Unit 2 Chemistry

What are isotopes?

Isotopes are different forms of the same element which have the same atomic number but a different mass number.

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What is ionic bonding?

Ionic bonding is the losing or gaining of electrons to form charged particles in atoms.

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What is the charge of metal ions?

Positive

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What is the charge of non-metal ions?

Negative

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Describe an ionic structure

Ionic lattices contain strong electrostatic forces of attraction between oppositely charged ions.

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Why do ionic structures have a high melting and boiling points?

There are strong electrostatic attractions between the oppositely charged ions which means that it takes a lot of energy to overcome these bonds.

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When do ions carry a charge?

When they are molten or dissolved in water.

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What is the overall charge of any ionic compound?

0

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What are covalent bonds?

Covalent bonds are strong bonds where atoms share the electrons from the outer shell.

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Why do group 4 elements not make ions?

Group 4 ions are too unstable because of their 4+ or 4- charge.

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Describe the properties of simple molecular covalent structures.

Covalent bonds are very strong but covalent structures have weak intermolecular forces which means that these bonds take only a small amount of energy to overcome, so the melting and boiling points are low.

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What is meant by diatoms?

Diatoms are atoms of the same element that share one or more covalent bonds, so therefore exist as diatoms. For example, O2 is a diatom.

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Describe the properties of giant covalent structures.

Covalent structures contain atoms which are bonded to each other with strong covalent bonds. They have a high melting and boiling point because it takes a lot of energy to overcome these bonds and they do not conduct because there is no charged ions.

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What are the properties of diamond?

Diamond is made up of carbon, which forms 4 strong covalent bonds, in a rigid covalent lattice. This means that diamond is very hard so is often used for drill tips or jewellery, because it doesn't scratch or break.

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What are the properties of graphite?

Each carbon atom only forms 3 covalent bonds so they are arrange in layers that can slide over each other, making graphite very soft and slippery. Graphite contains delocalised electrons which are free to move around the structure and carry a charge.

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What are delocalised electrons?

Delocalised, or free, electrons come from the outer shell in every metal atom and are shared between the atoms so are free to move around the structure.

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Describe the properties of a metallic lattice.

Metals are good conductors of heat and electricity because the delocalised electrons move about the lattice and carry a charge. Also, they create strong electrostatic forces which makes the metal very hard and strong with high melting/boiling points.

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What are alloys?

Alloys are a mixture of a metal with one other element.

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Why are alloys used?

Alloys are used because they are of different sized atoms so the layers of metal that were previously free to slide over each other are distorted and do not do so easily, making alloys harder.

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Give an example of an alloy and it's properties.

Steel is an iron-carbon alloy and is used in cutlery and industry because it is hard, cheap, corrosive resistant and strong.

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What are nanoparticles?

Nanoparticles are very, very small structures only a few atoms long.

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Unit 2 Chemistry

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