativity.

Note that the compounds formed by Group 2 elements are essentially ionic. However, beryllium compounds tend to be atypical, and show some covalent character. This is because the Be2+ ion is relatively very small. As a result, it has a high surface charge density, which allows it to polarise anions very strongly.


Melting point – the temperature (Kelvin)

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Conclusion

Calcium- is found in milk and bones and is reaaalllllllllly good 4 U! (I think)

Strontium- Strontium 90, a radioisotope of Strontium (Sr), can be very dangerous, but it can also be used to treat skin cancer!

Strontium, along with aluminium and zinc are used in alloys to make strong and lightweight bicycle frames

Barium- helps doctors in medicine by blocking x-rays and allowing the digestive system to show up

Radium-Radium had been used to make self-luminous paints for watches, aircraft instrument dials and other instrumentation, but has largely been replaced by cobalt-60, a less dangerous radioactive source. A mixture of radium and beryllium will emit neutrons and is used as a neutron source. Radium is used to produce radon, a radioactive gas used to treat some types of cancer.

A single gram of radium-226 will produce 0.000l millilitres of radon a day. Radium is about one million times more active than uranium. The lab notebooks used by the Curies are too highly contaminated to be safely handled today.

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